Luminescent Properties and Energy Transfer Mechanism of Gd³⁺ and Eu²⁺ Co-doped Phosphate Glasses

Abstract

The phosphate glasses doped with Eu²⁺, Gd³⁺, respectively, and co-doped with Gd³⁺ and Eu²⁺ were prepared by high-temperature melting method. The transmission spectra, the excitation spectra, the emission spectra and the fluorescent decay time were investigated. The energy transfer process between Gd³⁺ and Eu²⁺ was studied. From the excitation spectra and the emission spectra of the phosphate glasses doped with Eu²⁺, we observed that the emission intensity of Eu²⁺ shows higher for 0.02 mol% Eu²⁺-doped phosphate glass. According to the excitation spectra and the emission spectra and the fluorescence decay curves, when the concentration of Eu²⁺ was 0.02 mol%, the optimal concentration of Gd³⁺ was 0.3 mol%. Based on Dexter theory, it is shown that the energy transfer between Gd³⁺ and Eu²⁺ was nonradiation energy transfer by analyzing the energy-level diagram. The fluorescence decay curves of Gd³⁺ were expressed by the Inokuti–Hirayama’s model and were used to analyze energy transfer mechanism between Gd³⁺ and Eu²⁺. And the energy transfer efficiency was also calculated.