Fabrication and secondary-phase crystallization of rare-earth disilicate-silicon nitride ceramics

Journal Article · Sat Aug 01 00:00:00 EDT 1992 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1992.tb04462.x· OSTI ID:7018764

Cinibulk, M K; Thomas, G ^[1]; Johnson, S M ^[2]

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1. Lawrence Berkeley Lab., CA (United States). Center for Advanced Materials
2. SRI International, Menlo Park, CA (United States). Materials Research Lab.

In this paper, the fabrication and intergranular-phase devitrification of silicon nitride densified with rare-earth (RE) oxide additives is investigated. The additions of the oxides of Sm, Gd, Dy, Er, and Yb, having high melting points and behaving similarly to Y[sub 2]O[sub 3], were compositionally controlled to tailor a microstructure with a crystalline secondary phase of RE[sub 2]Si[sub 2]O[sub 7]. The lanthanide oxides were found to be ass effective as Y[sub 2]O[sub 3] in densifying Si[sub 3]N[sub 4], resulting in identical microstructures and densities of 98-99% of theoretical density. The crystallization behavior of all six disilicates was similar, characterized by a limited nucleation and rapid growth mechanism resulting in large single crystals. Complete crystallization of the intergranular phase was obtained with the exception of a thin residual amorphous film which was observed at interfaces and believed to be rich in impurities, the cause of incomplete devitrification.

• Sponsoring Organization: National Science Foundation (NSF); National Science Foundation, Washington, DC (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 7018764
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 75:8; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
SILICON NITRIDES
FABRICATION
PHASE TRANSFORMATIONS
ADDITIVES
DENSITY
DYSPROSIUM OXIDES
ERBIUM OXIDES
GADOLINIUM OXIDES
IMPURITIES
INTERGRANULAR CORROSION
MICROSTRUCTURE
PROCESS CONTROL
RARE EARTH COMPOUNDS
YTTERBIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CONTROL
CORROSION
CRYSTAL STRUCTURE
DYSPROSIUM COMPOUNDS
ERBIUM COMPOUNDS
GADOLINIUM COMPOUNDS
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PNICTIDES
SILICON COMPOUNDS
YTTERBIUM COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360201 - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360204 - Ceramics
Cermets
& Refractories- Physical Properties