Thermoelectric properties of the layered Pd oxide R_2PdO_4 (R = La, Nd, Sm and Gd)

Abstract

We prepared polycrystalline samples of R${}_2$PdO${}_4$ (R = La, Nd, Sm and Gd) using a NaCl-flux technique. The measured resistivity is of the order of 10${}^3-10^4$ $\Omega$cm at room temperature, which is two orders of magnitude smaller than the values reported so far. We further studied the substitution effects of Ce for Nd in Nd${}_{1.9}$Ce${}_{0.1}$PdO${}_4$, where the substituted Ce decreases the resistivity and the magnitude of the thermopower. The activation energy gap of 70-80 meV and the effective mass of 15 evaluated from the measured data are suitable for thermoelectric materials, but the mobility of 10${}^{-6}$ cm${}^2$/Vs is much lower than a typical value of 1-10 cm${}^2$/Vs for other thermoelectric oxides.

5 pages, 5 figures, to appear in J. Phys. Soc. Jpn