jerzy e.garbarczyk, wojciech wróbel zakład joniki ciała stałego wydział fizyki pw
DESCRIPTION
Transport ładunku elektrycznego w amorficznych, nanokrystalicznych i kompozytowych przewodnikach elektronowych i jonowych. Jerzy E.Garbarczyk, Wojciech Wróbel Zakład Joniki Ciała Stałego Wydział Fizyki PW. Motywacja. Cel poznawczy - PowerPoint PPT PresentationTRANSCRIPT
Sympozjum Wydziału Fizyki 17 kwietnia 2008
Transport ładunku elektrycznego w amorficznych, nanokrystalicznych
i kompozytowych przewodnikach elektronowych i jonowych
Jerzy E.Garbarczyk, Wojciech Wróbel
Zakład Joniki Ciała Stałego
Wydział Fizyki PW
Motywacja
Cel poznawczyBadanie transportu ładunku elektrycznego w mało poznanych formach fazy skondensowanej
Cel aplikacyjnyZastosowania w urządzeniach do konwersji i magazynowania energii (baterie litowo-jonowe, ogniwa paliwowe, sensory gazowe, superkondensatory)
Sympozjum Wydziału Fizyki 17 kwietnia 2008
Prezentacje
Jerzy E.Garbarczyk
„Nowe nanomateriały i kompozyty oparte na szklistych przewodnikach elektronowych i jonowych”
Wojciech Wróbel
„Korelacja między elektrycznymi i mechanicznymi właściwościami cieczy szkłotwórczych”
Sympozjum Wydziału Fizyki 17 kwietnia 2008
Sympozjum Wydziału Fizyki 17 kwietnia 2008
Novel nanomaterials and composites based on electronic and ionic conductive glasses
Outline
• Advantages and disadvantages of ionic and electronic conductive
glasses
• Novel nanomaterials based on lithium-vanadate-phosphate (LVP)
glasses
• Novel nanomaterials based on lithium-iron-phosphate (LFP)
glasses
• Novel composites based on ionically conductive glasses
• Summary
Advantages and disadvantages of conductive glasses
Advantages simple processing possibility of forming various shapes isotropy and homogeneity absence of grain boundaries high ionic conductivity at room temperature
(up to 10-2 S/cm for AgI – based conducting glasses) high electronic conductivity at above 300ºC (up to 10-3 S/cm for vanadia – rich glasses)
inherent ability to nanocrystallization (this study) possibility of considerable modification of the composition and electrical properties
Example: vanadia-based glasses
V2O5 – main glass former, source of electronic conduction via V4+ → V5+ hopping of small polarons
P2O5 – supporting glass formerLi2O – glass modifier, source of mobile Li+ ionsAg2O – glass modifier, source of mobile Ag+ ionsAgI – dopant, main source of mobile Ag+ ions
Mixed ionic-electronic conductivity in systems: Li2O - V2O5 - P2O5 (Li+/e-)AgI - Ag2O - V2O5 - P2O5 (Ag+/e-)
Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses
or
Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses
or
Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses
or
Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses
or
Model of the electrical charge transport
in Li2O-V2O5-P2O5 glasses
or
Model of the electrical charge transport
in Li2O-V2O5-P2O5 glasses
or
Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses
or
or
Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses
Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses
or
Isotherms of the total electrical conductivity in Li2O-V2O5-P2O5 glasses
V2O5-rich glasses
ionic
electronic
mixed
P.Jozwiak, J.Garbarczyk, Solid State Ionics 176 (2005) 2163
H.Takahashi, T.Karasawa, T.Sakuma,J.E.Garbarczyk, ICPSSI-2, Yokohama, 2007
Total electrical conductivity at 100°C vs. composition in AgI-Ag2O-V2O5-P2O5 glasses
J.E.Garbarczyk, P.Machowski et al.Mol.Phys.Rep. 35 (2003) 139.
electronic
ionic
Total electrical conductivity at 100°C vs. composition in AgI-Ag2O-V2O5-P2O5 glasses
electronic
ionic
electronic
ionic
J.E.Garbarczyk, P.Machowski et al.Mol.Phys.Rep. 35 (2003) 139.
Advantages and disadvantages of conductive glasses (cont.)
Disadvantages
metastability composition and structure less known than those of the crystalline
materials low glass transition temperature of the best ion conductive glasses
(for AgI-doped glasses 60°C < Tg < 100°C) low fracture toughness moderate electronic conductivity at 20°C of glassy cathode materials
Aims of our studies
preparation of new nanomaterials derived from conductive glasses exhibiting better electrical properties and thermal stability than the initial glasses
preparation of new glassy-crystalline composites exhibiting improved mechanical properties compared to the glasses
Novel nanomaterials based on lithium-vanadate-phosphate (LVP) glasses
It is known that nanostructured materials exhibit attractive properties, often dramatically different than those of the crystalline or amorphous counterparts.
Effect of nanocrystallization on ionic conductivity St. Adams, K.Hariharan, J.Maier, Solid State Ionics 86-88 (1996) 503.
