Enhancement of thermoelectric efficiency in vapor deposited Sb2Te3 and Sb1.8In0.2Te3 crystals

Pure and indium doped antimony telluride (Sb2Te3) crystals find applications in high performance room temperature thermoelectric devices. Owing to the meagre physical properties exhibited on the cleavage faces of melt grown samples, an attempt was made to explore the thermoelectric parameters of p-type crystals grown by the physical vapor deposition (PVD) method. The crystal structure of the grown platelets (9 mmx 8 mmx 2 mm) was identified as rhombohedral by x-ray powder diffraction method. The energy dispersive analysis confirmed the elemental composition of the crystals. The electron microscopic and scanning probe image studies revealed that the crystals were grown by layer growth mechanism with low surface roughness. At room temperature (300 K), the values of Seebeck coefficient S (perpendicular to c) and power factor were observed to be higher for Sb1.8In0.2Te3 crystals (155 VK-1, 2.669 x 10(-3) W/mK(2)) than those of pure ones. Upon doping, the thermal conductivity (perpendicular to c) was decreased by 37.14% and thus thermoelectric efficiency was improved. The increased figure of merit, Z = 1.23 x 10(-3) K-1 for vapour grown Sb1.8In0.2Te3 platelets indicates that it could be used as a potential thermoelectric candidate.