ELECTRON-PROBE MICROANALYSIS OF CHEMICAL GRADIENTS IN GAS-PRESSURE SINTERED SILICON-NITRIDE

During gas pressure sintering of silicon nitride (Si3N4) - which norma lly contains oxide additives such as SiO2, Al2O3 and Y2O3 - in a resis tance heated graphite furnace, a reduction of the Si3N4, sample takes place. At high temperatures (> 1800-degrees-C) this effect is accompan ied by decomposition reactions of Si3N4. Both lead to chemical gradien ts in larger components which influence the strength of the sintered a rticle. Electron probe microanalysis (EPMA) has been carried out in or der to study the influence of the crucible material [graphite (C), bor on nitride (BN)] and the quantity of filling on the gradient formation .