Thermoelectric properties of CuSbSe2 and its doped compounds by Ti and Pb at low temperatures from 5 to 310 K

Transport and thermoelectric properties of CuSbSe2 and CuM0.02Sb0.98Se2 (M=Ti,Pb) have been investigated at the temperatures from 5 to 310 K. The results indicated a good linear relationship between logarithm of dc resistivity and reciprocal of temperature existed for CuSbSe2 at the temperatures above similar to 73 K and below similar to 62 K, respectively, from which two activation energies Delta E-1 (66 meV) and Delta E-2 (0.16 meV) were derived. Only Delta E-2 was changed after Ti substitution, while Pb substitution for Sb only changed Delta E-1, both of which could be ascribed, respectively, to the substitution of Ti3+ and Pb4+ for Sb3+. The thermopower of CuPb0.02Sb0.98Se2 decreased substantially as compared with that of CuSbSe2, which can be explained as large increase in electron concentration due to substitution of Pb4+ for Sb3+, leading to transport of double carriers (electrons and holes) in this p-type semiconductor. Experiments showed that CuM0.02Sb0.98Se2 has much smaller (lattice) thermal conductivity as compared with CuSbSe2, coming presumably from the strong phonon scattering by the impurities (Ti or Pb). As compared with that of CuSbSe2 the figure of merit ZT of CuTi0.02Sb0.98Se2 has been improved substantially at T >similar to 150 K due to large decrease in both the resistivity and thermal conductivity. Specially, its ZT value is about twice as large as that of CuSbSe2 at 300 K, suggesting that Ti substitution is a promising way to improve its thermoelectric properties. (c) 2006 American Institute of Physics.