Microstructure and fracture toughness of a spark plasma sintered Al2O3-based composite with BaTiO3 particulates

Dense Al2O3-based composites with dispersed BaTiO3 particulates were fabricated by using spark plasma sintering (SPS) at sintering temperatures between 1100 and 1500 °C with a heating rate of 100 °C/min. High-density of BaTiO3–Al2O3 with various compositions could be achieved by SPS at lower sintering temperatures compared to those by conventional pressure-less sintering (PLS). However, full densification was prevented by the onset of abnormal grain growth in Al2O3–BaTiO3 composites sintered by SPS. It was found that SPS process could accelerate the abnormal grain growth due to the activation and purification of particle surface. The addition of BaTiO3 in Al2O3 matrix improved fracture toughness of the composites fabricated by both SPS and PLS. The highest fracture toughness of 6.04 MPa.m1/2 was achieved in the composite sintered by SPS process with 5 mol% BaTiO3, while that of the monolithic Al2O3 was about 4.0 MPa.m1/2.