Synthesis, sintering and characterisation of TaON materials

Theoretical investigations predict that TaON is likely to possess a relatively high hardness, thus making it a candidate for application as an abrasive or cutting tool material [J.E. Lowther, Theoretical study of potential high pressure phases of TaON and quaternary ZrTaO3N, in press]. TaON powder was produced by nitridation of amorphousTa2O5 powder in flowing ammonia in the 700–900 °C temperature range and an ammonia flow rate range of 40–50 cm3/min. The resulting powders were characterised in oxidation resistance by thermo-gravimetric analysis (TGA), phase purity by X-ray diffraction (XRD) and surface area by the BET method. The materials were densified under pressure using a belt type high pressure apparatus at 3–5.5 GPa in the temperature range of 920–1200 °C. The sintered samples were characterised in phase purity, Vickers macro-hardness and fracture toughness.