Thermoelectric properties of LaRh1−xNixO3

We report measurements and analyses of resistivity, thermopower and thermal conductivity of polycrystalline samples of perovskite LaRh1−xNixO3. The thermopower is found to be large at 800 K (185 µV K−1 for x = 0.3), which is ascribed to the high-temperature stability of the low-spin state of Rh3+/Rh4+ ions. This clearly contrasts with the thermopower of the isostructural oxide LaCoO3, which rapidly decreases above 500 K owing to the spin-state transition. The spin state of the transition-metal ions is one of the most important parameters in oxide thermoelectrics.