Thermal stability and preparation of dense membrane ceramics of BIMEVOX

The thermal stability and sintering conditions of a series of BIMEVOX compounds was studied. Extended annealing at temperature below the γ/γ′ phase transition, revealed the materials doped with a MeV cation are more stable than other BIMEVOXes. A modification of the BIMEVOX doped with a MeII metal was generally observed after annealing at 450 °C for several weeks. In contrast, no evolution was noticed for BISBVOX.15, BINBVOX.25, BITAVOX.20 compositions annealed for 10 weeks at 450 °C and 7 weeks at 500 °C. These latter compositions exhibit higher melting point and require sintering temperatures above 850 °C. Moreover, the increase in thermal expansion coefficient observed in these materials at the transition of phase is smaller (14 K− 1 to 14.5 K− 1) than for the other BIMEVOXes which makes them promising candidates as membrane for oxygen separators or catalytic dense membrane reactors.