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.