Silicon nitride joining using rare-earth reaction sintering

Journal Article · Sat Feb 15 04:00:00 EST 1997 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(96)00392-2· OSTI ID:438629

Gopal, M; De Jonghe, L C; Thomas, G ^[1]

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1. Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

One of the key technological challenges to be overcome in order for ceramics to be used as high temperature structural materials is the ability to join it to other materials. A commonly used joining route is through an interlayer. In Si{sub 3}N{sub 4} ceramics, conventional sintering aids such as MgO, Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} have been widely used as the joint interlayers. While exhibiting good room temperature strength these soften rapidly at high temperatures, because at elevated temperatures (T > 1,000 C), the sintering aid forms a glassy silicate or oxynitride phase, promoting grain boundary sliding. The objective of the earlier work on Si{sub 3}N{sub 4} sintering was to use additives that would sinter via a liquid phase and would crystallize on cooling. The sintering agents that achieve these objectives were shown to be rare-earth oxides (Re{sub 2}O{sub 3}) and silica (SiO{sub 2}). During the sintering process, reaction occurs to form Re{sub 2}Si{sub 2}O{sub 7} as the intergranular phase. The advantage of this crystalline grain boundary phase is that it greatly reduces viscosity and intergranular creep. The material therefore retains 90% of its room temperature strength at high temperatures (T {approximately} 1,400 C).

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 438629
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 4 Vol. 36; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
INTERFACES
JOINING
OXIDES
RARE EARTHS
SILICON NITRIDES
SILICON OXIDES
SINTERING