High thermoelectric performance at low temperature of p-Bi 1.8Sb 0.2Te 3.0 grown by the gradient freeze method from Te-rich melt

Abstract

The structural and low-temperature thermoelectric properties were investigated in the temperature range from 4.2 to 300 K of Bi 1.8Sb 0.2Te 3.0 grown by the gradient freeze method from Te-rich melt of Bi 1.8Sb 0.2Te 3.0+ δ . The composition profile was determined by electron probe microanalysis (EPMA) measurement to be homogeneous in the center part of the single crystalline ingots. An excess of Te is segregated at the top of the ingots. A high thermoelectric performance was achieved at low temperature in the p-type samples. The largest value of the Seebeck coefficient α of >500 μV K −1 was obtained at 200 K for δ=0.259 to give ZT=1.1. The optimum carrier concentration was determined to be n=1.6×10 19 cm −3 for the highest thermoelectric performance.