Synthesis, Structural, and Morphological Studies of the Thermoelectric Semiconductor AgSb1-x Cd x Te2.

The compound AgSbTe2 was synthesized by the high-temperature solid-state route using two methods: (i) continuous slow cooling and (ii) annealing at an intermediate temperature followed by quenching. Powder X-ray diffraction confirmed the principal phase with an fcc (Fm3̅m) crystal structure. The slow-cooled samples showed the presence of Ag7Te4 impurities, while the annealed and quenched samples contained minor amounts of the secondary Sb2O3 phase. The Cd-doped AgSb1-x Cd x Te2 (x = 0, 0.02, 0.04, and 0.06) samples were subsequently synthesized by the annealing and quenching method and were found to maintain the fcc structure with Sb2O3 impurities. The amount of the secondary Sb2O3 phase decreased sharply upon Cd doping, signifying the role of impurities in stabilizing the metastable parent compound AgSbTe2. The microstructure, morphology, and elemental composition were studied using electron microscopy (FESEM and TEM). The elemental distribution was homogeneous, but the dimensions and packing density of the crystallites varied across the sample. The elemental composition and oxidation state of AgSb1-x Cd x Te2 were confirmed by X-ray photoelectron spectroscopy. Hall effect and resistivity measurements at room temperature showed that carrier (hole) concentration increased, while carrier mobility was reduced upon Cd doping.