Stability and oxygen transport properties of Pr2NiO4+δ ceramics

The oxygen permeability and stability of dense Pr2NiO4+δ ceramics have been appraised in comparison with K2NiF4-type lanthanum nickelate. In oxidizing atmospheres, Pr2NiO4+δ exhibit an extensive oxygen uptake and decomposition into the Ruddlesden–Popper-type Pr4Ni3O10 and praseodymium oxide at temperatures below 900 °C. At 900–950 °C when the K2NiF4-type praseodymium nickelate is stable in the ceramic membranes placed under an oxygen partial pressure gradient, the steady-state oxygen permeability of Pr2NiO4+δ is similar to La2NiO4+δ. The phase changes on cooling lead to considerably higher oxygen permeability, which becomes comparable to that of perovskite-type cobaltites, and to noticeable isothermal expansion. The stability of Pr2NiO4+δ in reducing atmospheres, estimated from the p(O2) dependencies of total conductivity and Seebeck coefficient, is lower than that of La2NiO4+δ, probably due to a smaller size of the A-site cation.