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α ↔ βtransformation ïn lithium a-sialon ceramics

Lookup NU author(s): Zhengbo Yu

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Abstract

The phenomenon of cc<=>β transformation in sialon ceramics was originally demonstrated in yttrium and rare earth systems, where a-sialons prepared at high (1700-1800°C) sintering temperatures were found to be unstable with respect to β-sialon plus additional crystalline or vitreous phases when heat-treated at lower (1200-1600°C) temperatures. Lithium a-sialons show significant differences compared with trivalent cation stabilised equivalents (a) in allowing both of the interstitial sites in the unit cell to be completely filled with lithium atoms, and (b) in forming at values of x in the a-sialon formula (LixSi12.m-nAlm+nOnN16.n) significantly lower than for divalent and trivalent cations. Moreover, low m-value a-sialon compositions display β->a sialon transformation when heat-treated at low (1200-1400°C) temperatures, in contrast to the behaviour observed in higher-valent a-sialons. These results are discussed in the light of current ideas on the mechanism of a<=>β transformation in terms of transformation temperature and phase relationships. ©2000 Trans Tech Publications,.


Publication metadata

Author(s): Yu ZB, Thompson OP

Publication type: Article

Publication status: Published

Journal: Materials Science Forum

Year: 2000

Volume: 325-326

Pages: 185-190

Print publication date: 01/01/2000

ISSN (print): 0255-5476

ISSN (electronic):

Publisher: Trans Tech Publications

URL: http://dx.doi.org/10.4028/www.scientific.net/MSF.325-326.185

DOI: 10.4028/www.scientific.net/MSF.325-326.185


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