The effect of ZnO addition on the densification and properties of magnesium aluminate spinel

Stoichiometric magnesium aluminate spinel can be developed by solid oxide reactions of calcined magnesia and calcined alumina. The raw materials were mixed; attrition milled, compacted under a uniaxial pressure of 100 MPa and finally fired in the temperature range of 1500 to 1650°C. Up to 2 wt% ZnO was incorporated as an additive. In this investigation the effect of ZnO on the densification and properties of the magnesium aluminate spinel has been studied. It was found that 99% of theoretical density was achieved on firing at 1550°C with the addition of 0.5 wt% ZnO. The optimum properties in terms of bulk density, hot strength and thermal shock resistance was obtained with 1 wt% ZnO. All the ZnO containing samples retained their strength up to 6–8th cycle on thermal shock. ZnO containing samples are comparatively more resistant to thermal shock than ZnO free samples.