Structure and transport behavior of In-filled cobalt rhodium antimonide skutterudites

The effect of indium icosahedral void-site filling on the transport properties of cobalt and rhodium antimonide solid solutions is investigated. Co4−xRhxSb12 and indium-filled In0.1Co4−xRhxSb12 solid solutions were synthesized. Partial rhodium substitution produces a distinct clustering-induced lattice strain that is partly relieved upon indium substitution into the skutterudite icosahedral void-sites. Indium lowers the thermal conductivity of all samples near room temperature. A distinct increase in thermal conductivity is observed in all indium-filled rhodium substituted samples at elevated temperatures and is attributed to bipolar thermal conductivity. In addition, the indium-filled samples were subjected to a 6-day heat treatment at 673 K. Void-site filled indium was found to be metastable at this temperature, and was found to partially precipitate during the 6-day heat treatment; thereby presenting concerns over the long-term stability of thermoelectric devices based on indium-filled skutterudites.