basic principle, working and instrumentation of...

[Nikita H. Patel / Ph. D. Thesis / Sardar Patel University/ July−2015] Page 57

CHAPTER 2

Basic Principle, Working

and Instrumentation of

Experimental Techniques


2.1 Introduction

In this chapter, a brief description of basic principle, working and experimental

set up of instrumentation used for studying structural, optical, magnetic and thermal

properties of synthesized undoped and magnetic (Mn, Ni and Co) doped CdS

nanoparticles are described and listed below:

1. Energy Dispersive Analysis of X−rays (EDAX)

2. X−ray Diffraction (XRD)

3. Transmission Electron Microscopy (TEM)

4. UV−Vis−NIR Spectroscopy

5. Spectrofluorometer−PL (Photoluminescence)

6. Fourier Transform Infrared Spectroscopy (FTIR)

7. Raman Spectroscopy

8. Gouy Balance Method

9. Vibrating Sample Magnetometer (VSM)

10. Thermogravimetry Analysis (TGA)

2.2 Characterization Techniques

2.2.1 Energy Dispersive Analysis of X−rays (EDAX)

2.2.1.1 Basic Principle

EDAX is an analytical technique used for elemental analysis or chemical

characterization of a sample. It is based on the investigation of a sample through

interactions between electromagnetic radiation and matter, analyzing X−rays emitted by

the matter in response to being hit with the electromagnetic radiation. Its characterization

capabilities are due in large part to the fundamental principle that each element has a

unique atomic structure allowing X−rays that are characteristic of an element's atomic

structure to be identified uniquely from each other.


To stimulate the emission of characteristic X−rays from a specimen, a high

energy beam of charged particles such as electrons or a beam of X−rays, is focused with

the sample being studied. At rest, an atom within the sample contains ground state (or

unexcited) electrons in discrete energy levels or electron shells bound to the nucleus. The

incident beam may excite an electron in an inner shell, ejecting it from the shell while

creating an electron hole where the electron was. A position vacated by an ejected inner

shell electron is eventually occupied by a higher energy electron from an outer shell and

the difference in energy between the higher energy shell and the lower energy shell may

be released in the form of an X−ray as shown in fig. 2.1. The amount of energy released

by the transferring electron depends on which shell it is transferring from, as well as

which shell it is transferring to. The number and energy of the X−rays emitted from a

specimen can be measured by an energy dispersive spectrometer. As the energy of the

X−ray is characteristic of the difference in energy between the two shells, and of the

atomic structure of the element from which they were emitted, this allows the elemental

composition of the specimen to be measured.

Fig. 2.1 Principle of EDAX.


The position of the peak with appropriate energies gives information about the

qualitative composition of the sample. The number of the X−ray quanta is the measure

for the concentration of the elements (peak height). There is not linear connection

between quantum numbers and concentration portions of the elements. The concentration

calculation needs the net count rates of from it derived measured variables.

2.2.1.2 Experimental Set Up

Fig. 2.2 shows an experimental arrangement of EDAX attached to an SEM. It

consists of four primary components:

1. Beam source

2. X−ray detector

3. Pulse processor

4. Analyzer

EDAX systems are most commonly found on scanning electron microscopes and

electron microprobes. Scanning electron microscopes are equipped with a cathode and

magnetic lenses to create and focus a beam of electrons. The energy of the electron beam

has to be selected to give a compromise between the requirements of resolution and

X−ray production efficiency. The X−radiation excited in the specimen was analyzed in

two fully focusing crystal spectrometers. The EDS X−ray detector measures the relative

abundance of emitted X−rays versus their energy. The detector is typically lithium drifted

silicon, solid state device. When an incident X−ray strikes the detector, it creates a charge

pulse that is proportional to the energy of X−ray. The charge pulse is converted to a

voltage pulse by a charge−sensitive preamplifier. The signal is then sent to a

multichannel analyzer where the pulses are sorted by voltage. The energy, as determined

from the voltage measurement, for each incident X−ray is sent to a computer for display

and further data evaluation. The spectrum of X−ray energy versus counts is evaluated to

determine the elemental composition of the sample volume.

Elements of low atomic number are difficult to detect by EDAX. The Si (Li)

detector is often protected by a Beryllium (Be) window. The absorption of the soft


X−rays by the Be precludes the detection of elements below an atomic number of 11

(Na). In windowless systems, elements with as low atomic number as 4 (Be) have been

detected, but the problems involved get progressively worse as the atomic number is

reduced [1−2].

Fig. 2.2 Experimental set up of Energy dispersive analysis of X−rays (EDAX).

Specifications:

Model : JOEL JSM−5610

Resolution : With LaB6 filament 2 nm at 30 kV, with W filament 3.5 nm at 30 kV

Accelerating Voltage : 0.2 to 30 kV

Magnification : upto 2,50,000 X

2.2.2 X−ray Diffraction (XRD)


X−ray Powder Diffraction (XRD) is an efficient analytical technique used

determination of grain size, composition of solid solution, lattice constants, and degree of

crystallinity in a mixture of amorphous and crystalline substances [3]. It is a common

[Nikita H. Patel / Ph. D. Thesis / Sardar Patel University/ July−2015] 2

technique for the study of crystal structures, atomic spacing, crystallite sizes, stress

analysis, lattice parameters, quantitative phase analysis and can provide information on

unit cell dimensions. This information is important for relating the production of a

material to its structure and hence its properties.

X−ray diffraction is based on constructive interference of monochromatic X−rays

and a crystalline sample. These X−rays are generated by a cathode ray tube, filtered to

produce monochromatic radiation, collimated to concentrate, and directed toward the

sample. The interaction of the incident rays with the sample produces constructive

interference (and a diffracted ray) when conditions satisfy Bragg's Law (nλ = 2d sinθ) as

shown in fig. 2.3. These diffracted X−rays are then detected, processed and counted. By

scanning the sample through a range of 2θ angles, all possible diffraction directions of the

lattice should be attained due to the random orientation of the powdered material.

Conversion of the diffraction peaks to d−spacings allows identification of the mineral

because each mineral has a set of unique d−spacings. Typically, this is achieved by

comparison of d−spacings with standard reference patterns i.e JCPDF files.

Fig. 2.3 A schematic of Bragg’s reflection from a crystal.


X−ray diffractometers consists of three basic elements:

1. X−ray tube


2. Sample holder

3. X−ray detector.

X−rays are generated in a cathode ray tube by heating a filament to produce

electrons, accelerating the electrons toward a target by applying a voltage, and

bombarding the target material with electrons. When electrons have sufficient energy to

dislodge inner shell electrons of the target material, characteristic X−ray spectra are

produced. These spectra consist of several components, the most common being Kα and

Kβ. Kα consists, in part, of Kα1 and Kα2. Kα1 has a slightly shorter wavelength and twice

the intensity as Kα2. The specific wavelengths are characteristic of the target material (Cu,

Fe, Mo, Cr). Filtering, by foils or crystal monochrometers, is required to produce

monochromatic X−rays needed for diffraction. Kα1and Kα2 are sufficiently close in

wavelength such that a weighted average of the two is used. Copper is the most common

target material for single−crystal diffraction, with CuKα radiation = 0.5418Å.

