Micro-porous silica–yttria membrane by sol–gel method: Preparation and characterization

Micro-porous yttria doped silica membrane, fabricated on alpha-alumina substrate and gamma-alumina interlayer, has been prepared via the polymeric sol–gel method. In order to investigate the hydrothermal stability of the membrane, silica sols with different amounts of 5, 15 and 25 wt% yttria were prepared. These sols showed particle size distributions in the range of 0.6–3 nm. It was found that the hydrothermal stability of the unsupported silica–15% yttria membrane heat treated at 500 °C is the highest according to the results of FTIR analysis showing the formation of Si–O–Y bonds. XRD data showed thermal stability up to around 800 °C for the unsupported silica membrane with 15% yttria. N2 adsorption–desorption isotherm confirmed the existence of micro-porous structure for this membrane as BET surface area and average pore size of the unsupported membrane was 286 m2g−1 and 1.9 nm, respectively. Modified substrate surface reduced average roughness and a layer with similar roughness and pore size was achieved. Cross sectional images by FESEM showed the thickness of 680 nm for the obtained membrane.