Thermoelectric Properties of Layered Pd Oxide R₂PdO₄ (R = La, Nd, Sm, and Gd)

Abstract

We prepared polycrystalline samples of R₂PdO₄ (R = La, Nd, Sm, and Gd) using a NaCl flux technique. The measured resistivity is of the order of 10³–10⁴ Ω cm at room temperature, which is two orders of magnitude smaller than those reported so far. We also studied the substitution effects of Ce for Nd in Nd_1.9Ce_0.1PdO₄, where the substituted Ce decreases resistivity and the magnitude of thermopower. Activation energy gap of 70–80 meV and an effective mass of 15 evaluated from the measured data are suitable for thermoelectric materials, but a mobility of 10⁻⁶ cm²/(V·s) is much lower than typical mobilities of 1–10 cm²/(V·s) for other thermoelectric oxides.