AgI-rich glasses of the system AgI-Ag2O-MxOy
Effect of nanocrystallization on electronic and mixed conductivity
J.E.Garbarczyk, P.Jozwiak et al. Solid State Ionics 175 (2004) 691.
V2O5-rich glasses of the system Li2O-V2O5-P2O5
a) 15Li2O·70V2O5· 15P2O5
b) 90V2O5· 10P2O5
DSC
Nanocrystallization of the90V2O5∙10P2O5 glass
SEM picture of a 90V2O5∙10P2O5 sample
after nanocrystallization at Tc ≈ 340°C
SEM picture of a 90V2O5∙10P2O5 sample
after nanocrystallization at Tc ≈ 340°C
20 nm
visible nanocrystallites of V2O5 covered by a glassy phase
SEM picture and XRD pattern of a 90V2O5∙10P2O5
sample after massive crystallization at 540°C
● - orthorhombic V2O5
SEM picture of a 90V2O5∙10P2O5 sample after massive crystallization at 540oC (another fragment)
orthorhombic V2O5 crystallites
Discussion of the results on vanadia-based nanomaterials
Mott theory of electron hoppingMott theory of electron hopping in disordered systems in disordered systems
0 expe ee
ET
T kT
R – average distance between hopping centers
C – fraction of hopping sites occupied by electrons
N – concentration of hopping centres – inverse localization length of the electron
wave function
rp – radius of a small polaron
2e mR
for T > / 2
– Debye temperature
2
0
1exp 2e e
e C CR
kR
1 3R N
4+
4+ 5+
V
V + VC
0 1
pe
rE W
R
Discussion of the results on vanadia-based nanomaterials
Samples after nanocrystallization
V2O5
20 nm
Discussion of the results on vanadia-based nanomaterials
Samples after nanocrystallization
V2O5
20 nm
higher concentration of
V4+ -V+5 pairs
Discussion of the results on vanadia-based nanomaterials
Samples after nanocrystallization
„Easy conduction paths” – interface regions between nanocrystallites and glassy phase.Higher concentration of V4+-V5+ pairs in these regions than inside grains.
V2O5
20 nm
high concentration of
V4+ -V+5 pairs
easy conduction path
–
+
Discussion of the results (cont.) Sample after massive crystallization
There is no intermediate glassy phase. The electrical transport between grains is partly blocked by the presence of grain boundaries.
Novel nanomaterials based on lithium-iron-phosphate (LFP) glasses
Crystalline lithium-iron-phosphates (olivines)
Nanocrystallization of glassy samples - SEM
Cooperation with Prof. Christian Julien, Univ. P.et M.Curie, Paris, France(local structure)
A.Ait Salah, P.Jozwiak, J.Garbarczyk, Ch.Julien et al.Journal of Power Sources 140 (2005) 370.
Związki interkalowane - przykłady
Oliwiny i związki pokrewne
Crystalline lithium-iron-phosphates
Crystalline olivine-type phases - LiFePO4 and FePO4 as well as LixFePO4 solid solutions - are under intensive studies worldwide as the most competitive cathode materials for Li-ion rechargeable batteries.
These cathode materials are: • highly stable (thermally and electrochemically),• inexpensive,• environment – friendly.
Furthermore they exhibit:• high specific capacity (170 mAh/g),• high discharge voltage (3.5 V vs. Li).
Crystalline lithium-iron-phosphates
Crystalline olivine-type phases - LiFePO4 and FePO4 as well as LixFePO4 solid solutions - are under intensive studies worldwide as the most competitive cathode materials for Li-ion rechargeable batteries.
These cathode materials are: • highly stable (thermally and electrochemically),• inexpensive,• environment – friendly.
Furthermore they exhibit:• high specific capacity (170 mAh/g),• high discharge voltage (3.5 V vs. Li).
Unfortunately they have one serious deficiency – very low electrical conductivity - ca. 10-10 S·cm‑1 at 25°C.
Crystalline olivines (cont.)
Many efforts have been undertaken to improve their electrical properties by:
• introduction of carbon additives, • doping with supervalent cations,• various synthesis routes.
Our alternative approach – nanocrystallization of glassy analogs of olivines:
• step 1: preparation of vitreous analogs of these materials,• step 2: turning these glasses into nanomaterials by an
appropriate thermal treatment.
Electrical properties after partial nanocrystallization (sample of x = 0)
SEM picture after partial nanocrystallization for sample of x = 0
Electrical properties after partial nanocrystallization (sample of x = 0.4)
σt(530°C)=1.1∙10-2 S/cm
σt(50°C)= 1.8∙10-8 S/cm
σt(50°C)=7.6∙10-8 S/cm
≈ 4 times
SEM micrograph after crystallization for sample of x = 0.4
SEM micrograph after crystallization for sample of x = 0.4
Novel composites based on ionically conductive glasses
Motivation
Ag+ - ion conductive glasses exhibit high electrical conductivity (up to 10-2 S·cm-1 at 25°C), but some of their mechanical properties may cause problems with samples machining (e.g. cutting and polishing) and limit eventual prospective applications.
