Non-Isothermal Crystallization Kinetics of Transparent Glass-Ceramic Phosphors Containing Calcium Magnesium Aluminosilicate Nanocrystals

Glass-ceramic phosphors from CaO-MgO-SiO2-Al2O3-ZnO co-doped with 0.5Eu(3+):0.1Sm(3+) (mole%) were prepared by conventional melt-quenching method. Non-isothermal crystallization kinetics were performed by differential thermal analysis at various heating rates of 5, 10, 15 and 20 degrees C/min. The parent glasses were investigated by X-ray diffraction technique. From the heating rate dependence of crystallization temperature, the activation energy (E-a) of crystallization and Avrami parameter (n) were calculated by Kissinger equation and Ozawa equation, respectively. The results indicated that continuous nucleation and three-dimensional crystal growth were the dominating mechanisms in the crystallization process that was confirmed by scanning electronic microscopy and transmission electron microscopy. The luminescence properties were also determined by fluorescence spectroscopy in rang of 550-750 nm under 402 nm excitation. The results of XRD studies revealed the occurrence of diopside (Ca0.8Mg1.2Si2O6) phases and no other phase is observed. The emission spectra exhibited a strong red luminescence composed of 576, 599, 613 and 702 nm when excited at 402 nm.