Syuji Matsumoto

High Photoluminescent Property of Low-Melting Sn-Doped Phosphate Glass

The authors report on the quantum efficiency (QE) of UV-excited photoluminescence measured in SnO–ZnO–P2O5 glass developed as rare earth (RE)-free material for light emitting diode (LED) applications; we report what is, to the best of our knowledge, the highest value of QE ever reported. It is notable that the QE value of the present RE-free glass (~90%) is comparable to that of RE-doped glass. For future LED applications, we have emphasized that the low-melting glass will be one of the most industrially favorable inorganic materials to replace organic sealants that suffer degradation by strong LED irradiation.

White light emission of Mn-doped SnO-ZnO-P_2O_5 glass containing no rare earth cation

The authors have demonstrated white light emission of rare earth (RE)-free Mn-doped SnO-ZnO-P(2)O(5) glass. The RE-free glass shows white light emission with a high value of quantum efficiency (QE) comparable to conventional crystalline phosphor. It is notable that the high QE value is attained for RE-free transparent glass, and the broad emission can be continuously tuned by both the amount of activator and the composition of the glass. Since this glass possesses low-melting property, we emphasize that the glass phosphor will lead to the development of a novel inorganic white-light-emitting device in combination with a solid state UV light-emitting source.

Correlation between emission property and concentration of Sn^2+ center in the SnO-ZnO-P_2O_5 glass

The authors report on the correlation between the photoluminescence (PL) property and the SnO amount in SnO-ZnO-P2O5 (SZP) glass. In the PL excitation (PLE) spectra of the SZP glass containing Sn2+ emission center, two S1 states, one of which is strongly affected by SnO amount, are assumed to exist. The PLE band closely correlates with the optical band edge originating from Sn2+ species, and they both largely red-shifts with increasing amount of SnO. The emission decay time of the SZP glass decreased with increasing amount of SnO and the internal quantum efficiencies of the SZP glasses containing 1~5 mol% of SnO are comparable to that of MgWO4. It is expected that the composition-dependent S1 state (the lower energy excitation band) governs the quantum efficiency of the SZP glasses.

Correlation between preparation conditions and the photoluminescence properties of Sn2+ centers in ZnO–P2O5 glasses

Photoluminescence (PL) and coordination states of Sn2+ centers in 1SnO–68ZnO–31P2O5 (SZP31) glass prepared under different conditions are examined. When prepared in air, the local coordination state of Sn2+ centers depends on the starting material. In contrast, the PL properties of Sn2+ centers of the glass prepared under inert atmosphere conditions are independent of the starting material because of elimination of the oxidation reaction. 119mSn Mossbauer and X-ray absorption fine structure analyses indicate that most of the Sn2+ centers in the SZP31 glass prepared in an inert atmosphere exist at a SnO-like coordination state, possessing a coordination number greater than 2. It is assumed that the more highly coordinated Sn2+ is the origin of high PL intensity with high quantum efficiency.

High efficient white light emission of rare earth-free MnO–SnO–ZnO–P2O5 glass

White light emission of rare earth (RE)-free Mn-doped SnO–ZnO–P2O5 glass is demonstrated. Glass transition temperature of the obtained glass is below 440°C, which assures the application to sealant of solid state light emitting devices. The RE-free transparent glass shows white light emission with a high value of quantum efficiency (QE) comparable to conventional crystalline phosphor by excitation of deep UV light. The broad emission of RE-free transparent glass can be continuously tuned by both the amount of activator and the composition of the glass without decrease of the QE value.

Correlation between valence state of tin and elastic modulus of Sn-doped Li2O-B2O3-SiO2 glasses

The correlation between the longitudinal elastic modulus c11 and tin valence state in Li2O–B2O3–SiO2 ternary glasses is investigated. Substitution of B2O3 for SiO2 increases the glass-transition temperature and c11 but decreases the melting temperature. 119Sn Mossbauer spectra show that the valence state of tin increased with increasing molten temperature, Tmolten, in air, and that it also affects the c11 value even though the 1.0 mol. % addition. The c11 values, whose error bars are governed by those of density, suggest that the addition of SnO2 increases c11 whereas SnO decreases. The relationship between Tmolten and the amount of Sn2+ suggests that the main factor affecting the tin valence state is oxygen, whose reactivity may correlate with the glass melt viscosity.