The thermoelectric properties of n-type InxPb1−xTe1−yIy (with x = 0.005, 0.01, 0.015; y = 0.001, 0.002, 0.004, 0.006) were investigated at elevated temperatures up to 655 K. This co-doping significantly affected the Seebeck coefficient and electrical conductivity of all samples within the measured temperature regime except for the sample with the largest concentration of In, wherein the effects of I-doping are comparatively minor. For a given concentration of In, the sample with the largest amount of iodine possesses the highest electrical conductivity, which is consistent within all three sets of samples in our present study. Thermal conductivity values are generally lower than those of undoped PbTe. An increasing iodine concentration at fixed In content was found to gradually increase the dimensionless figure-of-merit, ZT, an effect most significantly observed when x = 0.01.

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We have synthesized Tl2ZrTe3 at elevated temperatures starting from the elements. Tl2ZrTe3 adopts a cubic structure, space group P213 with a unit cell parameter of a = 19.118(1) Å (Z = 36). All Tl and Zr atoms are octahedrally (distorted) coordinated by Te atoms. One out of 11 crystallographically distinct Te atoms in the structure is not connected to any Zr atoms, but is surrounded by six Tl atoms in the form of a severely distorted octahedron. Because of the absence of any significant homonuclear interactions, all atoms are in their most common oxidation states, namely, Tl+, Zr4+, and Te2–. Electronic structure calculations and physical property measurements reveal the semiconducting characteristics of the compound. The structure and thermoelectric properties of Tl2ZrTe3 and Tl2SnTe3 are compared in the present work. The dimensionless figure of merit, ZT, was found to be 0.18 for Tl2ZrTe3 at 420 K and 0.31 for Tl2SnTe3 at 500 K, with both materials exhibiting very low thermal conductivity. Tl2ZrTe3 decomposes irreversibly around 450 K in open systems under inert gas atmosphere, while it remains stable up to its incongruent melting point at 835 K in closed silica tubes.

The antimonide Hf 3 Cu 2 Ge 3.58 Sb 1.42 was obtained via a two-step synthesis: arc-melting of hafnium, copper, and germanium under argon was followed by a reaction of the thus obtained ingot with antimony under a vacuum in a silica ampule. This compound adopts a new structure type, space group P4/nmm, with lattice dimensions of a= 3.8023(6) A ˚, c=24.575(4) A ˚, V=355.29(10) A ˚3. The structure of Hf 3 Cu 2 Ge 3.58 Sb 1.42 comprises puckered double layers of the Hf and Ge/Sb atoms as well as ¥ 2 [Cu] and ¥ 2 [Ge/Sb] planar square nets, representing a new intergrowth structure of ZrSiS-and NdTe 3 -like slabs. The ¥ 2 [Ge/Sb] square nets are composed of one disordered site that is statistically mixed occupied by 88% Ge and 12% Sb atoms. Electronic structure calculations predicted metallic properties, subsequently confirmed by an Seebeck and an electrical resistivity measurement.

Structural, Thermal, and Physical Properties of the Thallium Zirconium TellurideTl2ZrTe3. -The title compound is prepared from the elements (1073 K, 100 h) and characterized by single crystal XRD, electrical and thermal conductivity measurements, and extended Hueckel tight binding electronic structure calculations. Tl2ZrTe3 crystallizes in the cubic space group P213 with Z = 36. The structure contains a three-dimensional network of edge-sharing distorted ZrTe 6 octahedra. One of the Te sites is not in contact with any of the Zr atoms in the structure, but centers a TeTl6 octahedron. The structure and thermoelectric properties of the title compound and Tl2SnTe3 are compared. The figure of merit is 0.18 for the title compound at 420 K and 0.31 for Tl2SnTe3 at 500 K. Tl2ZrTe3 decomposes irreversibly around 450 K in an open system, while it remains stable up to 835 K in closed silica tubes. -(SANKAR, C. R.; GUCH, M.; ASSOUD, A.; KLEINKE*, H.; Chem. Mater. 23 (2011) 17, 3886-3891, http://dx.doi.org/10.1021/cm200994t ; Dep. Chem., Univ. Waterloo, Waterloo, Ont. N2L 3G1, Can.; Eng.) -W. Pewestorf 45-003