Compressive creep behavior of hot-pressed Si{sub 3}N{sub 4}-CRE{sub 2}O{sub 3}-Al{sub 2}O{sub 3} ceramics
In this work, yttrium-rare earth oxide solid solution, CRE{sub 2}O{sub 3}, produced at FAENQUIL-DEMAR at a cost of only 20% of pure commercial Y{sub 2}O{sub 3}, was used as sintering additive of hot-pressed Si{sub 3}N{sub 4} ceramics. The objective of this work was to characterize and to investigate the creep behavior of these ceramics. The samples were sintered by hot-pressing at 1750 deg. C, for 30 min using a pressure of 20 MPa. Compressive creep tests were carried out in air, between 1250 and 1300 deg. C, for 60 h, under stresses of 200-300 MPa. The stress exponent under all conditions was determined to be about unity. The apparent activation energy obtained was around 460 kJ mol{sup -1}, corresponding to the heat of solution of the Si{sub 3}N{sub 4} in the glassy phase. Both the stress exponent n and apparent activation energy Q are within the range of values reported in other studies of the compressive creep of Y{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-doped-Si{sub 3}N{sub 4} ceramics. X-ray diffraction (XRD) characterization shows a global reorientation of the {beta}-Si{sub 3}N{sub 4} grains and SEM observations detected no grain growth after the creep tests. These results indicate that grain-boundary sliding controlled by viscous flow is the dominant creep mechanism observed in the present study. The creep resistance presented of this samples indicates that this additive CRE{sub 2}O{sub 3} can be a cheap alternative in the fabrication of Si{sub 3}N{sub 4} ceramics, resulting in promising mechanical properties.
- OSTI ID:
- 20883081
- Journal Information:
- Materials Research Bulletin, Vol. 39, Issue 9; Other Information: DOI: 10.1016/j.materresbull.2004.04.006; PII: S0025540804000960; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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