Cryogenic Thermoelectric Cooler for Operating Temperatures below 90 K

Abstract

The possibility of fabricating thermoelectric coolers for operating temperatures below 90 K is considered. It is impossible to use the standard thermoelectric-cell scheme consisting of two semiconductor legs of n-type and p-type conductivity connected into an in-series electrical circuit for these temperatures. There is only one effective n-type thermoelectric material based on Bi–Sb solid solutions for the region of cryogenic temperatures. For this case, thermoelectric cells with a thermoelectric n-type leg and passive leg based on a high-temperature superconductor (HTSC) are investigated. The design of a thermoelectric cooler (module) consisting of thermoelectric n-type legs (extruded Bi_0.91Sb_0.09 crystals) and passive HTSC-based legs (YBa₂Cu₃O_{7 –x}) is proposed. A magnetic field is used to increase the thermoelectric figure of merit ZT of the module. The maximal temperature drop between the hot and cold sides ΔT > 13.5 K and maximal cooling capacity Q_c > 0.36 W are attained for the cryogenic module at a hot side temperature of T_h = 80 K, current consumption of I = 6.4 A, and voltage of U = 0.10 V.