A method has been developed to reproducibly sinter high purity alumina (>99.8%) to densities in excess of 98% of theoretical. Sintering times of between 6 and 120 minutes have been investigated and a uniform grain structure is only obtained with sintering times greater than 30 minutes.
Microwave sintering produces a product with a smaller, more uniform grain structure witha more narrow size distribution. The alumina is also tougher than the conventionally sintered material.
When scaled—up to sinter batches of 400 grams, an energy consumption of 3.8 kWh/kg is required, which is estimated to be a 90% savings over conventional sinteringin an electric resistance furnace.