  NaTaO3-50wt% Fe2O3 composite ceramics showed a large Seebeck voltage of -300
mV at a temperature gradient of 650 K yielding a constant Seebeck coefficient
of more than -500 microV/K over a wide temperature range. We report for the
first time that SPS sintering at low temperature 870K could maintain the
short-circuit current of -80 microA, which makes this thermoelectric material a
possible candidate for high-temperature applications up to 1623 K. The reason
for the good performance is the interface between Fe2O3 and surrounding NaTaO3
perovskite. When spark-plasma sintering (SPS) is used, constitutional vacancies
disappeared and the electric conductivity increases remarkably yielding ZT of
0.016.