These X−rays are collimated and directed onto the sample. As the sample and

detector are rotated, the intensity of the reflected X−rays is recorded. When the geometry

of the incident X−rays impinging the sample satisfies the Bragg Equation, constructive

interference occurs and a peak in intensity occurs. A detector records and processes this

X−ray signal and converts the signal to a count rate which is then output to a device such

as a printer or computer monitor.

The geometry of an X−ray diffractometer is such that the sample rotates in the

path of the collimated X−ray beam at an angle θ while the X−ray detector is mounted on

an arm to collect the diffracted X−rays and rotates at an angle of 2θ as shown in fig. 2.4.

In the experiment goniometer is used to maintain the angle and rotate the sample in the

path of X−ray source.


Fig. 2.4 Schematic representation of sample mounted on a goniometer stage, which can

be rotated about one or more axes, and a detector which travels along the

focusing circle in the Bragg−Brentano geometry.

The complete experimental set−up is shown in fig. 2.5. The intensity of diffracted

X−rays is continuously recorded as the sample and detector rotate through their

respective angles. A peak in intensity occurs when the mineral contains lattice planes

with d−spacings appropriate to diffract X−rays at that value of θ. Although each peak

consists of two separate reflections (Kα1 and Kα2), at small values of 2θ the peak locations

overlap. Greater separation occurs at higher values of θ. Typically, these combined peaks

are treated as one.

Results are commonly presented as peak positions at 2θ and X−ray counts

(intensity) in the form of a table. Intensity is either reported as peak height intensity, that

intensity above background, or as integrated intensity, the area under the peak. The

relative intensity is recorded as the ratio of the peak intensity to that of the most intense

peak For determination of an unknown compound we can follow the below procedure:

The d−spacing of each peak is then obtained by solution of the Bragg equation for the

appropriate value of λ. Once all d−spacings have been determined, compare the d−


spacing of the unknown to those of known materials. Because each mineral has a unique

set of d−spacings, matching these d−spacings provides an identification of the unknown

sample. A systematic procedure is used by ordering the d−spacings in terms of their

intensity beginning with the most intense peak [4−7].

Specification:

Model : Philips Xpert MPD XRD

Source : Cu target X−Ray tube

X−Ray Power : 2 kW

Detector : Xe filled Count rate or Proportional detector

Software : JCPDF database for powder diffractometry

goniometer

Operation Modes : Vertical & Horizontal

Accuracy : ± 0.0025

2θ° Measurement

range

: 3o

to 136o

Diffractometer radius : 130 to 230 mm

Fig. 2.5 Experimental set up of X−ray diffractometer.


2.2.3 Transmission Electron Microscopy (TEM)


Transmission electron microscopy (TEM) is a technique used for analyzing the

morphology, defects, crystallographic structure, particle size and even composition of a

specimen. In this technique a beam of electrons is transmitted through an ultra thin

specimen, interacting with the specimen as it passes through. An image is formed from

the interaction of the electrons transmitted through the specimen; the image is magnified

and focused onto an imaging device, such as a fluorescent screen, on a layer of

photographic film, or to be detected by a sensor such as a CCD camera. The transmission

electron microscope (TEM) operates on the same basic principles as the light microscope

but uses electrons instead of light. What you can see with a light microscope is limited by

the wavelength of light. TEM use electrons as "light source" and their much lower

wavelength make it possible to get a resolution a thousand times better than with a light

microscope.

TEMs are capable of imaging at a significantly higher resolution than light

microscopes, owing to the small De Broglie wavelength of electrons. This enables the

instrument's user to examine fine detail even as small as a single column of atoms, which

is tens of thousands times smaller than the smallest resolvable object in a light

microscope. TEM forms a major analysis method in a range of scientific fields, in both

physical and biological sciences. TEMs find application in cancer research, virology,

materials science as well as pollution and semiconductor research. At smaller

magnifications TEM image contrast is due to absorption of electrons in the material, due

to the thickness and composition of the material. At higher magnifications complex wave

interactions modulate the intensity of the image, requiring expert analysis of observed

images. Alternate modes of use allow for the TEM to observe modulations in chemical

identity, crystal orientation, electronic structure and sample induced electron phase shift

as well as the regular absorption based imaging.



TEM offers two methods of specimen observation as shown in fig. 2.6.

1. Image mode

2. Diffraction mode

In image mode, the condenser lens and aperture will control electron beam to hit

the specimen, the transmitted beam will be focused and enlarged by objective and

projector lens and form the image in the screen, with recognizable details related to the

sample microstructure. In diffraction mode, an electron diffraction pattern is obtained on

the fluorescent screen, originating from the sample area illuminated by the electron beam.

The diffraction pattern is entirely equivalent to an X−ray diffraction pattern. A single

crystal will produce a spot pattern on the screen and polycrystal will produce a powder or

ring pattern. The microstructure, e.g. the grain size, and lattice defects are studied by use

of the image mode, while the crystalline structure is studied by the diffraction mode.

Fig. 2.6 Shows two different operations of TEM.


Image Modes of TEM

There are two primary image modes in TEM differ in the manner in which way an

objective aperture is used as a filter in electric optics system are

1. Bright field microscopy

2. Dark field microscopy

In bright field imaging, the image of a thin sample is formed by the electrons that

pass the film without diffraction, the diffracted electrons being stopped by a diaphragm.

In the corresponding dark field imaging mode, a diffracted beam is used for imaging. The

technique known as bright Field is particularly sensitive to extended crystal lattice defects

in an otherwise ordered crystal, such as dislocations. The electron rays corresponding to

bright field and dark field imaging are shown in fig. 2.7 respectively and the experimental

set up for transmission electron microscope is shown in fig. 2.8.

Fig. 2.7 Two image modes of TEM.


Fig. 2.8 Experimental set up of Transmission Electron Microscope.

