Cation Distribution Dependence on Thermoelectric Properties of Doped Spinel M<sub>0.6</sub>Fe<sub>2.4</sub>O<sub>4</sub>

Abstract

The electrical conductivity, Seebeck coefficient, and thermal conductivity of polycrystalline M0.6Fe2.4O4 (M = Ni, Ni0.5Mg0.5, Ni0.5Zn0.5, Zn) were measured to elucidate cation distribution-dependent changes. Preferential occupation by the doped cation in the iron spinel has been noted: Zn2+ ions prefer to occupy the tetrahedral A-site, while Ni2+ and Mg2+ prefer to occupy the octahedral B-site. While the electrical conductivity and Seebeck coefficient are almost cation distribution-independent, the thermal conductivity at room temperature is sensitive to the cation distributions. The lowest thermal conductivity of 2.0Wm11 K11 at room temperature is observed for Zn0.6Fe2.4O4. The value is about one third of that of Ni0.6Fe2.4O4. The thermal transport of MxFe31xO4 is mainly affected by cation distribution at the A-site, while the electrical transport is affected by the B-site, which is discussed in terms of the point defects at the Aand B-sites. Due to the disordering at the Aand Bsites, the thermal conductivity of MxFe31xO4 could be reduced without decreasing the electrical conductivity. Doped spinel-ferrite MxFe31xO4 would be a kind of “phonon-glass electron-crystal” material. [doi:10.2320/matertrans.M2012023]