Effects of BN on the microstructural evolution and mechanical properties of BAS-BN composites

BAS-BN ceramic composites were synthesized by hot-press sintering at 1500 °C with various BN doping contents of 10–50 wt%. The influences of BN on the phase composition, microstructure and mechanical properties of the composite ceramics were studied. Results showed that the addition of BN significantly affected the hexagonal → monoclinic phase transformation of BAS. Single celsian was noted at BN content of 10 wt%, while a mixture of hexacelsian, celsian and some amorphous phase was obtained as BN additions beyond 20 wt%. With the increase in BN contents, nearly a fully dense composite was obtained when the BN content was lower than 30 wt%. And the mechanical performance of the composites was significantly improved. For ceramics with an addition of 30 wt% BN, the flexural strength and fracture toughness reached the maximum values, which was 193.5 MPa and 2.57 MPa m^1/2, respectively. And the bending strength is more than twice higher than that of pure BAS ceramic.