Crafting La0.2Sr0.8MnO3-δ membrane with dense surface from porous YSZ tube

Abstract

This work reports a new design of asymmetric tubular oxygen-permeable ceramic membrane (OPCM) consisting of a porous Y2O3 stabilized ZrO2 (YSZ) tube (with ∼1 μm of pore diameters and 31% porosity) as the support and a gas-tight mixed conductive membrane. The membrane has an interlocking structure composed of a host matrix, Ag(Pd) alloy (9:1 by wt) doped perovskite-type La0.2Sr0.8MnO 3-δ(LSM80, 90wt%), and the embedded constituent, pristine LSM80. The Ag(Pd) alloy component promotes not only electronic conductivity and mechanical strength but also reduction of both porosity and pore sizes in the layer (∼10-μm-thick) where it dopes. The porous structure in this layer could then be closed through a solution coating procedure by which ingress of an aqueous solution containing stoichiometric nitrate salts of La3+, Mn3+, and Sr2+ to the pore channels takes place first and the mixture of nitrate salts left after drying is subjected to pyrolysis to generate tri-metal oxides in situ. This is followed by calcinations at l,300 °C to consolidate the embedded trioxide and to cohere them with the Ag(Pd)-LSM80 host matrix. The structure formed is dubbed LSM80(S)-Ag(Pd)-LSM80, which was confirmed gas-tight by electron micrograph and N2 permeation test. Finally, we assess the chemical compatibility between LSM80 and YSZ at the sintering temperature by X-ray diffraction and electrochemical impedance analysis. The oxygen permeation of the fabricated LSM80(S)-Ag(Pd)- LSM80-YSZ membrane is within the temperature range of 600 to 900 °C. The tests reveal good compatibility between the LSM80 and YSZ and a reasonably high oxygen permeation flux in association with this OPCM assembly.