New silicon nitride material has a high silicon dioxide content, a sub-micron grain size and a low defect content

摘要

A new silicon nitride material has a high silicon dioxide content, a sub-micron grain size and a low defect content. A silicon nitride material has, in the sintered condition, a molar ratio of silicon dioxide to the sum of the silicon dioxide and other sintering additives of greater than 50 %, a mean particle size of = 0.3 mu and a content of = 5000/mm2 of defects with a maximum linear dimension of greater than 3 mu . An Independent claim is also included for production of the above silicon nitride material, in which the Si3N4 powder is thermally oxidized alone or together with sintering additives, mixed with finely dispersed SiO2 powder, subjected to intensive grinding, alone or together with sintering additives and/or mixed with a material containing a SiO2-forming component before or during grinding, followed by sintering, pressure sintering, hot pressing or hot isostatic pressing.