Nucleation stable crystalline product

If this phase transformation is a sequential process where even crystalline phases are transformed to other crystalline phases, characteristic changes observable in the stability range (D) of phase I must correspond to the incubation period (BO for the second crystalline phase (II), where the nucleation of the subsequent product takes place. As a consequence, the recrystallization process (period E) of phase I and the growing period (CO of phase II are of the same time scale. This sequential recrystallization process finally leads to thermodynamically more stable products such as cristobalite and quartz. 

Stoichiometry has long been used by solid-state chemists to control the final products of a reaction. However, traditional synthetic techniques do not have the ability to control reaction intermediates and all stable phases will form as illustrated in Figure 2. For example, in the iron-silicon system, thin film diffusion couples have been used to determine the sequence of phase formation (79). FeSi was always found to nucleate first, followed by the crystallization of FeSi2 at the FeSi-Si interface and FeSi3 at the FeSi-Fe interface. The following paragraphs provide evidence that stoichiometry of the amorphous intermediates can be used to control nucleation to obtain the desired crystalline compounds directly. Thus, we use stoichiometry to control the mechanism of the reaction. 

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