Correlation between microstructure and mechanical properties of ZTA–TiO2–Nb2O5 ceramics sintered by SPS

This paper presents the experimental investigation of the effect of Nb 2 O 5 content on the phase composition, microstructure, and physical and mechanical performance of the zirconia-toughened alumina (ZTA) ceramics, aimed to optimize the additional amount of Nb 2 O 5 , refine the ceramic grains, and improve the densification, hardness and fracture toughness. ZTA ceramics with various Nb 2 O 5 contents were prepared using the spark plasma sintering method. The addition of trace amounts of Nb 2 O 5 did not produce a new Nb-rich phase; the Nb atoms were dissolved in the ZrO 2 grains. The addition of trace amounts of Nb 2 O 5 led to grain refinement and an increase in density, but the addition of excessive Nb 2 O 5 resulted in grain growth and a decrease in relative density. Furthermore, the addition of Nb 2 O 5 promoted uniformity of the microstructure. The sample with 0.25 wt.% Nb 2 O 5 had the maximum Vickers hardness and indentation fracture toughness, which were 1228.40 HV and 9.17 MPa √m, respectively. Mechanical properties of the composite mainly depended on the grain size, which was influenced to some extent by the relative density.