Microhardness Load/Size Effect in Individual Grains of a Gas Pressure Sintered Silicon Nitride.

Vickers microhardness as a function of the indentation load and of grain orientation was studied in individual grains of a gas pressure sintered polycrystalline silicon nitride using indentation loads in the range from 1g to 50 g. The microhardness values are lower than the microhardness of Beta - Si3N4 single crystals, which is probably caused by softening of the silicon nitride lattice by the presence of oxygen and aluminium atoms. The indentation load size effect (ISE) was more evident in the prismatic planes of the grains. The threshold load for indent formation is below 1g for both basal and prismatic planes of Si3n4 grains in the studied GPS silicon nitride.JRC.(IAM)-Institute For Advanced Material