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 10 3 -10 4 Ωcm 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 Nd1.9Ce0.1PdO4, 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.

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

“…We infer that such an insulating behavior is ascribed not to the carrier concentration, which is essentially constant above room temperature, but to the mobility, as will also be discussed in the results of the Seebeck coefficient. Such a nonmetallic resistivity due to the mobility has also been observed in several oxide materials [34,35]. Figure 3(b) displays the temperature dependence of the in-plane Seebeck coefficient.…”

Thermoelectric transport in the layered Ca$_3$Co$_{4-x}$Rh$_x$O$_9$ single crystals

“…We infer that such an insulating behavior is ascribed not to the carrier concentration, which is essentially constant above room temperature, but to the mobility, as will also be discussed in the results of the Seebeck coefficient. Such a nonmetallic resistivity due to the mobility has also been observed in several oxide materials [34,35].…”

Layered palladates and their relation to nickelates and cuprates

“…But none of the Ruddlesen-Popper phases of Ag exist. So, we turn to Pd, where the n=1 member (La 2 PdO 4 ) [11] and the n=∞ member (LaPdO 3 ) [12] have been synthesized. Ln 2 PdO 4 has been reported for a variety of lanthanide ions [11] and has the T structure found in Nd 2 CuO 4 [13].…”

“…So, we turn to Pd, where the n=1 member (La 2 PdO 4 ) [11] and the n=∞ member (LaPdO 3 ) [12] have been synthesized. Ln 2 PdO 4 has been reported for a variety of lanthanide ions [11] and has the T structure found in Nd 2 CuO 4 [13]. They are insulators and show diamagnetic behavior consistent with a low spin (LS) d 8 configuration.…”