Thermogalvanomagnetic properties of Sn-doped Bi95Sb5 and its application for solid state cooling

Abstract

Measurements of the complete set of thermogalvanomagnetic coefficients of Sn-doped Bi95Sb5 have been carried out from liquid nitrogen up to room temperature as a function of magnetic field strength and crystallographic direction (parallel and perpendicular to the trigonal axes). The dependences of the transport coefficients on temperature, magnetic field strength, and impurity density as well as their complex mutual correlations are explained, qualitatively. These investigations were performed in order to establish the optimum tin concentration that will maximize the thermomagnetic and thermoelectric figures of merit at a given temperature and magnetic field. As calculated theoretically a 2.5-fold enhancement of the thermomagnetic figure of merit was achieved. The crystals were grown by the horizontal zone-leveling technique under a hydrogen atmosphere. To achieve high homogeneity and to avoid constitutional supercooling a traveling double-ellipsoid mirror furnace was built up. This method enables us to produce a small liquid zone and a steep temperature gradient at the solid–liquid interface.