Electromotive Force of the High-Temperature Concentration Cell Using Al-Doped CaZrO3 as the Electrolyte

In order to clarify the electrochemical properties of the Al-doped CaZrO3 system, a gas concentration cell was assembled adopting 0.4 mol%Al-doped CaZrO3 polycrystalline sintered material as the electrolyte and its electromotive force (emf) was measured for various oxygen and hydrogen chemical potential gradients. The measurements were performed in a hydrogen-rich atmosphere for the temperature range from 973 to 1473 K. For almost all the conditions in the experiment, the measured emf's were well explained by regarding that the substantial predominant charge carrier is the proton. Under the conditions that the transport number of proton is less than unity, the agreement was examined between the measured emf and the theoretical one estimated based on the conduction parameters determined by the conductivity measurement reported in the previous work. It was confirmed that they well coincide with each other in all experimental conditions. This fact shows that the conduction parameters of CaZr0.996Al0.004O3-alpha and also the model of defect structure reported in the previous work were reasonable. The proton conduction domain of Al-doped CaZrO3 in the oxygen-hydrogen chemical potentials plane was examined based on these conduction parameters and it was found to be a little wider than that of In-doped CaZrO3 system. [doi:10.2320/matertrans.M2012020]