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Phase transitions in vitreous and amorphous SiO 1
Author(s) -
Gerber Th.,
Himmel B.,
Lorenz H.,
Stachel D.
Publication year - 1988
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.2170231018
Subject(s) - cristobalite , amorphous solid , materials science , crystallization , phase transition , polyamorphism , glass transition , diffraction , topology (electrical circuits) , phase (matter) , quartz , crystallography , amorphous silica , chemical engineering , composite material , optics , chemistry , thermodynamics , polymer , organic chemistry , physics , mathematics , combinatorics , engineering
Abstract As a rule, glassy and amorphous solids are characterized by random, irregular structures. More recent examinations, however, indicated that even this group of materials possesses certain structural laws. Glassy and amorphous SiO 2 samples were investigated using X‐ray diffraction. The results of this investigation can be interpreted as structural phase transitions. When subjected to a pressure‐temperature treatment ( p = 7 GPa, T = 700 °C), a 15 per cent irreversible densification of vitreous silica without crystallization could be achieved. This can be interpreted as a reconstructive transformation of a certain topological structure (vitreous silica having a cristobalite topology) into another topological structure (densified vitreous silica having a quartz topology). Temperature‐dependent measurements of disperse SiO 2 (porous glass, silica gels) led to the conclusion that a displacive phase transition (analogous to the α‐β‐transition in cristobalite) had taken place in the amorphous network.