Preparation of ReNiO₃ (Re = Pr, Sm, Eu) and proton conductivity

ReNiO₃ (Re = Pr, Sm, Eu) solid electrolytes were prepared by the sol-gel method, which were sintered in a pure oxygen atmosphere of 20 MPa at 1000 °C for 24 hours. The DC resistivities of the three materials in air and in a hydrogen-containing atmosphere were tested respectively. The resistivities in the hydrogen-containing atmosphere were about 10², 10⁴, and 10⁵ times higher than those in air and XPS analysis showed that after 10%H₂-Ar treatment, the proportion of Ni²⁺ of PrNiO₃, SmNiO₃ and EuNiO₃ increased successively. The proton transport number of PrNiO₃ was lower than 0.5 at 50-500 °C, and SmNiO₃ and EuNiO₃ were almost pure proton conductors below 200 °C. The conductivities of SmNiO₃ and EuNiO₃ were 1.08 × 10^-4 S cm^-1 and 1.83 × 10^-5 S cm^-1 at 200 °C in 5%H₂-Ar. The hydrogen sensing properties of SmNiO₃ and EuNiO₃ show that the measurement results of the two materials were accurate in the range of 0.5-10% H₂.