Effects of growth-charge purity and perfection of Bi0.5Sb1.5Te3 single crystals on their thermoelectric properties

Bi0.5Sb1.5Te3 crystals, undoped and doped with 4 mol % Bi2Se3, were grown by the floating-crucible technique, using starting materials of 99.9999 or 99.99% purity. The perfection of the crystals (mosaic blocks, second-phase inclusions, dislocation density) was correlated with growth conditions. The elemental composition of several samples was determined by electron probe x-ray microanalysis. The room-temperature electrical conductivity, thermal conductivity, thermoelectric power, carrier concentration, and effective mass and mobility of holes were determined. In the range from 100 to 400 K, the electrical conductivity, thermoelectric power, thermal conductivity, and thermoelectric figure of merit of the crystals were measured.