EFFECT OF SPINEL ADDITION ON THE SINTERING BEHAVIOR AND MICROSTRUCTURE OF ALUMINA-SPINEL CERAMICS

Sintering behaviors of alumina-spinel powder mixtures were investigated up to 1600 degrees C using a vertical dilatometer. Final density and microstructure of pure alumina, magnesium aluminate spinel (MgAl2O4) ceramics and ceramic composites with different alumina-spinel ratio were examined. As a result, the densification and final density of alumina-spinel composites were affected by addition of 10 wt. % and 20 wt. % spinel into alumina. Non-stoichiometric alumina-rich spinel phase was detected in the matrix of the composites by EDS. The presence of spinel phase inhibited alumina grain growth, therefore the pure alumina sample had nearly twice the grain size as the multiphase alumina-spinel samples. Vickers hardness of the samples was tested and compared. The hardness of the composite with 10 wt. % spinel was slightly higher than the pure alumina ceramic, due to grain size and density of the samples.