Synthesis and oxygen permeation properties of ceramic-metal dual-phase membranes

Percolative and non-percolative fluorite type Bi1.5Y0.3Sm0.2O3 (BYS) and si lver dual-phase membranes were prepared by mixing BYS and Ag powders. Oxyge n permeation and electric conduction through these BYS/Ag dual-phase membra nes were studied in thr temperature range of 650-850 degrees C. The percola tive BYS/Ag 40% and non-percolative BYS/Ag 30% membranes exhibit about 50-f old and 10-fold increase, respectively, in oxygen permeation flux compared to BYS membranes. For a 1.3 mm thick BYS/Ag 40% membrane, an oxygen permeat ion flux of 5.8 x 10(-7) mol/cm(2) s was measured at 850 degrees C with oxy gen partial pressures at the feed and permeate sides being 0.21 and 0.009 a rm, respectively. The activation energies for oxygen permeation in the temp erature range of 650-850"C are 79.30 and 87.30 kT/mol for the BYS/Ag 30% an d BYS/Ag 40% membranes, respectively. For the non-percolative BYS/Ag membra ne, the presence of Ag enhances the surface reaction rate for oxygen permea tion. The continuous silver phase in the percolative BYS/Ag membrane increa ses both the electronic conductivity and surface reaction rate which result in substantial improvement of oxygen permeance. (C) 2000 Elsevier Science B.V. All rights reserved.