Radiation Thermocouples with (Bi, Sb)₂(Te, Se)₃

Abstract

New semiconducting thermoelectric materials were developed to improve the performance of radiation thermocouples. They were Bi1.8Sb0.2Te2.7Se0.3+0.08 wt.% CuBr for n-type and Bi1.4Sb0.6Te3 for p-type. Radiation thermocouples were made with combinations of two types of the new materials as well as those already known by welding them on receivers having an area of 2 mm×0.2 mm. The radiation thermocouple with Bi1.8Sb0.2Te2.7Se0.3+0.08 wt.% CuBr and Bi1.4Sb0.6Te3 showed the best characteristics with NEP (Noise Equivalnet power) of 2×10-11 Watt, responsivity of 30 µV/µW, internal resistance of 8 Ω and time constant of 20 milliseconds. The NEP decreased as the figure of merit of the thermocouple increased. It was found that contact noise was generated at the welded part of the receiver. This noise was noticeable when the area of the welded part became smaller than about 10-6 cm2, and set the lower limit of NEP.