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

TL;DR

This study investigates the thermoelectric properties of layered R_2PdO_4 oxides, revealing low resistivity and potential for thermoelectric applications, despite low mobility.

Contribution

It reports the synthesis and characterization of R_2PdO_4 oxides with significantly reduced resistivity and analyzes the effects of Ce substitution on thermoelectric properties.

Findings

Resistivity of 10^3-10^4 Ωcm at room temperature.

Ce substitution decreases resistivity and thermopower.

Activation energy gap of 70-80 meV and effective mass of 15.

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.