Enhanced thermal stability of high yttria concentration YSZ aerogels

Aerogels are a promising class of materials for lightweight, high-performance insulation. However, their high specific surface area contributes to rapid densification of the structure at elevated temperatures. Upon densification, the favorable properties of low thermal conductivity and low density are lost. Investigation of doped metal oxide systems presents a route to stabilization of porous structures at high temperatures and a platform to study parameters conducive to thermal stability. Our work focuses on yttria-stabilized zirconia (YSZ) aerogels prepared via a sol-gel method and supercritically dried. Yttria concentrations were studied from 0 to 50 mol% YO_1.5 to stabilize porosity to temperatures of 1200°C and develop an understanding of properties contributing to improved stability. Increased yttria content improved the thermal stability of the pore structure by reducing densification and suppressing crystallite growth, resulting in retention of the mesoporous structure to 1200°C. The improvement in thermal stability is related to associated reductions in specific surface energy and cation diffusivity at higher yttria concentrations. This work demonstrates that tuning thermodynamic and kinetic factors is a viable route to improved thermal stability in highly porous structures for use as insulation in extreme environments.