OXYGEN SEMIPERMEABLE SOLID OXIDE MEMBRANE COMPOSITES PREPARED BY ELECTROCHEMICAL VAPOR-DEPOSITION

Ceramic membrane composites consisting of a coarse porous alpha-alumina or two-layer porous alumina membrane support and an oxygen semipermeable gas tight thin (0.2-5-mu-m) yttria stabilized zirconia (YSZ) film are prepared by the electrochemical vapor deposition (EVD) method. The minimum gas-tight thickness of the YSZ films depends strongly on the average pore size of the support on which the films are deposited by the EVD) process. The oxygen permeation fluxes through such gas tight YSZ membrane composites, measured in situ on the EVD apparatus, are in the range of 3 x 10(-9) to 6 x 10(-8) mol/cm2-sec with an oxygen partial pressures of P'(O2) (high) almost-equal-to 3 x 10(-2) atm and P'(O2) (low) almost-equal-to 10(-5) atm, much larger than the literature data for thicker YSZ pellets. During the oxygen permeation experiments the rate-limiting step is found to be the bulk electrochemical transport in the grown YSZ films with a thickness smaller than 10-mu-m.