Crystallographic characterization of silicon nitride ceramics sintered with Y2O3-Al2O3 or E2O3-Al2O3 additions

Silicon nitride ceramics were sintered using Y2O3-Al2O3 or E2O3-Al2O3 (E2O3 denotes a mixed oxide Of Y2O3 and rare-earth oxides) as sintering additives. The intergranular phases formed after sintering was investigated using high-resolution X-ray diffraction (HRXRD). The use of synchrotron radiation enabled high angular resolution and a high signal to background ratio. Besides the appearance Of beta-Si3N4 phase the intergranular phases Y3Al5O12 (YAG) and Y2SiO5 were identified in both samples. The refinement of the structural parameters by the Rietveld method indicated similar crystalline structure Of beta-Si3N4 for both systems used as sintering additive. On the other hand, the intergranular phases Y3Al5O12 and Y2SiO5 shown a decrease of the lattice parameters, when E2O3 was used as additive, indicating the formation of solid solutions of E3Al5O12 and E2SiO5, respectively. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.