Specifications:

Model : TEM with CCD camera Philips, Tecnai 20

Electron Source : W emitter and LaB6

Accelerating Voltage : 200 kV

Point Resolution : 0.27 nm or better

Line Resolution : 2.0 nm or better

Magnification : 25X to 750000X or higher

2.2.4 UV−Vis−NIR Spectroscopy


The instrument used in ultraviolet−visible spectroscopy is called a UV−Vis−NIR

Spectrophotometer. Spectrophotometer provides a means for analyzing liquids, gases and

solids through the use of radiant energy in the far and near ultraviolet, visible and near

infrared regions of the electromagnetic spectrum. Accordingly, the predetermined

electromagnetic radiation wavelengths for ultra−violet (UV), visible (Vis) and near

infra−red (NIR) radiation are defined as follows:

UV radiation: 300 to 400 nm

Vis radiation: 400 to 765 nm

NIR radiation: 765 to 3200 nm


The instrument operates by passing a beam of light through a sample and

measuring wavelength of light reaching a detector. The wavelength gives valuable

information about the chemical structure and the intensity is related to the number of

molecules, means quantity or concentration. Analytical information can be revealed in

terms of transmittance, absorbance orreflectance of energy in the wavelength range

between 160 and 3500 mill microns [1].

Light is quantized into tiny packets called photons, the energy of which can be

transferred to an electron upon collision. However, transfer occurs only when the energy

level of the photon equals the energy required for the electron to get promoted onto the

next energy state, for example from the ground state to the first excitation state. This

process is the basis for absorption spectroscopy. Generally, light of a certain wavelength

and energy is illuminated on the sample, which absorbs a certain amount of energy from

the incident light. The energy of the light transmitted from the sample afterwards is

measured using a photo detector, which registers the absorbance of the sample. A

spectrum is a graphical representation of the amount of light absorbed or transmitted by

matter as a function of wavelength. A UV−Vis−NIR spectrophotometer measures

absorbance or transmittance from the UV range to which the human eye is not sensitive

to the visible wavelength range to which the human eye is sensitive. Bouguer−Beer law

as shown in fig. 2.9 is a basic principle of quantitative analysis, is also called the

Lambert−Beer rule. The following relationship is established when light with intensity Io

is directed at a material and light with intensity I is transmitted.

Fig. 2.9 Bouguer−Beer Rule.


In this instance the value I/Io is called transmittance (T) and the value I/Io*100 is

called transmission rate (T%). The value log (1/T) = log (Io/I) is called absorbance (Abs).

T = I/Io = 10−kcl

Abs = log (1/T) = log(Io/I) = −kcl

Here k is proportionality constant and & l = length of light path through the cuvette in

cm. As can be seen from the above formulas, transmittance is not proportional to sample

concentration. However, absorbance is proportional to sample concentration (Beer's law)

along with optical path (Bouguer's law). In addition, when the optical path is 1cm and the

concentration of the target component is 1mol/l, the proportionality constant is called the

molar absorption coefficient and expressed using the symbol ε. The molar absorption

coefficient is a characteristic value of a material under certain, specific conditions.

Finally, stray light, generated light, scattered light, and reflected light must not be present

in order for the Bouguer−Beer rule to apply.


Spectrophotometers consist of a number of fundamental components: Light

Sources (UV and VIS), monochromator (wavelength selector), sample holder, a detector,

signal processor and readout. The radiation source used is often a tungsten filament, a

deuterium arc lamp which is continuous over the ultraviolet region, and more recently

light emitting diodes (LED) and xenon arc lamps for the visible wavelengths. The

detector is typically a photodiode or a CCD. Photodiodes are used with monochromators,

which filter the light so that only light of a single wavelength reaches the detector. When

measuring absorbance at the UV spectrum, the other lamp has to be turned off. The same

goes when measuring visible light absorbance. Fig. 2.10 shows schematic diagram of

UV−Vis−NIR Spectrophotometer.


Fig. 2.10 Schematic diagram of UV−Vis−NIR Spectrophotometer.

The light source is a monochromator; the light is split into two equal intensity

beams by a half mirrored device before it reaches the sample. One beam, the sample

beam, passes through a small transparent container (cuvette) containing a solution of the

compound being studied in a transparent solvent. The other beam, the reference, passes

through an identical cuvette containing only the solvent. The containers for the sample

and reference solution must be transparent to the radiation which will pass through them.

Quartz or fused silica cuvettes are required for spectroscopy in the UV−Vis−NIR region.

The light sensitive detector follows the sample chamber and measures the intensity of

light transmitted from the cuvettes and passes the information to a meter that records and

displays the value to the operator on an LCD screen. The intensities of these light beams

are then measured by electronic detectors and compared. Some UV−Vis

spectrophotometry has two detectors the phototube and the photomultiplier tube. The

sample and reference beam are measured at the same time. The intensity of the reference

beam, which should have suffered little or no light absorption, is defined as I0. The

intensity of the sample beam is defined as I. Over a short period of time, the Spectrometer


automatically scans all the component wavelengths in the manner described. The

ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion

is from 400 to 800 nm. Therefore, this method is excellent to both determine the

concentration and identify the molecular structure or the structural changes.

Spectrophotometer is also useful to study the changes in the vibration and conformation

energy levels after and before an interaction with a substrate, or another molecule [8].

Fig. 2.11 shows experimental set−up of UV−Vis−NIR Spectrophotometer.

Fig. 2.11 Experimental set up of UV−Vis−NIR Spectrophotometer.

Specifications:

Model : UV−Vis−NIR Spectrometer Perkin Elmer Lambda 19

Lamp : Deuterium (UV), Tungsten−Halogen (Vis/NIR)

Detectors : Photomultiplier tube for UV−Vis, Lead−Sulphide cell (PbS) for NIR

Wavelength Range : 185−3200 nm for Absorbance/transmission and 200−2500 nm for

reflectance

Scan Speed : 0.3 to 1200 nm/min

Wavelength accuracy : ± 0.15 nm for UV/Vis & ± 0.6 nm for NIR

Base line flatness : ± 0.001Å, 4 nm slit

Ordinate mode : Scan, time drive, wavelength programming, concentration

Photometric accuracy : ± 0.003 Å or ± 0.08% T


2.2.5 Spectrofluorometer−PL (Photoluminescence)


Photoluminescence spectroscopy is a contactless, versatile, nondestructive,

powerful optical method of probing the electronic structure of materials. Light is directed

onto a sample, where it is absorbed and imparts excess energy into the material in a

process called photo−excitation. One way this excess energy can be dissipated by the

sample is through the emission of light, or luminescence. In the case of photo−excitation,

this luminescence is called photoluminescence. Thus photoluminescence is the

spontaneous emission of light from a material under optical excitation. This light can be

collected and analyzed spectrally, spatially and also temporally. The intensity and

spectral content of this photoluminescence is a direct measure of various important

material properties.

Photo excitation causes electrons within the material to move into permissible

excited states. When these electrons return to their equilibrium states, the excess energy

is released and may include the emission of light (a radiative process) or may not (a non

radiative process) as shown in fig. 2.12. The energy of the emitted light

(photoluminescence) relates to the difference in energy levels between the two electron

states involved in the transition between the excited state and the equilibrium state. The

quantity of the emitted light is related to the relative contribution of the radiative process.

