Synthesis of Si3N4-Based Powder Composites for Ceramic Fabrication by Spark Plasma Sintering

There were examined four ways of applying sintering additives (Y2O3 : Al2O3 = 3 : 5) to particles of commercial Si3N4 powders differing in particle size composition: amorphous nanopowder and microcrystalline alpha-Si3N4 powder. The oxide sintering additive coating was produced in two steps: wet chemical preparation of the starting Si3N4 powder with compounds containing yttrium and aluminum ions and annealing of the resultant powder composites at a temperature of 1000 degrees C in air. The way the sintering addition is applied and the particle size composition of the starting Si3N4 powder have been shown to influence the composition of the crystalline phases forming during annealing. The optimal process for obtaining Si3N4 ceramics with improved physical and mechanical properties is spray drying, which makes it possible to obtain spherical agglomerates.