Effect of Al metal precursor on the phase formation and mechanical properties of fine-grained SiAlON ceramics prepared by spark plasma sintering

This paper reports the effects of using nano-precursor powders, including α-Si₃N₄ or amorphous-Si₃N₄, and particularly the partial replacement of AlN by Al metal precursor, on the properties of a fixed Ca-α-SiAlON composition, consolidated by spark plasma sintering at 1450 °C and 1600 °C. The observed changes in mechanical properties are related to the phases present in the microstructures. In addition to allowing the consolidation of dense and fine ceramics at lower temperatures, the partial replacement of AlN by Al metal precursor has shown remarkable improvement in the mechanical properties of samples sintered at 1600 °C containing α-Si₃N₄, a result of fine α-SiAlON grains and nitrogen-rich grain boundary phase. Another key contribution of Al metal precursor is found in lowering the sintering temperature while keeping, or even improving, the mechanical properties of the sintered samples, as observed in samples sintered at 1450 °C.