THERMOELECTRIC-POWER IN IONIC AND ELECTRO NIC MIXED CONDUCTORS

In order to study the thermoelectric property of the oxide ionic and e lectronic mixed conductor of 10 mol% CaO-doped CeO2 (CDC), a new type of thermocell was prepared, in which platinum electrodes were embedded in the tube-type sample to diminish the large temperature gradient ov er the electrodes due to the local heat radiation from heating furnace . Using this thermocell, reproducible data were obtained. The thermoel ectric power measured in CDC under various oxygen atmospheres (Po-2) f rom 1.0 to about 10(-15) atm showed that the sign of Seebeck coefficie nts changed from minus to plus. This variation of Seebeck coefficients vs. Pot was well interpreted by considering that (1) the thermoelectr ic power could be a driving force to make actual and electrochemical o xygen transfer in the mixed conductor and (2) the electrode processes had limiting rates due to slow oxygen diffusion (or oxygen gas exhaust ion at the cathode and evolution at the anode).