Effects of Nb2O5 addition on the sinterability, microstructure and mechanical behaviour of ZTM-A12O3

ZTM–Al2O3 ceramics doped with Y2O3, MgO and Nb2O5 were studied. These ceramics could achieve high density at a sintering temperature as low as 1390°C. Results showed that there was a critical Nb2O5/ZrO2 weight ratio. When Nb2O5/ZrO2 was lower than the critical value, Nb2O5 addition had little influence on the sintering, otherwise the sinterability could be considerably improved. The microstructure of all the samples were homogenous; no obvious difference in microstructure had been brought about by Nb2O5. Despite this, X-ray diffraction measurement showed a continuous increase in m-ZrO2 with Nb2O5, due to a deficiency of oxygen vacancy in ZrO2. As a result, the mechanical properties of the ceramics, especially toughness, were greatly improved, because of the enhancement of microcrack toughening mechanism by m-ZrO2.