Liquid phase assisted hot pressing of boron suboxide-materials

B6O composites were prepared by hot pressing of B6O powder with alumina, aluminium and carbon additions. Dense materials with hardness higher than 30 GPa and fracture toughness of 3 MPa m1/2 were achieved at 1900 °C. The sintering behaviour and the formed phases were discussed on the bases of thermodynamic calculations. The thermodynamic properties of boron suboxide (B6O) were approximated at high temperatures. The phase equilibria computed based on the obtained thermodynamic properties, agree with the available experimental data. The modelled thermodynamic properties of B6O have been applied to analyse interpretation of the sintering behaviour and the stability of these materials. The thermodynamic calculations and microstructural analysis showed that the densification takes place by liquid phase sintering.