Formation and spectral probing of transparent oxyfluoride glass-ceramics containing (Eu2+, Eu3+:BaGdF5) nano-crystals

In the present study, we report the formation of transparent glass-ceramics containing BaGdF5 nanocrystals under optimum ceramization of SiO2-BaF2-K2O-Sb2O3-GdF3--Eu2O3 based oxyfluoride glass and the energy transfer mechanisms in Eu2+ -> Eu3+ and Gd3+ -> Eu3+ has been interpreted through luminescence study. The modification of local environment surrounding dopant ion in glass and glass ceramics has been studied using Eu3+ ion as spectral probe. The optimum ceramization temperature was determined from the differential scanning calorimetry (DSC) thermogram which revealed that the glass transition temperature (T-g), the crystallization onset temperature (T-x), and crystallization peak temperature (T-p) are 563 degrees C, 607 degrees C and 641 degrees C, respectively. X-ray diffraction pattern of the glass-ceramics sample displayed the presence of cubic BaGdF5 phase (JCPDS code: 24-0098). Transmission electron microscopy image of the glass-ceramics samples revealed homogeneous distribution of spherical fluoride nanocrystals ranging 5-15 nm in size. The emission transitions from the higher excited sates (D-5(J), J = 1, 2, and 3) as well as lowered asymmetry ratio of the D-5(0)-> F-7(2) transition (forced electric dipole transition) to that of the D-5(0)-> F-7(1) transition (magnetic dipole) of Eu3+ in the glass-ceramics when compared to glass sample demonstrated the incorporation of dopant Eu3+ ions into the cubic BaGdF5 nanocrystals with higher local symmetry with enhanced ionic nature. The presence of absorption bands of Eu2+ ions and Gd3+ ions present in the glass matrix or fluoride nanocrystals in the excitation spectra of Eu3+ by monitoring emission at 614 nm indicated energy transfer from (Eu2+ -> Eu3+) and (Gd3+ -> Eu3+) in both glass and glass-ceramics samples. (C) 2014 Elsevier B.V. All rights reserved