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Growth‐Sector Boundaries and Growth‐Rate Dispersion in Potassium Alum Crystals
Author(s) -
Klapper H.,
Becker R. A.,
Schmiemann D.,
Faber A.
Publication year - 2002
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 - 10.1002/1521-4079(200207)37:7<747::aid-crat747>3.0.co;2-2
Subject(s) - dissolution , growth rate , crystallography , materials science , crystal growth , dispersion (optics) , crystal (programming language) , potassium , alum , mineralogy , chemistry , chemical physics , optics , geometry , metallurgy , physics , mathematics , programming language , computer science
Crystals of potassium alum, pure and slightly doped with Cr 3+ , were grown from aqueous solution by slow temperature lowering. In addition, short re‐dissolution periods were introduced in order to provoke growth defects and changes of growth rates. Crystal slices of about 1 mm thickness were studied by conventional LANG X‐ray diffraction topography using MoKα radiation. For Cr‐doped crystals, boundaries between {100}, {100} and {111} growth sectors appear by pronounced dynamical X‐ray topographic contrast similar to that of stacking faults. Re‐dissolution experiments provoke the formation of inclusions on {100} faces, followed by an increase of the {100} growth rate by the factor of about six, relative to the neighboured {111} faces. X‐ray topographs show that this increase is correlated with the formation of dislocations, which interestingly have pure‐edge character. During further growth these dislocations penetrate the {100}‐{111} growth sector boundary and vanish from the {100} face, which slows down and finally adopts its former growth rate before re‐dissolution.