PL spectroscopy gives information only on the low lying energy levels of the investigated

system. In semiconductor systems, the most common radiative transition is between

states in the conduction and valence bands, with the energy difference being known as

the bandgap. During a PL spectroscopy experiment, excitation is provided by laser light

with an energy much larger than the optical band gap. The photo excited carriers consist

of electrons and holes, which relax toward their respective band edges and recombine by

emitting light at the energy of the band gap. Radiative transitions in semiconductors may

also involve localized defects or impurity levels therefore the analysis of the PL spectrum

leads to the identification of specific defects or impurities, and the magnitude of the PL

signal allows determining their concentration. The respective rates of radiative and


nonradiative recombination can be estimated from a careful analysis of the temperature

variation of the PL intensity and PL decay time. At higher temperatures nonradiative

recombination channels are activated and the PL intensity decreases exponentially. Thus

photoluminescence is a process of photon excitation followed by photon emission and

important for determining band gap, purity, crystalline quality and impurity defect levels

of semiconducting material. It also helps to understand the underlying physics of the

recombination mechanism.

PL spectrum is quite different from absorption spectrum in the sense that

absorption spectrum measures transitions from the ground state to excited state, while

photoluminescence deals with transitions from the excited state to the ground state. The

period between absorption and emission is typically extremely short. An excitation

spectrum is a graph of emission intensity versus excitation wavelength which looks very

much like an absorption spectrum. The value of wavelength at which the molecules

absorbs energy can be used as the excitation wavelength which provide a more intense

emission at a red shifted wavelength, with a value usually twice of the excitation

wavelength.

Fig. 2.12 Principle of photoluminescence spectroscopy (PL).



A spectrofluorometer is an analytical instrument used to measure and record the

fluorescence of a sample. While recording the fluorescence, the excitation, emission or

both wavelength may be scanned. With additional accessories, variation of signal with

time, temperature, concentration, polarization, or other variables may be monitored. Fig.

2.13 shows the block diagram of fluorescence spectrometer. Fluorescence spectrometers

use laser sources, which contains wavelength selectors, sample illumination, detectors

and corrected spectra.

Fig. 2.13 Block diagram of fluorescence spectrometer.

Illuminator source:- The continuous light source is 150 W ozone free xenon arc lamp.

Light from the lamp is collected by a diamond turned elliptical mirror, and then focused

on the entrance slit of the excitation monochromator. The lamp housing is separated from

the excitation monochromator by a quartz window. This vents heat out of the instrument,

and protects against the unlikely occurrence of lamp failure. Resolution over the entire

spectral range and minimize spherical aberrations and re diffraction.


Monochromators:- It contains two monochromators : Excitation monochromator and

Emission monochromator. They use all reflective optics to maintain high resolution over

the entire spectral range, and minimize spherical aberrations and re diffraction.

Gratings:- The essential part of a monochromator is a reflection grating. A grating

disperses the incident light by means of its vertical grooves. A spectrum is obtained by

rotating the gratings contain 1200 grooves mm−1

, and are blazed at 330 nm (excitation) at

500 nm (emission). Each grating is coated with MgF2 for protection against oxidation.

Slits:- The entrance and exit ports of each monochromator have continuously adjustable

slits. The width of the slits on the excitation monochromator determines the band pass of

light incident on the sample. The emission monochromator’s slits control the intensity of

the fluorescence signal recorder by the signal detector. When setting slit width, the trade

off is intensity of signal versus spectral resolution. The wider the slits are, the more light

falls on the sample and detector, but the resolution decreases. The narrower slits are, the

higher the resolution gets but at the expense of signal.

Shutters:- An excitation shutter is located just after the excitation monochromator’s exit

slit. The shutter protects sample from photo bleaching or photo degradation from

prolonged exposure to the light source. An emission shutter is placed just before the

emission monochromator’s entrance and protects the detector from bright light.

Sample compartment:- The sample compartment accommodates various optional

accessories, as well as fiber optic bundles to take the excitation beam to a remote sample

and return the emission beam to the emission monochromator.

Detectors:- It contains two detectors: Signal detector and reference detector. The signal

detector is a photon conting detector. This detector is an R928P photomultiplier tube,

which sends the signal to a photon counting module. The reference detector monitors the

xenon lamp, in order to correct for wavelength and time dependent output of the lamp.

This detector is a UV enhance silicon photodiode, which is just before the sample

compartment.


Computer Control:- The entire control of the FluoroMax−4 originates in your PC with

our revolutionary new Fluor Essenc software and is transmitted through a serial link. On

start up, the system automatically calibrates and presents itself for new experiments or

stored routines instantly called from memory. Fig. 2.14 shows Experimental set up of

Spectrofluorometer.

Fig. 2.14 Experimental set up of SHIMADZU RF−5301PC Spectrofluorometer.

Specifications:

Light source : 150 W Xenon lamp. Ozone resolving type lamp housing

Excitation and

emission

monochromators

: Concave, blazed holographic grating, F/2.5, 1300

grooves/mm

Wavelength scale : 220−990 nm

Measuring wavelength

range

: 220−750 nm and 0 order as standard. 220−900 nm with the

optional R928 photomultiplier

Spectral band with : 6 step selection of 1.5, 3, 5, 10, 15 and 20 nm. (6 nm

bandwidth is available for half sample height on the

excitation side only).


Wavelength accuracy : ±1.5 nm

Light source

compensation

: Dynode feedback system with monochromatic light

monitoring

Sensitivity : The S/N ratio is 150 or higher for the Raman line of distilled

water (350 nm excitation wavelength, 5 nm spectral

bandwidth, and 2 second response for 98% of the full scale)

Wavelength scanning : 7 step selection of Survey (about 5500 nm/min), Super

(about 3000 nm/min)

Very fast, Fast, Medium, Slow and Very slow

Wavelength slewing

speed

: About 20,000 nm/min.

Response : 8 step selection of 0.02, 0.03, 0.1, 0.25, 0.5, 2, 4 and 8

seconds for 98% of the full scale

Sensitivity selection : 2 steps of HIGH and LOW (The sensitivity at HIGH is

about 50 times that of LOW)

2.2.6 Fourier Transform Infrared Spectroscopy (FTIR)


Infrared spectroscopy is an important technique in organic chemistry. It is an

easy way to identify the presence of certain functional groups in a molecule. Also, one

can use the unique collection of absorption bands to confirm the identity of a pure

compound or to detect the presence of specific impurities. Analysis by infrared

spectroscopy is based on the fact that molecules have specific frequencies of internal

vibrations. These frequencies occur in the infrared region of the electromagnetic

spectrum: ~ 4000 cm−1

to ~ 200 cm−1

.

When a sample is placed in a beam of infrared radiation, the sample will absorb

radiation at frequencies corresponding to molecular vibrational frequencies, but will

transmit all other frequencies. The frequencies of radiation absorbed are measured by an

infrared spectrometer, and the resulting plot of absorbed energy vs. frequency is called


infrared spectrum of the material. Identification of a substance is possible because

different materials have different vibrations and yield different infrared spectra.

