The effect of additives on sintering behavior and strength retention in silicon nitride with RE-disilicate

Z. L. Hong, H. Yoshida, Y. Ikuhara, T. Sakuma, T. Nishimura, M. Mitomo

    Research output: Contribution to journalArticle

    62 Citations (Scopus)

    Abstract

    Four kinds of Si3N4-RE2Si2O7 (RE:Nd, Sm, Y, Yb) ceramics have been fabricated by hot pressing at 1725-1750°C for 2 h in N2 gas flow and post-annealing at 1450°C for 4 h. The effect of rare-earth oxide additions on the densification process was investigated by measuring the shrinkage of the compact. Results revealed that the rare-earth oxides affect the densification process of Si3N4-RE2Si2O7 ceramics in which the shrinkage temperature varies with the types of rare-earth additives. The Si-RE-O-N liquid phase formation temperature can be estimated from the onset temperature of final shrinkage stage, and the temperature is in the order of Sm < Nd < Y < Yb. Flexural strength was examined at temperature in a range of 25-1600°C in N2 gas flow. The high temperature strength of Si3N4-Yb2Si2O7 or Si3N4-Y2Si2O7 ceramics is better than that of Si3N4-Sm2Si2O7 or Si3N4-Nd2Si2O7 ceramics. There is a roughly linear relation between the strength retention and the liquid phase formation temperature. Present results indicate that Si3N4-RE2Si2O7 ceramics with high strength retention can be fabricated by adopting additives with small ionic radius and high ionic charge.

    Original languageEnglish
    Pages (from-to)527-534
    Number of pages8
    JournalJournal of the European Ceramic Society
    Volume22
    Issue number4
    DOIs
    Publication statusPublished - 2002 Apr 1

    Keywords

    • Grain boundaries
    • Hot-pressing
    • Mechanical properties
    • SiN
    • Strength

    ASJC Scopus subject areas

    • Ceramics and Composites
    • Materials Chemistry

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