Faculty Sponsor's Department:
Thermoelectric materials generate electrical energy from waste heat and natural heat sources. For high temperature applications, oxide thermoelectric materials are favorable due to their air stability. Complex palladium oxides are promising thermoelectric materials because they are easily hole doped. Doping induces metal-insulator transition, and enables better control over contraindicated thermoelectric properties. Here, we systematically investigated the effect of doping SrPd3O4 and CaPd3O4 with varying percentages of sodium by ion substitution at the Sr2+ and Ca2+ sites. Phase-pure Sr1-xNax Pd3O4 and Ca1-xNax Pd3O4 samples with x between 0.05 and 0.15 were synthesized through a solid-state reaction in an oxygen furnace. Electrical measurements on Sr1-xNax Pd3O4 samples reveal that for temperatures ranging from 300 K to 30 K, resistivity decreases with increased sodium doping. For the highest doped samples, resistivity decreases by almost two orders of magnitude from 1 Ωcm to 0.01 Ωcm. Since resistivity between 0.001 Ωcm and 0.01 Ωcm are reported to achieve a good balance between competing thermoelectric properties for optimal performance, Sr1-xNax Pd3O4 is potentially useful for thermoelectric applications. Furthermore, thermogravimetric analysis (TGA) confirms that doped samples of Sr1-xNax Pd3O4 are stable up to temperatures as high as 1155 K.