Synthesis of α-alumina platelets from γ-alumina with and without microwaves

α-Al2O3 platelets of various sizes and size distributions were synthesized from powder mixture of γ-Al2O3 and Na2SO4 flux by heating with and without microwaves under the same heating schedule. The average particle size of the sample obtained by heating the powder mixture without the use of microwaves was larger than that by heating the same powder mixture with the use of microwaves. In addition, the particle size distribution of the sample obtained with the use of microwaves was narrow compared to that obtained without the use of microwaves. It was indicated that microwave processing facilitates formation of smaller size of α-alumina platelets with narrower size distribution, due to the non-thermal effect in nucleation and growth of α-alumina.