Sintering behavior, phase formation, physical and mechanical properties of Al2O3 – Nb2O5 ceramics produced by pressureless sintering using Fe2O3 as sintering aid

Abstract

The objective of this paper was to explore the incorporation of Fe2O3 as a sintering additive in the Al2O3 − 4 wt% Nb2O5 composite, using pressureless sintering at 1400 °C. The results showed that Fe2O3 addition resulted in a reduction in shrinkage in certain compositions. The densification of the samples ranged from 84 to 95 % of theoretical density. Addition up to 2 wt% of Fe2O3 led to the formation of FeNb2O6 phase, inducing controlled grain growth, resulting in improved mechanical properties, while addition of more than 4 wt% resulted in the formation of FeNbO4, causing disordered grain growth, adversely affecting the mechanical strength of the ceramics. Microstructural analysis showed phases preferentially precipitated at the grain boundaries of Al2O3.