A high-pressure route to thermoelectrics with low thermal conductivity: The solid solution series AgInxSb1−xTe2 (x=0.1–0.6)

Abstract Metastable rocksalt-type phases of the solid solution series AgIn x Sb 1− x Te 2 ( x =0.1, 0.2, 0.4, 0.5 and 0.6) were prepared by high-pressure synthesis at 2.5 GPa and 400 °C. In these structures, the coordination number of In 3+ is six, in contrast to chalcopyrite ambient-pressure AgInTe 2 with fourfold In 3+ coordination. Transmission electron microscopy shows that real-structure phenomena and a certain degree of short-range order are present, yet not very pronounced. All three cations are statistically disordered. The high degree of disorder is probably the reason why AgIn x Sb 1− x Te 2 samples with 0.4 x κ κ ph ∼0.3 W/K m at room temperature. These are lower than those of other rocksalt-type tellurides at room temperature; e.g. the well-known thermoelectric AgSbTe 2 ( κ ∼0.6 W/K m). The highest ZT value (0.15 at 300 K) is observed for AgIn 0.5 Sb 0.5 Te 2 , mainly due to its high Seebeck coefficient of 160 µV/K. Temperature-dependent X-ray powder patterns indicate that the solid solutions are metastable at ambient pressure. At 150 °C, the quaternary compounds decompose into chalcopyrite-type AgInTe 2 and rocksalt-type AgSbTe 2 .