The Research on High Pressure Sintering of Mixed Powder γ-Si3N4 and α-Si3N4
The high pressure and high temperature sintering of α-Si3N4 and γ-Si3N4 with Y2O3-Al2O3-La2O3 as additives were studied under pressures of 5.4 GPa and temperatures of 1420-1770 K. The effects of sintering temperatures and pressures on properties of sintered ceramic samples were investigated with X-ray diffraction and scanning electron microscopy. The results show that γ-Si3N4 and α-Si3N4 is transformed to β-Si3N4 completely. The highest relative densities and Vickers hardness (HV) of sintered samples are 98.71 and 21.76GPa, respectively. The sintered samples were composed of elongated β-Si3N4 rod crystals with disordered orientation and had intergranular interlocks and uniform and compact microstructure. Pulled out crystal grains on the fractured cross sections were obviously observed by SEM.
Xiaoming Sang, Pengcheng Wang, Liqun Ai, Yungang Li and Jinglong Bu
H. Yao et al., "The Research on High Pressure Sintering of Mixed Powder γ-Si3N4 and α-Si3N4", Advanced Materials Research, Vols. 284-286, pp. 1397-1400, 2011