UNSPECIFIED (1999) Crystal nucleation in P2O5-doped lithium disilicate glasses. JOURNAL OF MATERIALS SCIENCE, 34 (18). pp. 4399-4411. ISSN 0022-2461

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Abstract

The bulk (volume) crystallisation of Li2O . 2SiO(2) (LS2) glasses with additions of 1, 2 and 5 mol % P2O5 (G1P, G2P and G5P) was investigated. In the G1P and G2P glasses heated at 454 degrees C metastable alpha'- and beta'-LS2 crystal phases formed initially and only stable LS2 at later stages. In G1P heated at 463 degrees C transmission electron microscopy (TEM) revealed particles (greater than or equal to 2 mu m) of stable LS2 but also smaller (< 0.1 mu m) crystalline particles which were unstable under the electron beam and could not be identified. Crystalline lithium orthophosphate (Li3PO4) was detected by XRD and P-31 magic angle spinning nuclear magnetic resonance (MAS-NMR) in both as-quenched and heat treated G5P but not in G1P and G2P. In G5P heated at 476 degrees C, metastable alpha'-LS2 phase initially formed and at later times stable LS2. In as-quenched G5P, a trace of lithium metasilicate (LS) was observed. Li3PO4 crystals were not detected in G5P by TEM but a marked increase in nucleation rate due to P2O5 addition was observed. Si-29 MAS-NMR revealed amorphous Q(2) (LS) and Q(4) (SiO2) species in an average Q(3) (LS2) environment in the as-quenched glasses. Increased P2O5 concentration caused a greater degree of amorphous phase separation. (3)1P MAS-NMR showed amorphous lithium phosphate units in the as-quenched and nucleated G1P and G2P. The presence of crystalline Li3PO4 phase in glass G5P suggests that Li3PO4 crystals may act as sites for heterogeneous nucleation of stable lithium disilicate. (C) 1999 Kluwer Academic Publishers.

Item Type:	Journal Article
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Journal or Publication Title:	JOURNAL OF MATERIALS SCIENCE
Publisher:	KLUWER ACADEMIC PUBL
ISSN:	0022-2461
Date:	1999
Volume:	34
Number:	18
Number of Pages:	13
Page Range:	pp. 4399-4411
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/14250

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