Magneto-thermoelectric properties of undoped and doped Bi-Sb single crystals

Electrical resistivity ρ, Seebeck coefficient α and thermal conductivity κ of Bi_1-xSb_x crystals were measured depending on alloy composition, doping, and crystallographic orientation, temperature in an interval 77-300 K, magnetic field up to 2 T. To prepare alloys, Bi and Sb refined up to 99.9999 at.% was used. The single crystals Bi_1-xSb_x (0<x<0.15) were grown by a horizontal zone recrystallization method at a growth rate V=0.05 cm/hours and temperature gradient G=20 K/cm. It is shown, that the n-type (Bi_0.93Sb_0.07)<Sn_{0.001 at%}> crystals at the temperature of practical interest T=180 K have the following magneto-thermoelectric figure of merit (Z₃₃(B₂)): 2.79·10^-3 1/K at B=0, 4.79·10^-3 1/K at B=0.25 T, and 4.95·10^-3 1/K at B=0.50 T. Caused by a magnetic field the changes of transport coefficients and Z are the result of reduction of the energy dependence of the effective relaxation time, and reduction of the partial mobility and the distinctions for light and heavy charge carriers, electrons and holes in a magnetic field. The initial conditions for obtaining the highest magneto-thermoelectric figure of merit are formed by doping by donor or acceptor impurity