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Internal and platinum initiated crystallization in Na 2 O.2 CaO. 3 SiO 2 glasses: early stages of growth
Author(s) -
GonzalezOliver C. J. R.,
James P. F.
Publication year - 1980
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1980.tb04078.x
Subject(s) - nucleation , crystallization , transmission electron microscopy , platinum , materials science , crystallography , phase (matter) , diffraction , crystal growth , analytical chemistry (journal) , electron diffraction , chemistry , optics , nanotechnology , biochemistry , physics , organic chemistry , chromatography , catalysis
SUMMARY Transmission electron microscopy at 100, 900 and 1000 kV was used to study the early stages of growth of internally nucleated crystals of the phase Na 2 O.2 CaO. 3 SiO 2 (‘NC 2 S 3 ’) in glasses close to the NC 2 S 3 composition. Glass samples were partially crystallized by heat treatment in the range 833–873 K and thin foils for electron microscopy were prepared by ion beam thinning. The phase identified by electron diffraction from a number of small crystals (the low temperature form of NC 2 S 3 ) was the same as that determined by X‐ray diffraction of fully crystallized glass ceramics. Selected area diffraction and bright and dark field microscopy showed that in the early stages of development the crystallization centres were essentially single crystals but contained a significant concentration of defects. These crystals were nucleated, probably homogeneously, at temperatures higher than the well‐established low to high reversible polymorphic transformation of the NC 2 S 3 crystalline phase. In a glass of similar composition to which platinum was deliberately added there was clear evidence for heterogeneous nucleation of NC 2 S 3 crystals on platinum particles distributed in the glass. Also the contact angle between NC 2 S 3 crystals and the rounded platinum particles could be measured directly.