Crystal field effects and thermoelectric properties of ${\mathrm{PrFe}}_4{\mathrm{Sb}}_{12}$ skutterudite

Transport and magnetic properties are reported for ternary skutterudites ${\mathrm{La}}_{0.83}{\mathrm{Fe}}_4{\mathrm{Sb}}_{12}$ and ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_4{\mathrm{Sb}}_{12}.$ Physical properties of ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_4{\mathrm{Sb}}_{12}$ are dominated by crystal electric field effects, yielding in the magnetic triplet ${\Gamma }_5$ as ground state. As a result, long-range magnetic order appears below 4.6 K. ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_4{\mathrm{Sb}}_{12}$ exhibits an unusually high electronic contribution to the specific heat $C_p/T$ of several hundred ${\mathrm{m}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{}\mathrm{K}}^2,$ and a significant value of a nuclear Schottky contribution is derived below about 1 K, primarily related to ${}^{141}\mathrm{Pr}$ with a nuclear spin $I=5/2.\mathrm{}$ The figure of merit at room temperature, expressing the thermoelectric performance of ${\mathrm{Pr}}_{0.73}{\mathrm{Fe}}_4{\mathrm{Sb}}_{12},$ is about 0.075.