Silver Indium Telluride Semiconductors and Their Solid Solutions with Cadmium Indium Telluride: Structure and Physical Properties

Abstract

Ag0.8In2.4Te4 (= AgIn3Te5) and Ag0.5In2.5Te4 (= AgIn5Te8) form solid solutions with CdIn2Te4, which are interesting as materials for photovoltaics or with respect to their thermoelectric properties. The corresponding crystal structures are related to the chalcopyrite type. Rietveld refinements of high-resolution synchrotron powder diffraction data measured at K-absorption edges of Cd, Ag, In, and Te and electron diffraction reveal the symmetry as well as the element and vacancy distribution in Ag0.8In2.4Te4 (= AgIn3Te5)/Ag0.5In2.5Te4 (= AgIn5Te8) mixed crystals such as Ag0.25Cd0.5In2.25Te4 and Ag0.2Cd0.75In2.1Te4. All compounds of the solid solution series (CdIn2Te4)x(Ag0.5In2.5Te4)1-x exhibit the HgCu2I4 structure type (space group I4̅2m) with completely ordered vacancies but disordered cations. The uniform cation distribution and thus the local charge balance are comparable to that of CdIn2Te4. In contrast, Ag0.8In2.4Te4 (= AgIn3Te5) crystallizes in the space group P4̅2c with disordered cations and partially ordered vacancies. This is corroborated by bond-valence sum calculations and the fact that there is a Vegard-like behavior for compounds with 0.5 < x in the pseudobinary system (CdIn2Te4)x(Ag0.8In2.4Te4)1-x. Owing to the different structures, there is no complete solid solution series between CdIn2Te4 and AgIn3Te5. All compounds in this work are n-type semiconductors with a low electrical conductivity (∼1 S/m) and rather high absolute Seebeck coefficients (up to -750 μV/mK; 225 °C). Electrical band gaps (Eg) determined from the Seebeck coefficients as well as (more reliably) from the electrical conductivity range between 0.19 and 1.13 eV.

Negative thermal expansion and electronic structure variation of chalcopyrite type LiGaTe2

“…[1][2][3][4][5][6][7][8][9][10][11][12] Because of specic features of metal-tellurium chemical bonds, tellurides possess narrow-bandgap semiconductor or metallic properties. 1,2,[6][7][8]11,12 Due to their low-wavenumber phonon spectrum, semiconductor tellurides are transparent in the mid-IR range and they can be used as optical window materials. However, the number of known noncentrosymmetric tellurides is not big and, only for several crystals, the linear and nonlinear properties are obtained.…”

Data-driven exploration of new pressure-induced superconductivity in PbBi2Te4

“…AgIn5Se8 is also expected as a candidate for a superior thermoelectric material [15,17]. Moreover, since AgIn5Se8 equips high DOS near valence band edges, it could be expected the appearance of superconductivity by band-structure engineering using high pressure technique.…”

The use of anomalous x-ray diffraction as a tool for the analysis of compound semiconductors

“…This reduces the number of independent occupation factors for any given atomic side, thus simplifying the analysis. Solid solutions of silver indium telluride semiconductors with cadmium indium telluride have been analyzed by joint Rietveld refinement making use of anomalous scattering of all four elements involved [38,39]. The K-edges of these species lie in the range of 25 -32 keV.…”

“…In contrast for example, silver indium telluride [38,39] also has a crystal structure derived from the sphalerite type by cation ordering. The disordered form has the same symmetry as disordered CZTS, 𝐼4 ̅ 2𝑚 with a doubling of the c-lattice parameter compared to the cubic unit cell of sphalerite.…”