Boron suboxide materials with rare-earth metal oxide additives

The basis of this study is that the mechanical properties of Boron suboxide (B₆O) materials, especially fracture toughness are greatly influenced by the composition of the grain boundary phase and the grain size of the phases in the sintered material. Therefore, in this work, effort has been directed towards improving the fracture toughness and densification of this material by incorporating potential rareearth oxide phases and tailoring the microstructure to the desired properties. Boron suboxide (B₆O) powder was synthesized from the reaction of amorphous boron and boric acid powders. The powder was hot pressed at 1900 °C and 50 MPa. Additionally to pure sintered B₆O, materials with rareearth oxides were prepared at 1850°C. The microstructure, phase composition and properties were investigated. More than 95% of the theoretical density was attained and fracture toughness up to 5.6±0.2 MPam^1/2was obtained for the materials. Although the pure B₆O sample was brittle, fracture toughness was strongly improved in the materials.