Development of novel oxyfluoride glasses and glass ceramics for photolu-minescence material by a containerless processing

In this study, novel Eu2O3-BaF2-La2O3-B2O3 oxyfluoride glasses and glass ceramics were developed by a containerless processing. Differential thermal analysis (DTA) analysis was performed to analyze the thermophysical properties of oxyfluoride glasses doped with Eu2O3, and photoluminescence (PL) characteristics were analyzed to evaluate the luminous efficiency depending on the degree of crystallinity. The glass transition temperature decreased with increasing BaF2 concentration since BaF2 acts as a network modifier in this glass system. In addition, thermal stability which can be estimated by the difference between the glass transition temperature and the onset temperature of the crystallization decreased with increasing BaF2 contents. The peak related to the BaF2 crystal was confirmed after the crystallization by X-ray Diffraction (XRD) analysis. Photoluminescence intensity increased after the crystallization which indicates that the Eu3+ ions are sited in BaF2 crystal. La 3d(5/2) x-ray photoelectron spectroscopy (XPS) and F1s XPS spectra were analyzed to precisely understand the behavior of the fluorine ion in the glass structure. Fluorine tends to bond with the network modifying cations such as La3+ and Ba2+ ions and after the crystallization the La-F bonds decreased because F- ions used to form BaF2 crystals.