High temperature thermoelectric properties and figure-of-merit of sintered Nd2−xCexCuO4

Thermoelectric properties such as the Seebeck coefficient, electrical resistivity, and thermal conductivity are measured in the temperature range of 300– 673 K on Nd2−xCexCuO4 (x = 0–0.1) sintered bodies in order to estimate the figure-of-merit for thermoelectric energy conversion. The temperature dependences of both the Seebeck coefficient and electrical resistivity indicated n-type semiconducting behaviour. The thermal conductivities whose value decreased with increasing temperature were in the range of 3.7–7.5 Wm-1K-1. The maxima of the power factor and the figure-of-merit estimated from data measured at 320 K on a sample of a composition of x = 0.05 were 9.2×10-5 Wm-1K-2 and 1.7×10-5 K-1, respectively. The limitation of the power factor is discussed based on the measured Seebeck coefficient and electrical conductivity data. The thermal conductivity could be separated into a small electron component and a large phonon component by applying the Wiedemann–Franz law. This suggests the possibility of improving the figure-of-merit to some extent by a reduction of the phonon thermal conductivity.