Furthermore, from the frequencies of the absorption it is possible to determine whether

various chemical groups are present or absent in a chemical structure. In addition to the

characteristic nature of the absorption, the magnitude of the absorption due to a given

species is related to the concentration of that species.

Fourier Transform Infrared (FTIR) spectrometry was developed in order to

overcome the limitations encountered with dispersive instruments. The main difficulty

was the slow scanning process. A method for measuring all of the infrared frequencies

simultaneously, rather than individually, was needed. A solution was developed which

employed a very simple optical device called an interferometer. The interferometer

produces a unique type of signal which has all of the infrared frequencies “encoded” into

it. The signal can be measured very quickly, usually on the order of one second or so.

Thus, the time element per sample is reduced to a matter of a few seconds rather than

several minutes. Most interferometers employ a beam splitter which takes the incoming

infrared beam and divides it into two optical beams. One beam reflects off of a flat mirror

which is fixed in place. The other beam reflects off of a flat mirror which is on a

mechanism which allows this mirror to move a very short distance (typically a few

millimeters) away from the beam splitter. The two beams reflect off of their respective

mirrors and are recombined when they meet back at the beam splitter. Because the path

that one beam travels is a fixed length and the other is constantly changing as its mirror

moves, the signal which exits the interferometer is the result of these two beams

“interfering” with each other. The resulting signal is called an interferogram which has

the unique property that every data point (a function of the moving mirror position)

which makes up the signal has information about every infrared frequency which comes

from the source. This means that as the interferogram is measured; all frequencies are

being measured simultaneously. Thus, the use of the interferometer results in extremely

fast measurements. Because the analyst requires a frequency spectrum (a plot of the

intensity at each individual frequency) in order to make identification, the measured

interferogram signal cannot be interpreted directly. A means of “decoding” the individual


frequencies is required. This can be accomplished via a well known mathematical

technique called the Fourier transformation. This transformation is performed by the

computer which then presents the user with the desired spectral information for analysis.


The basic components of an FTIR are shown schematically in fig. 2.15. The

infrared source emits a broad band of different wavelength of infrared radiation. The IR

source used in the Temet GASMET FTIR CR−series is a SiC ceramic at a temperature of

1550 K. The IR radiation goes through an interferometer that modulates the infrared

radiation. The interferometer performs an optical inverse Fourier transform on entering

IR radiation. The modulated IR beam passes through the gas sample where it is absorbed

to various extents at different wavelengths by the various molecules present. Finally, the

intensity of the IR beam is detected by a detector, which is a liquid nitrogen cooled MCT

(Mercury−Cadmium−Telluride) detector in the case of the Temet GASMET FTIR CR

series. The detected signal is digitised and Fourier transformed by the computer to get the

IR spectrum of the sample gas.

Fig. 2.15 Basic components of FTIR.

1. The Source:- Infrared energy is emitted from a glowing black body source. This beam

passes through an aperture which controls the amount of energy presented to the sample

(and, ultimately, to the detector).

2. The Interferometer:- The beam enters the interferometer where the “spectral

encoding” takes place. The resulting interferogram signal then exits the interferometer.

3. The Sample:- The beam enters the sample compartment where it is transmitted

through or reflected off of the surface of the sample, depending on the type of analysis


being accomplished. This is where specific frequencies of energy, which are uniquely

characteristic of the sample, are absorbed.

4. The Detector:- The beam finally passes to the detector for final measurement. The

detectors used are specially designed to measure the special interferogram signal.

5. The Computer:- The measured signal is digitized and sent to the computer where the

Fourier transformation takes place. The final infrared spectrum is then presented to the

user for interpretation and any further manipulation. Fig. 2.16 shows experimental set up

of FTIR spectrometer.

Fig. 2.16 Experimental set up of FTIR spectrometer.

Specifications:

Model : Perkin Elmer Spectrum GX

Sample : Solid, Liquid or Gas

Operating Mode : NIR and MIR

Scan Range : 15600 to 30 cm−1

Optical system : Source NIR: 15,200 – 1,200 cm−1


Beam splitter KBr : 7,800 − 370 cm−1

Detector MIRTGS : 10,000 − 220 cm−1

Beam splitter KBr : 7,800 − 370 cm−1

OPD Velocity : 0.20 cm/s

Inferogram

Direction

: Bi−Direction

Scan Time : 20 scan/second

Resolution : 0.15cm−1

Single Beam/Ratio : Single

Detector : MIRTGS

2.2.7 Raman Spectroscopy


Raman spectroscopy is a useful technique for the identification of a wide range of

substances–solids, liquids and gases. It is a straightforward, non destructive technique

requiring no sample preparation. Raman spectroscopy involves illuminating a sample

with monochromatic light and using a spectrometer to examine light scattered by the

sample.

Raman spectroscopy is a spectroscopic technique based on inelastic scattering of

monochromatic light, usually from a laser source. Inelastic scattering means that the

frequency of photons in monochromatic light changes upon interaction with a sample.

Photons of the laser light are absorbed by the sample and then reemitted. Frequency of

the reemitted photons is shifted up or down in comparison with original monochromatic

frequency, which is called the Raman effect. This shift provides information about

vibrational, rotational and other low frequency transitions in molecules. This effect is

based on molecular deformations in electric field E determined by molecular

polarizability (α). The laser beam can be considered as an oscillating electromagnetic

wave with electrical vector E. Upon interaction with the sample it induces electric dipole

moment P = αE which deforms molecules. Because of periodical deformation, molecules


start vibrating with characteristic frequency υm. Monochromatic laser light with

frequency υo excites molecules and transforms them into oscillating dipoles. Such

oscillating dipoles emit light of three different frequencies as shown in fig. 2.17 when:

1. A molecule with no Raman active modes absorbs a photon with the frequency υo. The

excited molecule returns back to the same basic vibrational state and emits light with

the same frequency υo as an excitation source. This type of interaction is called an

elastic Rayleigh scattering.

2. A photon with frequency is absorbed by Raman active molecule which at the time of

interaction is in the basic vibrational state. Part of the photon’s energy is transferred to

the Raman active mode with frequency υm and the resulting frequency of scattered

light is reduced to υo−υm. This Raman frequency is called Stokes frequency or just

“Stokes”.

3. A photon with frequency υo is absorbed by a Raman active molecule, which, at the

time of interaction, is already in the excited vibrational state. Excessive energy of

excited Raman active mode is released, molecule returns to the basic vibrational state

and the resulting frequency of scattered light goes up to υo+υm . This Raman frequency

is called Anti Stokes frequency or just “Anti Stokes’’.

