Effect of Cr2O3 derived from Cr(NO3)3·9H2O precursor on the densification and mechanical properties of zirconia-toughened alumina (ZTA) composites

Abstract

The effects of Cr2O3 derived from Cr(NO3)3·9H2O precursor on the densification, microstructure and mechanical properties of zirconia-toughened alumina (ZTA) ceramics were investigated. The Cr2O3 content in ZTA varied from 0 to 0.8wt%. Cr2O3 derived from Cr(NO3)3·9H2O can form solid solutions with Al2O3 and ZrO2 in ZTA more efficiently than Cr2O3 additive directly added to ZTA. The precursor-derived Cr2O3 can significantly promote the densification of ZTA and nearly fully dense ZTA composites were obtained by pressureless sintering at 1540°C for 2h. In contrast, the effect of directly added Cr2O3 additive on densification of ZTA was limited due to its low amount of dissolution in ZTA. ZTA with 0.5wt% Cr2O3 derived from Cr(NO3)3·9H2O had fine microstructure and its fracture toughness was as high as 4.67±0.03MPam1/2 which was about 30% higher than that of undoped ZTA and ZTA with 0.5wt% Cr2O3. ZTA with 0.5wt% precursor-derived Cr2O3 had the maximum Vickers hardness about 18.10±0.15GPa. Higher content of Cr2O3 (0.8wt% or higher) would have adverse effect on the densification due to the vaporization and condensation of Cr-containing species during pressureless sintering.