In order to minimize this drawback we propose new composites based on silver-ion conductive glasses.
Novel composites based on ionically conductive glasses (cont.)
Glassy components:
AgI-Ag2O-B2O3
AgI-Ag2O-P2O5
AgI-Ag2O-V2O5
Ceramic powder components: Diamond (1-2 µm)
-Al2O3 (2 µm)
ZrO2 (1 and/or 10 µm)
Composites prepared in 50 - 50 % vol fractions
B2O3, P2O5, V2O5 – glass formersAg2O – glass modifierAgI – dopant
High-pressure route of preparation of the composites
Facility at the Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw
com pactedglass pow dercom pactedceram ic pow der
graphiteheater
High-pressure route of preparation of the composites (cont.)
100-200°C
com pactedglass pow dercom pactedceram ic pow der
graphiteheater
Pressure
Pressure
Temperature
100-250°C
3-8 GPa
SEM and XRD studies
Obrazek SEM(fosforanowe z diamentem, boranowe z alumina)
Glass: 40AgI·30Ag2O·30P2O5
Diamond powder (1-2 m)Synthesis: p = 3 GPa, T = 250°C
as-prepared after annealing at 200°C
M.Zgirski, J.Garbarczyk et al., Solid State Ionics, 176 (2005) 2141
SEM studies (cont.)
50AgI·33Ag2O·17B2O3 : -Al2O3 (2 m) - a phase view
Al2O3
Al2O3
Glass
SEM studies (cont.)
55AgI·30Ag2O·15B2O3 : ZrO2 (1 m) - a phase view
ZrO2
Electrical properties of compositesabove room temperature
40AgI·30Ag2O·30P2O5 : diamond
200=1.6·10-2 S·cm-1
27=1·10-4 S·cm-1
E=0.34 eV
E=0.54 eV
Tg
glass
4 6 8 10 12-15
-10
-5
0
Glass50AgI·33Ag
2O·17B
2O
3
glass
E = 0.30 eV
E = 0.30 eV
Composite 50AgI·33Ag
2O·17B
2O
3 + Al
2O
3 (2 m)
Synthesis: T = 100°C, p = 7.7 GPa
log(T
/ S
·cm
-1K
)
1000 K / T
composite
40 0 -40 -80 -120 -160
t / °C
Electrical conductivity of compositesat low temperatures
M.Foltyn, M.Wasiucionek, J.E.Garbarczyk et al.., Solid State Ionics, 179 (2008) 38
Mechanical properties - Vickers microhardness
40 45 50 55 60
100
150
200
250
mic
roha
rdne
ss [k
G·m
m-2]
x [%mol]
xAgI·(100-x)(0.67Ag2O·0.33B2O3)
composites (with -Al2O3)
glasses
Electrical properties of composites (cont.)
Lower specific conductivity of the composites can be compensated by a possibility of preparing thinner samples.
Mechanically sound membranes of ca 100 m thickness can be fabricated.
sheet of paper - edge
composite 1. (ca 100 m)
composite 2. (ca 300 m)
Summary
Conductive glasses can be promising starting materials to prepare attractive composites and nanostructured materials.
The annealing of the V2O5 – rich glasses (LVP) to Tc leads to their nanocrystallization.
The resulting nanomaterials exhibit much higher electronic conductivity (10-1 S/cm at 300ºC), lower activation energy and better thermal stability than the initial glasses.
Summary (cont.)
Electrical properties of lithium-iron-phosphate (LFP) glasses are similar to crystalline olivines.
It was found that thermal nanocrystallization of LFP glasses leads to the conductivity enhancement,
Summary (cont.)
Electrical properties of lithium-iron-phosphate (LFP) glasses are similar to crystalline olivines.
It was found that thermal nanocrystallization of LFP glasses leads to the conductivity enhancement,
...therefore it seems to be a promising way for electrical conductivity improvement of amorphous lithium-iron-phosphates.
A prospective high-pressure method was used to produce silver ion conductive composites based on AgI – doped glasses with good electrical and mechanical properties.
Zespół badawczy
Marek Wasiucionek
Paweł Jóźwiak
Jan L.Nowiński
Marek Foltyn
Irena Gorzkowska – Wydział Chemiczny PW
Bogdan Pałosz – Unipress (IWC PAN)
Stanisław Gierlotka – Unipress (IWC PAN)
R. Bacewicz, M. Wasiucionek, A. Twaróg, J. Filipowicz, P. Jóźwiak, J.E. Garbarczyk, J. Mat. Sci. 40 (2005) 4267-4270.
Electrical properties of composites above room temperature
40AgI·40Ag2O·20B2O3 : -Al2O3
M.Foltyn, M.Wasiucionek, J.Garbarczyk et al.J.Power Sources 173 (2007) 795
=1.6·10-2
=2.5·10-3