Comparison of plasma-chemical synthesised SiAlON nano-powder and conventional prepared SiAlON powder

Different mixtures of starting powders have been prepared to obtain a bulk material with an α+β-SiAlON phase composition according to the general formula for α-SiAlON: MexSi12−(m+n)Alm+nOnN16-n; Me=Y; v=valency of the Me, where m=0.51; n=1.0; x=m/v=0.17. This composition was derived from two different starting powders. One composition is based on powder mixture with a commercial available α-Si3N4 powder (Ube grade SN-E10) and additives (Y2O3, Al2O3 and AlN) produced by a conventional powder mixture process. The second powder was produced by a plasma-chemical synthesis. Both mixtures have the same ratio of oxides and nitrides. The compositions have been pressureless sintered under nitrogen atmosphere up to 1650 °C with a heating rate of 15 °C/min and a dwell time of 2 h. Data have been recorded and evaluated for the temperature range 1000–1650 °C. The relationship between density, phase composition, microstructure, and mechanical properties (hardness and fracture toughness) at different sintering temperatures were discussed.