Journal of the American Ceramic Society, Vol.103, No.4, 2653-2662, 2020
Influence of grain interior and grain boundaries on transport properties of scandium-doped calcium zirconate
Calcium zirconate-based protonic conductors are currently the most promising electrolyte for high-temperature hydrogen sensors, however, protonic conductors exhibit mixed protons, oxygen vacancies and electron-holes conduction above 700 degrees C, and the protons transport number is significantly influenced by the atmosphere. Therefore, the relationship between protons transport number and oxygen/water vapor partial pressure should be established to improve the veracity of the hydrogen sensor. Herein, CaZr0.9Sc0.1O3-alpha perovskite oxides are prepared and the influence of grain interior and grain boundaries on transport properties is systematically investigated by using with defect chemistry theory. And the relationship between protons transport number and oxygen/water vapor partial pressure should be obtained. The results indicate that the dominant conduction carriers of CaZr0.9Sc0.1O3-alpha were protons in Ar and reductive atmospheres at 500 degrees C-800 degrees C, and the conductivity (sigma h center dot) and transport number (th center dot) of holes are remarkably increased with increasing oxygen partial pressure. In addition, protons, oxygen vacancies and electron-holes transport properties of grain interior and grain boundaries in scandium-doped calcium zirconate reveal that grains can effectively block oxygen vacancies transport at 550 degrees C-800 degrees C, but grains cannot block the holes transport. Therefore, the oxygen vacancies trend to transport through grain boundaries.