Photoluminescence and structural similarity of crystals with oxide–fluoride stacking structure and oxyfluoride glass

抄録

In this study, we developed a highly efficient photoluminescent glass from the design of a short–medium range structure and the photoluminescence (PL) of a fluoroborate glass. We investigated PL and the structures of BaMgBO₃F ceramics and the B₂O₃-added composition of glasses and glass-ceramics. The glass showed higher quantum yield (QY) than ceramic samples, i.e., the QY was 95 % for glass and 51 % for ceramics, by a 395 nm excitation. The glass can contain a large amount of emission centers with small concentration quenching, and 15 % Eu-doped glass exhibited higher PL intensity and QY than commercial Y₂O₃:Eu³⁺ phosphor. The origin of a high QY and small concentration quenching were investigated by the structural analysis. The glass structure was investigated using ¹⁹F- and ¹¹B-magic-angle spinning nuclear magnetic resonance, extended X-ray absorption fine structure of Ba K-edge, and high-energy X-ray diffraction. Moreover, the glass structure was simulated by molecular dynamics. It was found that the glass had a structural similarity with BaMgBO₃F crystal in the short-range order of B and Ba. The glass had a clear selectivity that B preferred to bind to O and Ba preferred to bind to F. The glass also exhibited unique medium-range ordering. Two types of Ba–Ba displacements were observed, which could be attributed to in-plane and out-plane layered displacements of the corresponding crystal, with the stacking structure of oxide–fluoride layers indicated by the radial distribution. The glass showed anion segregation, also similar to the layer-stacking structure of BaMgBO₃F. This made the low phonon sites coordinated with F compatible with the asymmetric sites derived from the oxide network segregation, resulting in high PL efficiency. The study results can contribute to the use of rare-earth ion-doped glasses in various applications such as laser and optical amplification, white light emitting diode (LED) lighting, and sensing technologies.