INFLUENCE OF AL2O3 ADDITION ON THE SINTER ING BEHAVIOR OF NIO-COO SOLID-SOLUTION

Sintering behavior of (Ni, Co) O was investigated measuring linear shr inkage as a function of Al2O3 addition. Morphological study was also a ttempted for the samples sintered at 1280 degrees C for 10h. The added Al2O3 reacted with the (Ni, Co)O matrix to form (Ni, Co)Al2O4 spinel from 800 to 1200 degrees C. The addition of Al2O3 inhibited the growth of (Ni, Co)O particles, and then decreased the linear shrinkage from 800 to 1100 degrees C. Above 1150 degrees C, in contrast to the consta nt linear shrinkage of (Ni, Co)O, (Ni, Co)O with Al2O3 showed steep li near shrinkage behavior. Furthermore, at 1400 degrees C, the linear sh rinkage for (Ni, Co)O without Al2O3 and with Al2O3 was 14 and 18%, res pectively. The microstructure of the quenched samples showed that numb er of (Ni, Co)Al2O4 spinel precipitates decreased above 1150 degrees C . The average grain size of the samples sintered at 1280 degrees C for 10h decreased from 11 to 4 mu m with increasing Al2O3 additive from 0 .5 to 8 mass%; the addition of Al2O3 inhibited the grain growth of mat rix in the final stage of sintering.