Crack-free porous YSZ membrane via controlled synthesis of zirconia sol

Sol-gel processing is one of the most powerful tool to synthesize inorganic thin membranes, Several membranes, such as alumina, silica, titania, etc., have been prepared so far. The key in the sol-gel process is how to conquer cracking in the drying stage. We approach this problem in view of the control of sol-gel chemistry. The particulate zirconia sol is a useful precursor to synthesize nanostructured yttria stabilized zirconia (YSZ) at low temperature, but we could not prepare a crack-free film on a porous support due to its mechanical fragileness. Polymeric sol containing linear chains of zirconium and oxygen was synthesized via controlled hydrolysis and condensation of zirconium n-butoxide using triethanolamine (TEA, 2,2',2 ''-nitrilotriethanol) as a chelating agent. Polymeric sol is useful to remove cracking, but the film formation property on a porous support is so poor since most of the sol is sucked into the support and no gel layer is formed on the top. By mixing two sols, we successfully balance the film formation property and the mechanical strength to cracking. Thus, crack-free porous YSZ thin membrane with a few-tens of nanometers pores are successfully prepared. The nanostructure is still stable after the post-calcination at 1173 K.