Luminescent properties of Eu³⁺ doped germanosilicate red glass

Eu3+ doped germanosilicate red glass was prepared by traditional high temperature melting method. The structure and optical properties of the samples were characterized by X-ray diffraction, photoluminescence spectra, Fourier transform infrared spectroscopy, absorption spectra, fluorescence decay time and CIE chromaticity coordinates. The density of the samples was measured. The band gap of the samples and the spacing of the doped rare earth ions were calculated theoretically. It is shown that the red emissions of Eu3+ at 589 nm and 614 nm are the main emissions in visible wavelengths, and the optimal concentration is 2.0 mol%, when the Eu3+ spacing is 10.337 angstrom. With the increase of Eu3+ concentration, the general trend of indirect and direct band gaps decreased from 3.977 eV to 2.952 eV and 3.501 eV to 2.577 eV, respectively. The [GeO4] tetrahedron, [GeO6] octahedron and [GeO4]&[SiO4] co-exist in the glass network structure, and the change of Eu2O3 concentration has a certain influence on the glass structure. All the samples emit light in the red region. The color temperature of the prepared glass is between 1859 and 2123 K under the excitation of ultraviolet light at 394 nm, and the color purity is all above 80%.