Boron suboxide materials with Co sintering additives

Difficulties in the densification as well as the low fracture toughness of the resulting polycrystalline materials have delayed the application of boron suboxide as a superhard material in industry. In this work, efforts have been made to improve the fracture toughness and densification of these materials by incorporating suitable secondary phases. Possible candidates are transition metals, which form under sintering conditions a liquid phase. Therefore different Co containing additives (metal, oxide and boride) were used to densify boron suboxide powder by hot pressing. The resulting materials have a significantly improved fracture toughness (3.9 MPa m1/2) and still high hardness (HV5 = 28.6 GPa.).