Energetical role of modeled intergranular glassy film in Si3N4-SiO2 ceramics

We have performed theoretical calculations to clarify the energetical role of an intergranular glassy film (IGF) by a static energy minimization techn ique using pair-potentials. A model structure of the IGF composed of silico n oxynitride (SON) is employed, which is consistent with the experimental e lectron energy-loss near-edge structure (ELNES). Two sets of calculations, i.e., for 0 degrees- and 180 degrees -twist boundaries, are done for Si3N4/ SON/Si3N4 and Si3N4/Si3N4 interfaces. It is found that the presence of SON at the 180 degrees -twist grain boundary is energetically favorable. The SO N phase plays an important role in relieving the strain energy at the grain boundary. The dependence of the interface energy on composition of the SON phase is also discussed. (C) 2000 Acta Metallurgica Inc. Published by Else vier Science Ltd. All rights reserved.