Low Temperature Sintering of Silicon Nitride Ceramics by Spark Plasma Sintering Technique

The α-Si3N4 matrix ceramics were prepared by spark plasma sintering using MgO–Al2O3 and MgO–AlPO4 as the sintering additives,respectively.The phase composition and microstructure of the samples were analyzed by X-ray diffraction and scanning electron microscope.The effects of sintering additives and sintering temperature on the relative density and mechanical properties of the samples were investigated.The results show that when 4%(in mass,the same below) MgO–4%Al2O3 were used as the sintering additives,the relative density and bending strength of the sample sintered at 1 400 ℃ reach 81% and 182 MPa,respectively,and the relative density and bending strength of the samples reduce with the increase of Al2O3 content in the sintering additive.When 4%MgO–16%AlPO4 were used as the sintering additives,the relative density and bending strength of the sample sintered at 1 300 ℃ reach 96% and 366.5 MPa,respectively,and the relative density and bending strength of the samples increase with the rise of sintering temperature.It indicates that the MgO–AlPO4 as sintering additives play a significant role in the low temperature sintering of Si3N4 ceramics,and not only reduce the sintering temperature but also improve the mechanical property of the sintered Si3N4 ceramics.