Zirconia Aerogels and Ceramics

However, in all these applications, this material is doped with other oxides to stabdize the tetragonal and cubic phases at low temperamres, but pure zirconia is rarely used. 

Doping zirconia with lower dopant concentrations allows the stabilization of the tetragonal phase, which enhances mechanical toughness. But if high dopant concentrations were used, the cubic phase could be stabilized at room temperature, leading to a very high ionic conductivity [51]. 

It has been reported [52] that the hardness for monoclinic zirconia is approximately 9.2 GPa, which increased slightly to values approaching 11 GPa when the tetragonal phase was stabihzed by addition of 1.5 mol% yttria [52]. However, if an important amount of yttria was used, the hardness values increased to 15 GPa [53]. 

On the other hand, when binary zirconia-silica aerogel is considered, the resulting materials exhibit superior chemical resistance to alkaline attack [54], fracture toughness [55], and optical properties. 

Zirconia Aerogeis and Solid Oxide Fuel Cells 

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