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Lookup NU author(s): Emeritus Professor Derek Thompson
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Two phase α/β and single phase α lithium sialons with different m and n values were produced by hot pressing at 1730-1750 °C at 30 MPa for 30-40 min in a graphite resistance furnace. When the two-phase samples were heat-treated at lower (1200-1450 °C) temperatures in different packing powders, an increase in the amount of α was observed, due to β-sialon in the as-sintered material reacting with grain boundary liquid to form more α. β→α transformation at low temperatures has not been reported previously in any sialon system and in the present case is believed to occur because the α-sialon phase field in the lithium sialon system shifts slightly towards the β-sialon line at lower temperatures. The thermal stability of lithium α-sialon is good in the centre of the single-phase α region when surrounded by a Li-containing powder bed. However, towards the edges of the single-phase region, compositional changes occur on heat-treatment. Thus, samples with high m, n values decompose into β-sialon plus other Li-containing phases. During heat-treatment of other compositions when surrounded by a BN powder bed, the composition of the α-sialon phase continually readjusts towards the α/β sialon phase region as a function of time and this is followed by decomposition of the α phase. Evaporation of the Li+ stabilizing cation is believed to be the main reason for this behaviour. The effects of m and n value, heat treatment parameters and packing powder on the thermal stability of Li α-sialons are discussed.
Author(s): Yu ZB, Thompson DP, Bhatti AR
Publication type: Article
Publication status: Published
Journal: Journal of the European Ceramic Society
Year: 2000
Volume: 20
Issue: 11
Pages: 1815-1828
ISSN (print): 0955-2219
ISSN (electronic): 1873-619X
Publisher: Elsevier
URL: http://dx.doi.org/10.1016/S0955-2219(00)00044-3
DOI: 10.1016/S0955-2219(00)00044-3
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