Improvement of thermal stability of zirconia aerogel by addition of yttrium

Crack-free, monolithic yttria-stabilized zirconia (YSZ) aerogels were prepared by a sol-gel method with supercritical drying technique using Zirconium oxychloride and yttrium nitrate as starting materials. To improve thermal stability, yttrium was added to zirconia aerogel. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption have been used to study the effect of an yttrium addition to zirconia aerogel. The addition of a small amount of yttrium resulted in a significant suppression of phase transformation from tetragonal phase to monoclinic phase. The higher thermal stability was achieved by the addition of 8 wt% yttrium, the transformation from tetragonal phase to monoclinic phase did not take place after heat-treated at 1000 A degrees C for 2 h, and the surface area can maintain as large as 28 m(2)/g. The sol-gel method was successfully applied to the synthesis of crack-free, monolithic 8YSZ aerogel. Even after heat-treated at 1000 A degrees C for 2 h, they still keep the whole block without collapse. The tetragonal phase can be stabilized in 8YSZ aerogel after heat-treated at 1200 A degrees C for 2 h. The 8YSZ aerogel presents a more porous structure (S (BET) = 28 m(2)/g) with elementary crystallites (25 nm). It is clear that due to the addition of yttrium, the thermally stability of zirconia aerogel have been improved. [GRAPHICS] .