B6O materials with Al2O3/Y2O3 additives densified by FAST/SPS and HIP

Fully densified B6O materials with Al2O3/Y2O3 sintering additives amounts systematically varied between 0 and 15 vol.% and Al2O3/(Al2O3 + Y2O3) molar ratios of 0.05–1 were prepared by FAST/SPS and HIP at sintering temperatures between 1725 °C and 1900 °C. Their densification and microstructure were correlated with measured mechanical properties. The addition of low additive amounts in the range of 2–3 vol.% was found to increase the fracture toughness and strength from 2.0 MPa m1/2 (SEVNB) and 420 MPa for pure B6O to about 3.0 MPa m1/2 and 540 MPa, but it had no effect on the hardness, which remained at a high level of 30–36 GPa (HV0.4). Higher additive contents did not yield a further improvement in the toughness but resulted in a reduction in hardness and strength.