Grain-boundary relaxation in high-purity silicon nitride

Journal Article · Sun Sep 01 04:00:00 EDT 1996 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1996.tb08968.x· OSTI ID:417732

Pezzotti, G ^[1]; Ota, Ken`ichi ^[2]; Kleebe, H J ^[3]

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1. Toyohashi Univ. of Technology (Japan). Dept. of Materials Science
2. Osaka Univ., Ibaraki, Osaka (Japan). Inst. of Scientific and Industrial Research
3. Univ. Bayreuth (Germany). Inst. fuer Materialforschung

Internal friction, torsional creep, and shear modulus relaxation experiments were conducted on a model Si{sub 3}N{sub 4} polycrystalline material, which contained a continuous amorphous film of pure SiO{sub 2} at the grain boundary. Internal friction experiments were performed in the frequency range between 3 and 13 Hz, in 5 Pa of nitrogen atmosphere. Very high temperatures (up to 2,000 C) could be applied for the first time by using a newly developed torsional pendulum apparatus. This apparatus was also capable of precise torsional strain measurements under static-load conditions. The internal friction curves at various frequencies were generally found to consist of a grain-boundary peak super-imposed on an exponential-like background. The peak, of anelastic diffusive origin, was centered in the temperature range of 1,612--1,710 C depending on the frequency of the measurement, namely within an interval of about 100 C below the nominal melting point of the pure SiO{sub 2} phase (i.e., {approx}1,730 C). The background was instead found to be of viscoelastic nature. A common micromechanical origin between the creep plastic strain and the internal friction background curves was identified and the data could be fitted by the same Arrhenius plot. Structural and chemical characterization of internal grain boundaries was performed by high-resolution electron microscopy (HREM) in addition to electron energy-loss spectroscopy (EELS). According to the above set of microstructural/chemical and mechanical data, the viscosity properties of the intergranular phase were assessed and the sliding mechanism between adjacent Si{sub 3}N{sub 4} grains was modeled.

• Sponsoring Organization: USDOE
• OSTI ID: 417732
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 9 Vol. 79; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMORPHOUS STATE
CREEP
ELECTRON MICROSCOPY
ENERGY-LOSS SPECTROSCOPY
GRAIN BOUNDARIES
INTERNAL FRICTION
MECHANICAL PROPERTIES
POLYCRYSTALS
SHEAR PROPERTIES
SILICON NITRIDES
SILICON OXIDES
STRAINS
TEMPERATURE DEPENDENCE
TORSION
VISCOSITY