Oxynitride glasses: Preparation, properties and implications for mechanical behaviour of silicon nitride

S. Hampshire, M. J. Pomeroy

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Oxynitride glasses are found at grain boundaries, i.e. triple point junctions and intergranular films, in silicon nitride based materials as a result of cooling of liquid phases formed by reaction of sintering additives with silicon nitride and silica present on the nitride surface during the densification of the ceramics. The glass chemistry, particularly the content of modifying cation, usually Y or a rare earth (RE) ion, and the volume fractions of these oxynitride glass phases within the ceramic affect the properties of silicon nitride such as fracture toughness and creep at high temperature. As nitrogen substitutes for oxygen in silicate and alumino-silicate glasses, increases are observed in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. If changes are made to the RE:Si:Al ratios or as the size of the rare earth cation decreases, properties such as viscosity can be increased by a further two to three orders of magnitude. These effects have a strong impact on the mechanical properties of silicon nitride based ceramics, especially creep resistance. This paper provides an overview of previous work on oxynitride glasses and outlines the effect of glass composition on their properties and discusses the implications for high temperature behaviour of Si 3N4 ceramics.

Original languageEnglish
Title of host publicationNitrides and Oxynitrides III - Proceedings of the 5th International Symposium on Nitrides
PublisherTrans Tech Publications Ltd
Pages11-16
Number of pages6
ISBN (Print)0878494391, 9780878494392
DOIs
Publication statusPublished - 2007
Event5th International Symposium on Nitrides - Eskisehir, Turkey
Duration: 3 Apr 20065 Apr 2006

Publication series

NameMaterials Science Forum
Volume554
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Conference

Conference5th International Symposium on Nitrides
Country/TerritoryTurkey
CityEskisehir
Period3/04/065/04/06

Keywords

  • Creep
  • Grain boundary
  • Oxynitride glass
  • SiAION glass
  • Silicon nitride
  • Viscosity

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