The process of crystallization of gel and the luminescence of ions in gel-derived crystals

The process of crystallization of gel and the influence of crystallization on the luminescence of ions have been investigated. Differential thermal analysis and thermogravimetric analysis showed that residual solvents and organic compounds chemically bound to Ca and Si were eliminated for . The exothermic effect corresponding to crystallization of the gel appeared at about , and the activation energy of crystallization was about . With the increase of temperature, x-ray diffraction patterns indicated a transformation from rankinite to wollastonite structure. The excitation and emission intensities for ions in the gel-derived crystals were much stronger than those for the dried gel. The excitation and emission spectra of ions changed during the process of crystallization, and the obvious level splitting by the crystal field can be observed in both the rankinite and wollastonite structures.