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 Y 2 O 3 doping on the electrical conductivity of CaHf 1− x Y x O 3−δ , which was prepared by conventional solid-state reaction. The electrical conductivity of CaHf 1− x Y x O 3−δ 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 CaHf 1− x Y x O 3−δ first increases and then decreases with x from 0.08 to 0.20, and its total conductivity and conductivity activation energy are 3.88 × 10 −7 to 5.34 × 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 CaHf 1− x Y x O 3−δ is 3.9 × 10 −6 to 2.4 × 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 CaHf 1− x Y x O 3−δ exceeded 97% in hydrogen atmosphere at temperatures from 973 to 1173 K. In sum, these findings of CaHf 1− x Y x O 3−δ can be used as alternative materials for hydrogen sensor electrolytes.