On the width of internal friction peak in ceramic polycrystals with intergranular glassy film

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

DOI:https://doi.org/10.1016/S1359-6462(96)00402-2· OSTI ID:438633

Pezzotti, G ^[1]; Ota, Ken`ichi ^[2]

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1. Kyoto Inst. of Tech., Sakyo, Kyoto (Japan). Dept. of Materials
2. Osaka Univ., Ibaraki, Osaka (Japan). Inst. of Scientific and Industrial Research

In the internal friction behavior of a wide range of ceramic polycrystals there is a well detectable peak appearing at relatively high temperature, which reflects the occurrence of anelastic sliding at grain boundaries. Although this peak has been noticed also in some directly bonded ceramic polycrystals (e.,g., high-purity Al{sub 2}O{sub 3}), it best appears when a continuous glassy film encompasses the grains as, for example, in Si{sub 3}N{sub 4} ceramics. Basic viscoelasticity equations then may allow one to calculate the viscosity of the glassy film from the knowledge of both the temperature at which the peak-top manifests and the frequency of internal friction measurement. Another approach consists of systematically lowering the inherent viscosity of the glassy film with intentional additions of increasing amounts of suitable dopant. Thus, the temperature shift of the peak can be monitored at a fixed frequency. Also in this latter experiment the goal is to compare the grain-boundary viscosity value, as derived from internal friction experiments, to the viscosity value determined by macroscopic measurements on bulk glass of the same composition. Particularly effective is the comparison of the scaling viscosity (i.e., owing to increasing dopant addition) between film and bulk glass. Dealing with the latter experimental approach, the purpose of this short note is to relate the morphology of the internal friction peak in Si{sub 3}N{sub 4} ceramics with the type and amount of added dopant.

• OSTI ID: 438633
• 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
DOPED MATERIALS
GRAIN BOUNDARIES
INTERNAL FRICTION
MATERIALS TESTING
POLYCRYSTALS
SILICON NITRIDES
VISCOSITY