Effects of doping Pd/Pt in CoSb3 crystals on electrical and thermoelectric properties

Double doping of palladium and platinum is Skutterudite CoSb₃ has been studied to improve thermoelectric properties. It was found that the solubility limit of Pd and Pt in CoSb₃ crystal amounted to about 10 at% and substitution of Pd and Pt for Co occurred. The carrier concentration increased to about 5×10²⁰ cm ^-3 due to a higher degree of solutioning of Pd and Pt by double doping than that of Pd or Pt by single doping. Electrical conductivity of σ=1950 S/cm at room temperature could be obtained for the double doping of 5 at% Pd and 5 at% Pt. Heavy doping by Pd and Pi was found to significantly reduce the lattice thermal conductivity, leading to the decrease in thermal conductivity from 0.1 (non-doped crystal) to 0.05 W/cm K. As a result, the figure of merit value Z was about 1.2×10^-3/K at temperatures between 500 and 800 K, and the maximum ZT=0.9 was obtained at 750 K