HIGH-PERFORMANCE THERMOELECTRIC CONVERSION MATERIAL AND THERMOELECTRIC CONVERSION MODULE FOR POWER GENERATION

摘要

This invention provides a thermoelectric material, which has been improved in figure of merit, and a thermoelectric module for power generation. The figure of merit of a Bi-Te-base thermoelectric material produced by providing Bi<SUB>2</SUB>Te<SUB>3</SUB> as a main material, melting the main material in vacuo or in an inert gas atmosphere and then cooling the melt under conditions of a temperature gradient within the molten metal and ingot of 2 to 20°C/cm and a cooling rate of 0.1 to 5°C/min or less reaches about 1.4 at room temperature. The figure of merit of the thermoelectric element is significantly increased by plating a thermoelectric material on its surface which comes into contact with a heat source, soldering the surface to a metal to obtain an assembly, and bringing the ratio of the length l<SUB>B</SUB> of the thermoelectric material, to the overall length l of the thermoelectric conversion element (x=l<SUB>B</SUB>/l) to 0.010 to 0.333. Specifically, when x is 0.200 or less, the figure of merit exceeds 4. In particular, when x is 0.032 (l<SUB>B </SUB>= 0.10 mm, l = 3.10 mm), when the direction of the temperature gradient is fixed, the energy conversion efficiency reaches 5.3% at a temperature difference ?T of 7.4 K. Further, under a temperature gradient periodically changed at a period T of 240 sec, the energy conversion efficiency is increased to 14.3%.