Thermoelectric power of Gd-doped CeO 2 (Gd 0.1Ce 0.9O (2 − δ) (GDC10)): Measurements on porous samples

Abstract

Thermoelectric power was measured on dense and porous samples of two materials: silver, a noble metal, and Gd-doped CeO 2 of composition Gd 0.1Ce 0.9O (2 − δ) (GDC10), a mixed ionic electronic conductor. Since silver does not change composition when subjected to a change in temperature, only thermal equilibration is required. Both dense and porous samples of silver equilibrated in about the same time, and the measured thermoelectric power was also about the same. However, the time required for equilibration in dense GDC10 samples was an order of magnitude greater as compared to that for porous samples. The measured thermoelectric power on dense samples was also different from that on porous samples, especially below 600 °C. It was also observed that the measured thermoelectric power in dense GDC10 samples depended on thermal history unlike porous GDC10 samples. That is, prior thermal annealing history affected subsequent measurements at lower temperatures in the case of dense samples. Issues relating to the kinetics of EMF equilibration in dense and porous samples of silver and GDC10 are discussed.