In this study, α-Si3N4 ceramics were successfully prepared using MgO and AlPO4 as the sintering additives and a low temperature spark plasma sintering (SPS) technique. The resultant α-Si3N4 ceramics sintered from 1300 oC to 1500 oC show a fine microstructure with nearly no grain growth and phase transformation. The dielectric properties of the sintered ceramics are investigated in detail. α-Si3N4 ceramics with a porosity of 5-36% show a dielectric constant of 4.5-7.4 and a dielectric loss of less than 10 × 10−3. The existence of AlPO4 performing as a binder not only contributes to the low temperature sintering of fully-dense α-Si3N4 ceramics, but also reduces the dielectric constant and loss.
Keywords: Silicon nitride, Spark plasma sintering (SPS), Phosphate, Dielectric prosperities.