SINTERING OF BETA-SI3N4 POWDER MADE BY TH E IMIDE-DECOMPOSITION METHOD

Beta-Si3N4 powder made by the imide-decomposition method was gas-press ure sintered at 1800 degrees C for 4h in 1 MPa N-2 gas. This material had a microstructure of ''in-situ composite'' and excellent mechanical properties (strength : 780 MPa, fracture toughness : 7.5 MPa . m(1/2) ), whereas beta-Si3N4 powder made by the silicon nitridation method re quired sintering temperatures higher than 1900 degrees C to attain sim ilar microstructure and mechanical properties. beta-Si3N4 powder by th e imide-decomposition method had excellent properties for grain growth at low temperatures.