Variation of physical properties of silver(I) chalcogenide halides by

modification of the anion substructure

Stefan LangeInstitute of Inorganic Chemistry

University of Regensburg

NRW Graduate School of Chemistry, 25.–27.08.2004

• Ag5Te2Cl is a trimorphic compound:

-Ag5Te2Cl -Ag5Te2Cl -Ag5Te2Cl

monoclinic (P 21/c) monoclinic (P 21/n) tetragonal (I 4/mcm)

a=1935.9(1) pm a=1385.2(3) pm a=974.9(2) pm

b=771.3(1) pm b=766.3(2) pm

c=1953.3(1) pm c=1366.1(3) pm c=783.6(2) pm

Z=16 Z=8 Z=4

=90.6(1)° =90.09(1)°

(193 K) (298 K, powder XRD) (363 K, powder XRD)

R. Blachnik, H. A. Dreisbach, J. Solid State Chem., (1985), 60, 115.

Th. Doert, E. Rönsch, F. Schnieders, P. Böttcher, Z. Anorg. Allg. Chem., (2000), 626, 89-93.

T. Nilges, S. Nilges, A. Pfitzner, Th. Doert, P. Böttcher, Chem. Mater., (2004), 16, 806-812.

Ag5Te2Cl: Structures

334 K241 K

T. Nilges, S. Nilges, A. Pfitzner, Th. Doert, P. Böttcher, Chem. Mater., (2004), 16, 806-812.

Anion substructure:

• minor distortion of the anion sublattice upon phase transition --• description as alternating nets in projection along selected crystallographic axes: • 44 for Cl and 32434 for Te

Ag5Te2Cl: Structures

ab

a

ca

c

TeCl

Anion substructure:

Ag5Te2Cl: Structures

ab

a

ca

c

TeCl

T. Nilges, S. Nilges, A. Pfitzner, Th. Doert, P. Böttcher, Chem. Mater., (2004), 16, 806-812.

• minor distortion of the anion sublattice upon phase transition --• description as alternating nets in projection along selected crystallographic axes: • 44 for Cl and 32434 for Te

Anion substructure:

ab

a

ca

c

TeCl

Ag5Te2Cl: Structures

Ag5Te2Cl: Structures

Ag5Q2X: Ag-coordination4 different types of silver coordination in the -phase:

• Aga{1,2,3,4,5,8}: distorted tetrahedral coordination by 3 Te + 1 Cl• Aga{6,7}: distorted tetrahedral coordination by 2 Te + 2 Cl• Agb1: almost regular tetrahedral coordination by 4 Te• Agb2: trigonal-planar coordination by 3 Te

[2+2] and [3+1] coordination [3+1] coordination

Aga5

Aga8

Aga4

Aga1

TeClAg

Aga2 Aga3

Aga6 Aga7

Agb1

Agb2

[3] and [4] Te-coordination

4 different types of silver coordination in the -phase:• Aga{1,2,3,4,5,8}: distorted tetrahedral coordination by 3 Te + 1 Cl • Aga{6,7}: distorted tetrahedral coordination by 2 Te + 2 Cl• Agb1: almost regular tetrahedral coordination by 4 Te• Agb2: trigonal-planar coordination by 3 Te

