Crystallization Process Of Glass Research Articles

Liquid-phase separation in glass-forming systems

This review is concerned with the process of liquid-phase separation in glass-forming systems. In the first part a general account of phase equilibria is presented together with a discussion of the thermodynamic behaviour of systems exhibiting liquid-liquid immiscibility. The estimation of free energies from phase-boundary data and the location of the spinodal boundary are briefly considered. The origin of immiscibility in silicate solutions is discussed from a thermodynamic approach. The importance of association, particularly in silicate systems, is stressed. In the second part of the review, an outline of the theories of homogeneous nucleation and spinodal decomposition is given and a review of recent theoretical developments. The intersecting growth model is discussed and also the laterstage coarsening of both droplet and interconnected structures. The theories are compared with experimental results (including electron microscope and small-angle X-ray scattering data) for various systems. The effects of phase separation on crystallization processes in glasses and on the physical and chemical properties of glasses are outlined. Although the results considered are for oxide systems where sufficient data are available, much of the discussion is applicable to glass-forming systems in general.

Phase transformation in the oxides

This paper reviews phase transformations in the oxides, and briefly examines the similarities and dissimilarities with the phase transitions in metals. A few topics selected for the discussion, include, displacive phase transitions, order-disorder transitions, and clustering and precipitation. The displacive transition involves the oxygen polyhedra, and is usually found in ferroelectric and antiferroelectric oxides, such as, BaTiO3, SrTiO3, PbZrO3, and other oxides of perovskite structure. In lattice dynamics studies, this transition has been associated with an instability of a long-wave optical phonon. The condensation of the ferroelectric soft mode causes the static distortion of the lattice at the phase transition. The order-disorder transformation in the oxides may occur in different forms. It may be the hydrogen ordering in KDP, the catio distributions in spinel MgFe2O4,the Li-Fe ordering of the octahedral sites in LiFe5O8, or the formations of layer structures in the double perovskites, such as Ba2CoWO6, Ba2CoReO6, and others. Clustering and precipitations are commonly observed phenomena in oxide systems. They result in phase separations in both the crystalline, and the glassy systems. Heat treatments to control the crystallization processes in glasses result in glass ceramics, which have been proven to be superior to both the original glass, and to the precipitated crystalline phase.

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Phase Separation and Crystallization Process in Glasses

Phase Separation and Crystallization Process in Glasses

Effect of modifying additives on the crystallization process in glass

Effect of modifying additives on the crystallization process in glass