Electrical/thermal transport and electronic structure of the binary cobalt pnictides CoPn2 (Pn = As and Sb)

We demonstrate the electrical and thermal transport properties of polycrystalline CoPn(2) (Pn = As and Sb) between 300 and 900 K. CoAs2 shows semiconducting electrical transport up to 900 K, while CoSb2 exhibits degenerate conduction. Sign inversion of the Seebeck coefficient is observed at similar to 310 and similar to 400 K for CoAs2 and CoSb2, respectively. Thermal conductivity at 300 K is 11.7 Wm(-1)K(-1) for CoAs2 and 9.4 Wm(-1)K(-1) for CoSb2. The thermoelectric power factor of CoAs2 is similar to 10 mu Wcm(-1)K(-2), although the dimensionless figure of merit is limited to similar to 0.1 due to relatively high thermal conductivity. Using electronic structure calculations, the band gap value is calculated to be 0.55 eV for CoAs2 and 0.26 eV for CoSb2. (C) 2015 Author(s).