Photoluminescence and structural similarity of crystals with oxide- fluoride stacking structure and oxyfluoride glass
K Shinozaki and S Sukenaga and K Ohara, JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 128, 1030-1037 (2020).
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 F-19- and B-11-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 K 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. (C) 2020 The Ceramic Society of Japan. All rights reserved.
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