The Raman shift does not depend upon the frequency of the incident light but it is

regarded as a characteristic of the substance causing Raman effect. For Stoke’s lines, ∆υ

is positive and for anti stoke’s lines ∆υ is negative.

From fig. 2.18 we can notice that the stokes and anti stokes lines are equally

displaced from the Rayleigh line. This occurs because in either case one vibrational

quantum of energy is gained or lost. Also, note that the anti stokes line is much less

intense than the stokes line. This occurs because only molecules that are vibrationally

excited prior to irradiation can give rise to the anti stokes line. Hence, in Raman

spectroscopy, only the more intense stokes line is normally measured. Infrared absorption

spectroscopy is another similar vibrational technique used to examine molecular structure

but differs from Raman spectroscopy in the manner in which way the molecular


transitions are taking place. For a transition to be Raman active there must be a change in

the polarizability of the molecule during the vibration. This means that the electron cloud

of the molecule must undergo positional change. On the other hand, for an Infrared

detectable transition, the molecule must undergo dipole moment change during vibration.

Homonuclear diatomic molecules such as H2, N2, O2, etc. which do not show infrared

spectra since they do not possess a permanent dipole moment do show Raman spectra

since their vibration is accompanied by a change in polarizability of the molecule. Thus,

Raman spectroscopy permits us to examine the vibrational spectra of compounds that do

not lend themselves to IR absorption spectroscopy.

Raman spectroscopy can be used on liquids, solids and gases making it very

versatile for studying various materials. Because of the distinct spectra that certain

classes of materials give off, due to their structural arrangement, Raman spectroscopy can

be used to determine the composition of unknown substances. This also makes Raman

spectroscopy ideal for qualitative analysis of materials. In Raman spectroscopy no probe

physically touches the material the laser light is the only thing to disturb the sample, this

means that the material is not disturbed by the probe physically touching it and in some

cases is the only way to accurately study a material.

Fig. 2.17 Shows vibrational levels of the material.


Fig. 2.18 Raman spectrum.


A Raman system typically consists of four major components:

1. Excitation source (Laser).

2. Sample illumination system and light collection optics.

3. Wavelength selector (Filter or Spectrometer).

4. Detector (Photodiode array, CCD or PMT).

Fig. 2.19 Schematic diagram of Raman spectrometer. In Raman instrument a

sample is illuminated with a laser beam. Light from the illuminated spot is collected with

a lens and sent through interference filter or spectrometer to obtain Raman spectrum of a

sample. Wavelengths close to the laser line, due to elastic Rayleigh scattering, are filtered

out while the rest of the collected light is dispersed onto a detector. By changing the laser

light you can confirm if a peak is a true Raman peak and not a peak just associated with

the wavelength of the laser light that was used. Spontaneous Raman scattering signal is

very weak because most of the incident photons undergo elastic Rayleigh scattering.

Therefore special measures should be taken to distinguish it from the predominant

Rayleigh scattering. Instruments such as notch filters, tunable filters, laser stop apertures,

double and triple spectrometric systems are used to reduce Rayleigh scattering and obtain

high quality Raman spectra.


In some instruments, sample is placed into the cryostat chamber where the low

temperature is achieved by the use of liquid helium that cooled the cryostat. The cryostat

is kept in vacuum so that laser light suffer no scattering from the particles of the air in the

chamber. Before every measurement the scattered light would have to be aligned in the

spectrometer so that maximum signal would hit the detector. This can be achieved by

moving the sample to different positions and using lens, mirror system. In earlier times

for taking Raman spectrum single point detectors such as photon counting

Photomultiplier Tubes (PMT) was used. However, due to the consumption of very long

time PMT is not preferred because it slow down any research or industrial activity based

on Raman analytical technique. Nowadays, Raman spectroscopy has become even more

accurate and easier due to advancements in optics, laser and computer technology.

Researchers use multi channel detectors like Photo Diode Arrays (PDA) or, more

commonly, a Charge Coupled Devices (CCD) to detect the Raman scattered light.

Charge Coupled Device (CCD) detectors have enormously helped the use of

Raman spectroscopy by allowing scientist to take data quicker and with more precision

that they were able to with the older photomultiplier tubes. The CCD has an array of

detectors that can look at a range of wavelengths at one time greatly reducing the

collection time. Sensitivity and performance of modern CCD detectors are rapidly

improving. In many cases CCD is becoming the detector of choice for Raman

spectroscopy [9−11].

Raman spectroscopy can be used on liquids, solids and gases making it very

versatile for studying various materials. Because of the distinct spectra that certain

classes of materials give off, due to their structural arrangement, Raman spectroscopy can

be used to determine the composition of unknown substances. This also makes Raman

spectroscopy ideal for qualitative analysis of materials. In Raman spectroscopy no probe

physically touches the material the laser light is the only thing to disturb the sample, this

means that the material is not disturbed by the probe physically touching it and in some

cases is the only way to accurately study a material. Surface Enhanced Raman

Spectroscopy (SERS) and Resonance Raman Effect (RRE) are different types of Raman


spectroscopy. The goal of these two processes is to enhance the weak signal of the

Raman spectra. Micro Raman spectroscopy (MRS) is another type of Raman

spectroscopy and this process reduces the spot size of the light source on the sample,

which is helpful if a small area of the sample is to be observed. It is also used to reduce

damage or heating of the sample by the laser light [9−11]. The experimental set up of

Raman Spectrometer is shown in the fig. 2.20.

Specifications:

Least count : 0.3 cm−1

Range : 50 cm−1

to 4000 cm−1

Detector : Charge Coupled Device (CCD)

Light source : Argon laser (10 mW, λ = 488 nm, color−blue, Eg = 2.53 eV) and He−Ne

(5 mW, λ = 632 nm, color red, Eg = 1.95 eV)

Resolution : Lateral resolution of 1micron, an axial resolution of 2 micron and spectral

resolution of the order of 1 cm−1

Filter : Notch or Plasma filter for intensity variation of incident laser light

Object Lens : Highly stable optics with 10X, 50X, 100X objective lens

Dispersive geometry : 600 and 1800 lines/mm gratings

Temperature range : Low temperature attachment (LN2) upto 85 K

Fig. 2.19 Schematic diagram of Raman spectrometer.


Fig. 2.20 Experimental set up of Raman spectrometer.

2.2.8 Gouy Balance Method


Magnetic susceptibility is measured using very sensitive instrument known as a

magnetic susceptibility balance Gouy balance. The balance contains a pair of magnets

mounted at opposite ends of a beam, initially in equilibrium. When a sample is

introduced into the balance a disruption of the magnetic field results. A current through a

coil located between the poles of a second pair of magnets returns the beam to

equilibrium. The current through the coil is measured and transformed into a numerical

reading. Diamagnetic materials are weakly repelled by an external magnetic field,

resulting in a negative reading. Paramagnetic materials are attracted to an external

magnetic field and give a positive reading.


