Fabrication of thin and dense nano-crystalline membranes on porous substrates

A fabrication process is proposed for obtaining thin and dense nano-crystalline membranes on porous substrates. The key issue of this process implies the formation of a layer of composite structure in between membrane and substrate in order to reach a high mechanical stability of the membrane through heating and cooling cycling treatments. The membrane is obtained by metal-organic chemical vapour deposition in an amorphous state. The intermediate composite layer is formed by creep of the amorphous membrane through the substrate porosity, followed by a thermal treatment for crystallisation. This process was applied with success to a fabrication of La0.7Sr0.3Fe0.8Co0.2O3−δ and La0.4Sr0.6Fe0.25Co0.75O3−δ nano-crystalline membranes of less than 1 μm thickness on porous yttria-stabilised zirconia substrates. Catalytic measurements performed on these thin membranes show that ionic conductivities measured at 500 °C are comparable with values reported in the literature obtained on thick membranes of similar composition.