MICROSTRUCTURE OF NIO-COO SOLID-SOLUTION SINTERED WITH AL2O3 ADDITIVE

The influence of (Ni, Co)Al2O4 spinel precipitates on the grain growth in (Ni, Co)O ceramics with 1.45 mol% Al2O3 was investigated in the te mperature range 1280 to 1380 degrees C, Smaller precipitates preferent ially dissolved and larger precipitates grew with increasing temperatu re and holding time, therefore, the growth mechanism of spinel precipi ates was considered to be Ostwald ripening. The matrix grain size incr eased linearly as a function of particle size of spinel at 1280 degree s C and 1360 degrees C. Furthermore, the slope increased with increasi ng temperature, which indicates that the grain growth inhibition effec t became weak. It is believed that higher solubility of Al2O3 into the matrix at higher temperature decreases the volume fraction of the spi nel precipitates inhibited the grain growth of matrix.