Single crystals of p-type solid solutions between bismuth and antimony chalcogenides for cooling to T<150 K

Sb2Te3-Bi2Te3 crystals (25-60 mol% Bi2Te3) doped with Bi2Se3 and excess Te were studied with the aim of identifying the optimal compositions for the p-legs of low-temperature coolers. The crystals were gl own by the floating-crucible technique. Their transport properties were studied in the range 100-400 K. By measuring axial thermopower profiles, it was shown that increasing the Bi2Te3 and Bi2Se3 contents of the crystals has an adverse effect on their homogeneity. Crystals were prepared with a carrier concentration in the range (1-5) x 10(19) cm(-3) and a thermoelectric power above 200 muV/K at room temperature and the highest thermoelectric figure of merit at temperatures below 200 K. The maximum temperature drops and thermoelectric figures of merit were calculated for low-temperature stages of magnetothermoelectric coolers with hot-junction temperatures of 200 and 170 K and Bi-Sb n-legs.