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Application of the IR transmission method and the Mossbauer effect to the crystallization of calcium gallate glass
- Crystallization of infrared-light transmitting 40CaO·60Ga2O3 glass caused by heat treatment, Full-size image (<1 K)γ-ray irradiation and YAG laser irradiation was investigated. The X-ray diffraction (XRD) data revealed that a CaGa4O7 phase was precipitated by heat treatment. The Avrami index (n) of 1.7±0.2 obtained from `the Fourier transform infrared (FT-IR) transmission method' combined with the Johnson–Mehl–Avrami (JMA) equation indicated that the crystallization proceeded three dimensionally. The activation energy (Ea) of 7.2±0.3 eV obtained from the JMA plot was equal to that obtained from the Kissinger plot in the differential thermal analysis: Ea=7.1±0.2 eV. Mössbauer spectra of 40CaO·59Ga2O3·Full-size image (<1 K)2O3 samples showed the oxidation of iron from Fe2+ to Fe3+. Mössbauer spectra of the 40CaO·59Ga2O3·Full-size image (<1 K)2O3 samples irradiated with the YAG laser also showed an oxidation of Fe2+ to Fe3+. In case of Full-size image (<1 K)γ-ray irradiated samples, however, a reduction of the iron from Fe3+ to Fe2+ was observed. This result indicates that Fe3+ occupies substitutional sites of Ga3+ in the gallate glass.