The Gouy balance measures the apparent change in the mass of the sample as it is

repelled or attracted by the region of high magnetic field between the poles [12]. Some

commercially available balances have a port at their base for this application. In use, a

long, cylindrical sample to be tested is suspended from a balance, partially entering

between the poles of a magnet. The sample can be in solid or liquid form, and is often


placed in a cylindrical container such as a test tube. Solid compounds are generally

ground into a fine powder to allow for uniformity amongst the sample [13]. The sample is

suspended between the magnetic poles through an attached thread or string [12]. The

experimental procedure requires two separate reading to be performed. An initial balance

reading is performed on the sample of interest without a magnetic field (ma). A

subsequent balance reading is taken with an applied magnetic field (mb). The difference

between these two readings relates to the magnetic force on the sample (mb−ma) [12].

The apparent change in mass from the two balance readings is a result of

magnetic force on the sample. The magnetic force is applied across the gradient of a

strong and weak magnetic field. A sample with a paramagnetic compound will be pulled

down towards the magnetic field and provide a positive difference in apparent mass

mb−ma. Diamagentic compounds can either exhibit no apparent change in weight or a

negative change as the sample is slightly repelled by the applied magnetic field [14].

With a paramagnetic sample, the magnetic induction is stronger than the applied field and

magnetic susceptibility is positive. A diamagnetic sample has a magnetic induction much

weaker than the applied field, and a respective negative magnetic susceptibility [15].

In a practical device, the whole assembly of balance and magnet is enclosed in a

glass box to ensure that the weight measurement is not affected by air currents. The

sample can also be enclosed in a thermostat in order to make measurements at different

temperatures [16]. Since it requires a large and powerful electromagnet, the Gouy balance

is a stationary instrument permanently set up on a bench [12]. The apparatus is often

placed on a marble balance table to minimize the vibrations and disruption from the

environment [15]. The stationary magnetic of a Gouy balance is often an electromagnet

connected to a power source, since balance recordings with and without the applied

magnetic field is required of the procedure. Experimental set up shown in fig. 2.21.


Fig. 2.21 Experimental set up Gouy balance method.

Specification:

Magnet : 0.4 Tesla

Balance : Mettler (0.05mg)

2.2.9 Vibrating Sample Magnetometer (VSM)


The vibrating sample magnetometer is a simple yet effective technique for

characterizing properties of magnetic materials. Vibrating sample magnetometry (VSM)

is based on Faraday's law which states that an electromagnetic force is generated in a coil

when there is a change in flux linking the coil [17].

The operation of the VSM is fairly simple: a sample is vibrated between a pair of

pick−up coils and a dc magnetic field is applied to the sample (usually in a direction

perpendicular to the coils). The magnetic field magnetises the sample and so the vibrating

magnetic moment produces a flux that changes with time and, consequently, results in an

ac voltage being induced in the detection coils (From Faraday’s Law). The signal from

the coils is detected with a lock in amplifier because it has both a narrow bandwidth (for

a given relative frequency) and a very high gain. The lock−in amplifier gives a dc voltage


output that is proportional to the magnetic moment of the material; thus one may obtain a

measure of sample magnetisation as a function of magnetic field (magnetisation curve).

Fig. 2.22 shows basic principle of VSM.

Fig. 2.22 Basic principle.


Fig. 2.23 shows Layout of vibrating sample magnetometer. The basic

measurement is accomplished by oscillating the sample near a detection (pickup) coil and

synchronously detecting the voltage induced. By using a compact gradiometer pickup

coil configuration, relatively large oscillation amplitude (1−3 mm peak) and a frequency

of 40 Hz, the system is able to resolve magnetization changes of less than 10−6

emu at a

data rate of 1 Hz. The VSM option for the Physical Property Measurement System

(PPMS) consists primarily of a VSM linear motor transport (head) for vibrating the

sample, a coilset puck for detection, electronics for driving the linear motor transport and

detecting the response from the pickup coils, and a copy of the MultiVu software

application for automation and control.

The sample is attached to the end of a sample rod that is driven sinusoidally. The

center of oscillation is positioned at the vertical center of a gradiometer pickup coil. The


precise position and amplitude of oscillation is controlled from the VSM motor module

using an optical linear encoder signal readback from the VSM linear motor transport. The

voltage induced in the pickup coil is amplified and lock in detected in the VSM detection

module. The VSM detection module uses the position encoder signal as a reference for

the synchronous detection. This encoder signal is obtained from the VSM motor module,

which interprets the raw encoder signals from the VSM linear motor transport. The VSM

detection module detects the in phase and quadrature phase signals from the encoder and

from the amplified voltage from the pickup coil. These signals are averaged and sent over

the CAN bus to the VSM application running on the PC.

The system is designed to be user installable and compatible with existing PPMS

systems. Upgrading your current system will therefore be a simple process. Like the other

PPMS applications, the VSM is used only when required, leaving the PPMS to run other

applications as needed. Since the VSM system is a completely self contained

measurement application, other than one of the PPMS Base Systems, there are no other

PPMS applications or options required for its use. Fig. 2.24 shows experimental set up of

14T PPMS−Vibrating Sample Magnetometer.

Fig. 2.23 Layout of vibrating sample magnetometer.


Fig. 2.24 Experimental set up of 14T PPMS−vibrating sample magnetometer.

Specifications:

Temperature range : 2 to 350 K

Magnetic field : 140 kOe

Sensitivity : 10−5

emu

Temperature stability : ~ 10 mK

2.2.10 Thermogravimetry Analysis (TGA)


It is a simple analytical technique that measures the amount and rate of change in

the weight of a material as a function of temperature or time in a controlled atmosphere.

Measurements are used primarily to determine the composition of materials and to

predict their thermal stability at temperatures up to 1000 °C. It is the most widely used

thermal method as shown in fig. 2.25 which can characterize materials that exhibit weight

loss or gain due to decomposition, oxidation, or dehydration. As materials are heated,

they can lose weight from a simple process such as drying, or from chemical reactions

that liberate gases. Some materials can gain weight by reacting with the atmosphere in

the testing environment. Since weight loss and gain are disruptive processes to the sample

material, knowledge of the magnitude and temperature range of those reactions are


necessary in order to design adequate thermal ramps and holds during those critical

reaction periods. Such analysis relies on a high degree of precision in three

measurements: weight, temperature, and temperature change.

A plot of weight change versus temperature is referred to as the

thermogravimetric curve (TGA curve) which helps in revealing the extent of purity of

analytical samples and determining the mode of their transformations within specified

range of temperature. As many weight loss curves look similar, the weight loss curve

may require transformation before results may be interpreted. A derivative weight loss

curve can be used to tell the point at which weight loss is most apparent.

