Effect of milling time and microwave sintering on microhardness and electrical properties of nano and micro structured cordierite

The purpose of this research is to investigate the mechanical and electrical properties of nano structured cordierite. Nano grain size powders were synthesized through mechanical activation by high-energy ball milling of the starting powders containing 34.86 wt% Al2O3, 51.36 wt% SiO2, and 13.78 wt% MgO. Samples were prepared by conventional and microwave sintering at 1390°C. SEM observations illustrated the equiaxed nano-grains of cordierite with an average grain size of 40 nm for samples sintered in microwave. With the increase of milling time, samples sintered at 1390°C in microwave furnace obtained higher micro-hardness and density than those sintered at the same temperature in conventional furnace. Sample milled for 30 h and sintered in microwave furnace at 1390°C obtained the maximum dielectric constant of 5.5±0.1.