FORMS OF SOLID SOLUTION ORDERING UPON DECREASING TEMPERATURE
S. K. Filatov1, A. P. Shablinskii1,2, S. N. Volkov2, R. S. Bubnova1,2
1St. Petersburg State University, St. Petersburg, Russia
2Institute of Chemistry of Silicates, Russian Academy of Sciences, St. Petersburg, Russia
Keywords: кристаллохимия, твердый раствор, порядок-беспорядок, расщепление позиций, сверхструктуры, модулированные структуры, тепловое движение атомов, ротационно-кристаллические состояния, crystal chemistry, solid solution, order-disorder, splitting of sites, superstructures, modulated structures, thermal atomic motion, rotational crystalline states
Abstract
The work reports different forms of solid solution ordering: from the well-known atom redistribution processes over positions and the decomposition of the solid solution to the formation of superstructures, modulated structures, rotation of atomic groups, splitting of sites. For each ordering form as a crystal chemical phenomenon the position of atoms, molecules, and vacancies in the crystal structure of the solid solution is considered and the place of these processes among the main crystal chemical phenomena is determined. The manifestation of order-disorder processes in phase diagrams of systems is also analyzed: from the classical heterogeneous decomposition of solid solutions to the formation of ordered chemical compounds and other phase transitions. The necessity of a thorough study of the atomic-molecular nature of the solid solution ordering by modern X-ray diffraction crystallographic methods and high-resolution electron microscopy is demonstrated. For each ordering form examples are given, the driving force of the process is distinguished, and a brief literature review is presented.
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