An
in-situ observation method has been developed to observe growth or dissolution processes of crystals at <1800 K, with as high visibility as in air, and under precisely controlled conditions. The method has been applied to silicate systems. Out of varieties of interesting phenomena, observations on metastable nucleation, which often takes place in complex component systems, are selected for this article. It is shown in a variety of silicate systems that a thermodynamically less stable phase can nucleate and grow steadily prior to the nucleation of the stable phase. This metastable nucleation is interpreted in terms of competition between the difference of interfacial energy between a crystal and a solution, which is evaluated by the number of unsaturated dangling bonds at the crystal surface, and chemical potential of the solution, which is evaluated from the solubility curve determined by this method.
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