Preparation and thermoelectric properties of p- and n-type CoSb3

Abstract

Large single crystals of the compound CoSb3 were grown from antimony rich melts by the Bridgman gradient freeze technique. CoSb3 has the skutterudite crystal structure and a peritectic decomposition temperature of 873 °C. Samples were characterized by X‐ray diffractometry, microprobe analysis and density measurements. A Debye temperature of 306 K was calculated from speed of sound measurements. As‐grown CoSb3 crystals show p‐type conductivity. N‐type samples were obtained over a wide range of doping level by addition of Te. Seebeck coefficient, electrical resistivity, thermal conductivity and Hall effect measurements were performed between room temperature and 500 °C. The results of these measurements are presented and discussed. Exceptionally high Hall mobilities were obtained on p‐type samples which is consistent with the high degree covalency of the skutterudite crystal structure. A maximum room temperature Hall mobility of 3445 cm2.V−1.s−1 was measured on a sample with a carrier concentration of 4×1017 cm−3. N‐type samples were found to have substantially lower Hall mobilities in the range of temperature investigated. A bandgap of 0.55 eV was calculated from the high temperature electrical resistivity and Hall effect measurements. The hole and electron effective masses were also estimated. Based on the experimental data obtained, the potential of CoSb3 as a thermoelectric material is discussed.