Ag5Q2X: Ag-coordination

Substitution of the anion sublattice

Ag5Te2Cl

Substitution of the anion sublattice

Ag5Te2ClTe S Te Se

Ag5Te2-ySyCl

Ag5Te2-zSezCl

y = 0 – 0.3 z = 0 – 0.7

T. Nilges, C. Dreher, A. Hezinger, Solid State Sci., in press.

Substitution of the anion sublattice

Ag5Te2ClTe S Cl Br Te Se

Ag5Te2-ySyCl Ag5Te2Cl1-xBrx

Ag5Te2-zSezCl

y = 0 – 0.3 x = 0 – 0.65z = 0 – 0.7

T. Nilges, C. Dreher, A. Hezinger, Solid State Sci., in press

Ag5Te2Cl1-xBrx: DSC

150 200 250 300 334 350

T / K

x=0.1

x=0.7

x=0.6

x=0.5

x=0.4

x=0.3

x=0.2

x=0endo

333.6 K

334.9 K

336.2 K

338.1 K

340.2 K

341.2 K

343.3 K

344.0 K

243.7 K

215.8 K

187.0 K

150.5 K

Ag5Te2-ySyCl: DSC

180 200 220 240 260 280 300 320 340 360

T / K

y=0.1

y=0.2

y=0

endo

333.6 K

306.9 K

270.2 K

243.7 K

Ag5Q2X: phase diagrams

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7

120

150

180

210

240

270

300

330

660

690

720

750

780

x(Br) in Ag5Te

2Cl

1-xBr

x

T /

K

Ag5Te

2Cl Ag

5Te

2Cl

0.3Br

0.7

-Ag5Te

2Cl type

-Ag5Te

2Cl type

-Ag5Te

2Cl type

0,0 0,1 0,2 0,3

120

150

180

210

240

270

300

330

660

690

720

750

780

Ag5Te

2Cl y(S) in Ag

5Te

2-yS

yCl

T /

KAg

5Te

1.7S

0.3Cl

-Ag5Te

2Cl type

-Ag5Te

2Cl type

-Ag5Te

2Cl type

Ag5Te2Cl1-xBrx Ag5Te2-ySyCl

Ag5Q2X: cell volumespowder XRD at room temperature and 363 K

linear increase of lattice constants and cell volumes with increasing degree of substitution for both Ag5Te2Cl1-xBrx and Ag5Te2-ySyCl

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7180

181

182

183

184

185

186

187

188

189

190

RT 363 K

VF

U /

(1

00

pm

)3

x in Ag5Te

2Cl

1-xBr

x

0,0 0,1 0,2 0,3180

181

182

183

184

185

186

187

188

189

190

VF

U /

(100

pm

)3

y in Ag5Te

2-yS

yCl

363 K RT

Ag5Te2Cl1-xBrx Ag5Te2-ySyCl

error bars are drawn for +/- 3

-type

type

-type

-type

impedance spectroscopy from 30 °C – 200 °C, = 100 mHz – 4 MHz• slight increase of conductivity and activation energies with increasing x (Cl-Br-substitution)• comparable conductivities and activation energies for Te-S-substitution; stabilization of the

HT--phase at room temperature

Ag5Q2X: electric conductivity

2,0 2,2 2,4 2,6 2,8 3,0 3,2-4,0

-3,5

-3,0

-2,5

-2,0

-1,5

-1,0

-0,5

0,0

0,5

log

(

/

cm

-1 )

103 T-1 / K-1

Ag5Te

2Cl

0.5Br

0.5

Ag5Te

2Cl

0.8Br

0.2

Ag5Te

2Cl

Ag5Te

1.8S

0.2Cl

x(Br)/y(S) Ea () Ea ()

0 0.22 eV 0.50 eV

x(Br)=0.2 0.24 eV 0.51 eV

x(Br)=0.5 0.25 eV 0.51 eV

y(S)=0.2 0.21 eV -

Jpdf and opp-analysis of single crystal X-ray data• calculated activation barriers show same magnitude and trend as results

from impedance spectroscopy

-Ag5Te2Cl1-xBrx: diffusion pathways

Aga6 Aga7

Agb2

Aga1 Aga8AgTeCl/Br

Ag5Te2Clisovalue 0.999

Ag5Te2Cl0.5Br0.5

isovalue 0.999

• Dr. T. Nilges

• Prof. Dr. A. Pfitzner• Prof. Dr. R. Pöttgen (University of Münster)

• Dr. M. Zabel, Dr. M. Andratschke, S. Stempfhuber• D. Feil

• all other members of the Pfitzner workgroup

Acknowledgements