Dense nanostructured zirconia by two stage conventional/hybrid microwave sintering

The processing of 3 mol% yttria partially stabilised zirconia nanopowder into components has been investigated via slip casting low viscosity but high solids content nanosuspensions and subsequent pressureless sintering via one and two stage sintering involving both pure conventional heating and hybrid conventional-microwave heating. Very homogeneous and uniform green bodies with densities up to ∼54% of theoretical could be produced, the major limitation being cracking on drying when the highest solid content suspensions were used. This could be partially overcome via the use of humidity drying. The pressureless sintering of the bodies revealed that the two stage sintering process allows a much finer average grain size to be retained than conventional single stage firing, whilst the use of hybrid heating gave further improvements. Greater than 99% dense ceramics with average grain sizes of ∼65 nm could be produced from a powder with an average particle size of ∼16 nm.