Therefore, TGA curves can provide information about the composition of multi

component systems, thermal stability, oxidative stability of materials, decomposition

kinetics of materials, the effect of reactive or corrosive atmospheres on materials and

moisture content of materials.

Fig. 2.25 Schematic diagram of thermogravimetric analyzer.


The instrument used in thermogravimetry (TGA) is called a thermobalance. It

consists of a sample pan that is supported by a precision balance. That pan resides in a

furnace and is heated or cooled during the experiment. The mass of the sample is


monitored during the experiment and a purge gas controls the sample environment. This

gas may be inert or a reactive gas that flows over the sample to prevent oxidation or other

undesired reactions and exits through an exhaust. The whole arrangement shown in fig.

2.27 with block diagram in fig. 2.26 provides the flexibility necessary for the production

of useful analytical data in the form of TGA curve. Basic components of a typical

thermobalance are listed below:

1. Balance

2. Furnace: heating device

3. Unit for temperature measurement and control (Programmer)

4. Recorder: automatic recording unit for the mass and temperature changes

The basic requirement of an automatic recording balance are includes accuracy,

sensitivity, reproducibility, and capacity. Recording balances are of two types, null point

and deflection type. The null type balance, which is more widely used, incorporates a

sensing element which detects a deviation of the balance beam from its null position. A

sensor detects the deviation and triggers the restoring force to bring the balance beam to

back to the null position. The restoring force is directly proportional to the mass change.

Deflection balance of the beam type involve the conversion of the balance beam

deflection about the fulcrum into a suitable mass change trace by (a) photographic

recoding i.e. change in path of a reflected beam of light available of photographic

recording, (b) recording electrical signals generated by an appropriate displacement

measurement transducer, and (c) using an electrochemical device. The different balances

used in TGA instruments are having measuring range from 0.0001mg to 1g depending on

sample containers used.

The furnace and control system must be designed to produce linear heating at

over the whole working temperature range of the furnace and provision must be made to

maintain any fixed temperature. A wide temperature range generally 150 °C to 2000 °C

of furnaces is used in different instruments manufacturers depending on the models. The

range of furnace basically depends on the types of heating elements are used. In our

instrument, temperature can vary from 25 °C to 900 °C isothermally and the maximum


temperature range is 1000 °C. Sample weight can range from 1 mg to 150 mg but sample

weights of more than 25 mg are preferred and sometimes excellent results are obtained

with 1mg of material.

Temperature measurement are commonly done using thermocouples,

chromal−alumel thermocouple are often used for temperature up to 1100 °C whereas Pt–

Rh thermocouple is employed for temperature up to 1750 °C. Temperature may be

controlled or varied using a program controller with two thermocouple arrangement, the

signal from one actuates the control system whilst the second thermocouple is used to

record the temperature.

Graphic recorders are preferred to meter type recorders. X−Y recorders are

commonly used as they plot weight directly against temperature. The present instrument

facilitate microprocessor controlled operation and digital data acquisition and processing

using personal computer with different types recorder and plotter for better presentation

of data.

The whole of the balance system is housed in a glass to protect it from dust and

provide inert atmosphere. There is a control mechanism to regulate the flow of inert gas

to provide inert atmosphere and water to cool the furnace. The temperature sensor of

furnace is linked to the programme to control heating rates, etc. The balance output and

thermocouple signal may be fed to recorder to record the TGA Curve [18−26].

Fig. 2.26 Block diagram of thermobalance.


Fig. 2.27 Experimental set up of thermogravimetric analysis.

Specifications:

Temperature Range : Ambient to 1000 ºC

Sensitivity : 0.0001 mg

Atmosphere : N2 or Air

Balance Type : Hangdown Pan

Balance capacity : 1300 mg


2.3 References

[1] J. P. Sibilia

A Guide to Materials Characterization and Chemical Analysis, VCH

Publishers (1998).

[2] D. Brondon, W. D. Kaplan

Microstructural Characterization of Materials, John− Wiley and Sons (1999).

[3] L. F. Vassamillet

J. Appl. Phys. 40 (1969) 1637.

[4] B. E. Warren

X−ray Diffraction, Addison−Wesley (1969).

[5] E. W. Nuffield

X−ray Diffraction Methods, Wiley (1966).

[6] B. D. Cullity

Elements of X−ray Diffraction (2nd

Ed.), Addison−Wesley (1978).

[7] C. Kittel

Introduction to Solid State Physics (7th

Ed.), John−Wiley and Sons (1995).

[8] G. R. Chatwal, S. K. Anand

Instrumental methods of chemical analysis, Himalaya Publishing House

(1979).

[9] J. R. Ferraro, K. Nakamoto, C. W. Brown

Introductory Raman spectroscopy, Academic Press (2003).

[10] I. R. Lewis, H. G. M. Edwards

Handbook of Raman Spectroscopy, CRC Press (2001).


[11] E. Smith, G. Dent

Modern Raman Spectroscopy, John Wiley and Sons Ltd. (2005).

[12] A. Saunderson

Physics Education 3 (1968) 272.

[13] F. Brucacher, L. J. Stafford

J. Chem. Educ. 39 (1962) 574.

[14] N. Holzenkaempfer, J. Gipe

Magnetic Properties of Coordination Complexes, UC Davis ChemWiki

[15] S. Liang, B. Harrison, J. Pagotto

Determination of the Impregnant Concentrations on ASC Type Charcoal,

Defence Research Establishment Ottawa (1997).

[16] A. Earnshaw

Introduction to Magnetochemistry. Academic Press. Publisher (1968).

[17] K. H. J. Buschow, F. R. de Boer

Physics of Magnetism and Magnetic Materials. Kluwer Academic/Plenum

Publisher (2003).

[18] T. C. Daniels

Thermal Analysis, John Wiley & Sons, Hanser Publisher, NewYork (1973).

[19] W. W. Wendlandt

Themal Methods of Analysis, Interscience Publishers, New York (1964).

[20] C. Duval

Inorganic Thermogravimetric Analysis, Elsevier Publisher, NewYork (1963).

[21] C. J. Keattc

An Introduction to Thermogravimetry, Dollimore, Heyden & Son Ltd.,

England (1975).


[22] M. E. Brown

Introduction to Thermal Analysis, Kluwer Academic Publisher, London

(2001).

[23] R. A. Meyers

Encyclopedia of Analytical Chemistry, John Wiley & Sons Ltd., Chichester

(2000).

[24] P. J. Haines

Principles of Thermal Analysis & Calorimetry, Royal Society of Chemistry,

Cambridge (2002).

[25] C. M. Earnest

Compostional Analysis by Thermogravimetry, American Society for Testing

and Materials (1988).

[26] P. D. Garn

Thermoanalytical Methods of Investigations, Academic Press Publisher,

NewYork (1965).

basic principle, working and instrumentation of...

Documents