Fluorescence characterization of heavily Eu3+-doped lanthanum gallate glass spheres with high quenching concentration.

Highly Eu2O3-doped (up to 30 mol%) La2O3-Ga2O3 glasses were synthesized by an aerodynamic levitation technique. The red emission associated with D05 level of Eu3+was most intense at 20 mol% Eu2O3, indicating a small effect of concentration quenching even at high Eu concentration. The fluorescence decay curves indicated that the dominant transition mechanism at high Eu concentration was fast energy migration among the Eu3+ ions, which averaged the environment of the Eu, yielding a nearly single-exponential decay of D05→F27 emission. Lifetime of the D05 level gradually decreased with Eu2O3 over the 5-25 mol% and rapidly decreased at 30 mol%, very consistent with the observed emission spectra.

Principal Vibration Modes of the La2O3-Ga2O3 Binary Glass Originated from Diverse Coordination Environments of Oxygen Atoms.

La2O3-Ga2O3 binary glass exhibits unusual optical properties owing to its high oxygen polarizability and low vibration energy. These optical properties include high refractive indices and a wide transmittance range. In this study, we performed classical molecular dynamics simulations on La2O3-Ga2O3 glass synthesized by an aerodynamic levitation technique. We have obtained structural models that reproduce experimental results, such as NMR, high-energy X-ray diffraction, and neutron diffraction. Based on our analysis, the structural features were clarified: 5-, 6-coordinated Ga, edge-sharing GaOx-GaOx polyhedral linkages, and oxygen triclusters. Additionally, the vibrational density of states was calculated by diagonalization of the dynamical matrix derived from the structural models and the results were compared with Raman scattering spectra. The mode analysis of the Raman spectra revealed that the principal bands at 650 cm-1 were mainly attributed to the stretching modes of the bridging and nonbridging oxygens. Meanwhile, the shoulder bands at the highest frequency of 750 cm-1 were mainly attributed to the stretching modes of the bridging oxygens and oxygen triclusters. The structural models obtained in this study well describe the characteristic local structures and vibrational properties of the La2O3-Ga2O3 glass.