Ag 5 Te 2 Cl 1x Br x (x  0  0.65) and Ag 5 Te 2y S y Cl (y  0  0.3): Variation of Physical Properties in Silver(I) Chalcogenide Halides Tom Nilges* and Stefan Lange Münster/Deutschland, Institut für Anorganische und Analytische Chemie der Universität Received June 6th, 2005. Abstract. The structures, thermal and physical properties of ion conducting polymorphic Ag 5 Te 2 Cl 1-x Br x and Ag 5 Te 2-y S y Cl have been investigated. A maximum substitution degree of x = 0.65 and y = 0.3 was derived from X-ray powder diffraction. Mixtures of silver halides, silver chalcogenides and Ag 3 TeBr were observed for higher substitution degrees. Both silver chalcogenide halide systems show a Vegard type behaviour. Single crystal structure determina- tions of selected materials were performed at different temperatures to analyse the silver distribution in the tetragonal high temperature - and the monoclinic room temperature β-phases. After non-har- monic refinement of the silver positions detailed joint probability density function analysis (jpdf) and determination of one particle potentials (opp) were carried out to investigate the diffusion path- ways and bottlenecks of ion transport for those materials. A prefer- red anisotropic ion transport along the 1  [Ag] diffusion pathways for the - and 1D zig-zag diffusion pathways for the β-phases were found. -β and β-γ phase transitions were determined by DSC and DTA methods and conductivities were measured using temperature dependent impedance spectroscopy. The substitution of tellurium Introduction The optimisation of physical properties like enhancement of ion conductivity in combination with high light and moisture stability is a field of scientific research aiming to obtain new materials for electronic devices and sensors. The determination of structure property relations plays a key role for a successful optimisation process. An extensive summary in the field of silver ion conducting materials has been reported by Funke [1] and ongoing scientific progress can be found in the literature [2]. Today silver chalcogenides are of special interest due to their colossal magneto resist- ance [3-5]. Materials like Ag 5-x Te 3 [6] show the potential of the silver chalcogenides as candidates with ion dynamic in the solid state. Interesting physical properties such as high ion conductivities and their optimisation by anion sub- * Dr. Tom Nilges Institut für Anorganische und Analytische Chemie Corrensstraße 30 48149 Münster Tel.: (+49)-251-83-36645 Fax: (+49)-251-83-36002 E-mail: nilges@uni-muenster.de Supporting information for this article is available on the WWW under http://www.wiley-vch.de/home/zaac or from the author 3002  2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim DOI: 10.1002/zaac.200500261 Z. Anorg. Allg. Chem. 2005, 631, 3002-3012 by sulphur lowered the -β phase transition from 334 K (Ag 5 Te 2 Cl) to 270 K (Ag 5 Te 1.8 S 0.2 Cl) while the opposite trend was found for the Ag 5 Te 2 Cl 1-x Br x phases. The -β phase transition of Ag 5 Te 2 Cl 0.35 Br 0.65 at 343 K represents the highest transition obser- ved for the silver chalcogenide halides under discussion. Total con- ductivities of approx. 1 Ω -1 cm -1 (-Ag 5 Te 2 Cl 0.5 Br 0.5 ) and 0.24 Ω -1 cm -1 (-Ag 5 Te 1.8 S 0.2 Cl) at 473 K were found being slightly higher (Br) and lower (S) than the conductivity observed for -Ag 5 Te 2 Cl. A conductivity jump of more than two orders of magnitude, related to the -β phase transitions, within the tempe- rature range from 270 to 343 K is adjustable by simple variation of the composition and is therefore an extraordinary feature of these materials. The total conductivity is linearly correlated to the vo- lume of the anion substructure and can be varied within more than half an order of magnitude. Keywords: Silver chalcogenide halides; Ion conductors; Non- harmonic refinements; Joint probability density functions; One particle potentials stitution were reported for Ag 3 SX (X = I, Br, Cl) [7-9]. Substitution of the halide resulted in different phase tran- sition temperatures related to the degree of substitution and the type of halide [10, 11]. Ternary halides like β-Ag 2 ZnI 4 or β-Ag 2 CdI 4 [12] show approximately a 12-fold increase in ionic conductivity on heating, undergoing the phase tran- sitions from the ordered wurtzite and zincblende structure type to the disordered high temperature counterparts. Recently we started to examine polymorphic Ag 5 Te 2 Cl which shows high ion mobility, especially in its high tem- perature phase. Based on the structures and physical properties of the three polymorphs -Ag 5 Te 2 Cl [13], stable from 790 to 334 K, β-Ag 5 Te 2 Cl (334 to 241 K) [13, 14] and γ-Ag 5 Te 2 Cl (< 241 K) [15] we were able to vary the thermal and electrical properties by partial substitution of tellurium by selenium [16]. The transition temperatures of the poly- morphs could be significantly lowered by this substitution while preserving the structure types defining the Ag 5 Te 2 Cl structure family. Materials of the -Ag 5 Te 2 Cl structure type show high conductivities (e.g. σ = 5.1 · 10 -2 Ω -1 cm -1 at 314 K for Ag 5 Te 1.6 Se 0.4 Cl). This structure type could be stabilized down to 239 K in Ag 5 Te 1.3 Se 0.7 Cl. The effect of chalcogen substitution in the non-mobile anion substruc- ture illustrates the optimisation potential by chemical modi- fication of the materials. Encouraged by the successful sub- stitution of tellurium by selenium we tried to prepare mixed