Synthesis and thermoelectric properties of Ce(Ru_(0.67)Rh_(0.33))_4Sb_(12)

Exotic filled skutterudite compositions show promise for thermoelectric applications. Current work was undertaken with a nominal composition of Ce(Ru_(0.67)Rh_(0.33))_4Sb_(12) to experimentally verify its potential as an n-type thermoelectric material. Nominal electroneutrality was expected at 0.89 cerium filling and fully filled materials were expected to be strongly n-type. Filled precursors of the nominal composition were synthesized using straightforward solid state reaction techniques, but standard synthesis routes failed to produce a fully-filled homogenous phase. Instead, the filled thermoelectric Ce(Ru_(0.67)Rh_(0.33))_4Sb_(12) was synthesized using a combination of solid state reaction of elemental constituents and high pressure hot pressing. A range of pressure-temperature conditions was explored; the upper temperature limit of filled skutterudite in this system decreases with increasing pressure and disappears by 12 GPa. The optimal synthesis was performed in multi-anvil devices at 4-6 GPa pressure and dwell temperatures of 350-700 °C. ruthenium The result of this work, a Ce(Ru_(0.67)Rh_(0.33))_4Sb_(12) fully filled skutterudite material, exhibited unexpected p-type conductivity and an electrical resistance of 1.755 mΩ-cm that increased with temperature. Thermal conductivity, Seebeck coefficient, and resistivity were measured on single phase samples. In this paper, we report the details of the synthesis routeand measured thermoelectric properties, speculate on the deviation from expected carrier charge balance, and discuss implications for other filled skutterudite systems