Structural and physical properties of n-type skutterudite Ca0.07Ba0.23Co3.95Ni0.05Sb12

Calcium and Barium were combined as fillers in the ternary skutterudite Co4−xNixSb12 in order to improve the thermoelectric properties. In addition cobalt by nickel substitution was used to enhance the electrical conductivity. The chemical composition has been determined from combined data of X-ray powder diffraction and electron microprobe analysis (EMPA). Thermoelectric properties have been characterized by measurements of electrical resistivity, thermopower and thermal conductivity in the temperature range from 4.3 to 800 K. Measurements of the charge carrier density n and Hall coefficient indicate n-type transport with n = 2.5 × 1019 cm−3. This results in a strongly enhanced Seebeck coefficient of S = −200 μV/K as well as in a figure of merit ZT = 1.2 at 775 K. Thermal conductivity and electrical resistivity have been analysed for their relevant transport mechanics. Density and micro-hardness have been measured.