Effects of Y2O3 doping on the phase composition, chemical diffusion coefficient and electrochemical properties of CaHfO3 proton conductor

In order to further understand the effect of Y2O3 doping on the electrical conductivity of CaHf1-xYxO3-delta, which was prepared by conventional solid-state reaction. The electrical conductivity of CaHf1-xYxO3-delta was measured by two-terminal AC method in an oxygen-rich atmosphere, hydrogen-rich atmosphere and water vapor-rich atmosphere at the temperature between 973 and 1373 K. The test results show that the conductivity of CaHf1-xYxO3-delta first increases and then decreases with x from 0.08 to 0.20, and its total conductivity and conductivity activation energy are 3.88 x 10(-7) to 5.34 x 10(-5)S/m and 0.76-0.92eV respectively. Combined with the test results of the H/D isotope effect, it is found that protons are the main conductive carriers in the three different atmosphere at temperatures range of 973-1173 K. In addition, in the temperatures range of 1273-1373 K, the positive holes are the main conductive carriers in the oxygen rich atmosphere, and the vacancies participates in the conductive process as the main conductive carriers in the water vapor rich atmosphere. The chemical diffusion coefficients of CaHf1-xYxO3-delta is 3.9 x 10(-6) to 2.4 x 10(-5) cm(2)/s in the temperature range of 973-1373 K. According to the test results of electromotive force, the theoretical electromotive force is consistent with the measured electromotive force. The proton transfer number of CaHf1-xYxO3-delta exceeded 97% in hydrogen atmosphere at temperatures from 973 to 1173 K. In sum, these findings of CaHf1-xYxO3-delta can be used as alternative materials for hydrogen sensor electrolytes.

Automated summary

The doping of Y2O3 has a significant influence on the electrical conductivity of CaHf1-xYxO3-delta, resulting in an initial increase and subsequent decrease with increasing x. Protons are found to be the main conductive carriers in the three different atmospheres at temperatures between 973 and 1173 K. Positive holes dominate the conductive process in an oxygen-rich atmosphere, while vacancies act as the main conductive carriers in a water vapor-rich atmosphere, within the temperatures range of 1273-1373 K. The chemical diffusion coefficients of CaHf1-xYxO3-delta range from 3.9 x 10(-6) to 2.4 x 10(-5) cm(2)/s at temperatures between 973 and 1373 K. The proton transfer number of CaHf1-xYxO3-delta exceeds 97% in a hydrogen atmosphere from 973 to 1173 K. These findings suggest that CaHf1-xYxO3-delta could serve as an alternative material for hydrogen sensor electrolytes.