Pressure-assisted microwave sintering: A rapid process to sinter submicron sized grained MgAl2O4 transparent ceramics

This work focuses on the development of an original process based on a 2.45 GHz single-mode microwave cavity equipped with a uniaxial press, to sinter transparent spinel MgAl2O4 ceramic in air. The samples were conventionally pre-sintered to a density of 90% TD before microwave sintering to the final stage of densification. The influence of thermomechanical cycle on the material properties was investigated. Transmittance, grain size distribution, hardness and fracture toughness of the samples were measured and correlated to the microstructure. This new sintering process has allowed obtaining transparent samples with sub micrometric grain size and high mechanical properties, with relatively short times and low temperature. These first results can be compared to some obtained by SPS or HIP. The technical input of this method is that all the process is here conducted in air atmosphere.