Investigation of near-room and high-temperature thermoelectric properties of (Bi0.98In0.02)2Se2.7Te0.3/Bi2Te3 composite system

Abstract

Polycrystalline composite samples of (Bi0.98In0.02)2Se2.7Te0.3/Bi2Te3 with different concentrations of Bi2Te3 such as 5%,10%,15% and 20% were prepared by the solid-state reaction technique. The X-Ray diffraction analysis has shown the hexagonal composite crystal structure with space group of R3 ¯ m. Field emission scanning electronic microscope shows secondary particles on the surface of the samples. All the samples have shown the usual semi-conducting behaviour throughout the temperature range. It is observed that bismuth has been co-ordinated with 6 selenium atoms in (Bi0.98In0,02)2Se2.7Te0.3 compound and it has enormous selenium vacancies. The electrical resistivity represents the noteworthy result of the grain boundaries leading to the higher content of scattering centres in the polycrystalline composite samples. It is found that the electronegativity differences of In and Te, In and Se are less than Bi and Se, Bi and Te is the reason for the decrease in Seebeck coefficient in the compound containing 15% and 20% of Bi2Te3.