Time-resolved study of luminescence in soda-lime silicate glasses co-doped with Gd3+ and Eu3+

Energy transfer process in soda-lime glasses co-doped with Gd3+ and Eu3+, where a ground state of Gd3+, 8S7/2, was selectively excited to a 6IJ state by a 275-nm pulsed laser irradiation, was studied based on a time-resolved luminescence spectroscopy. The luminescence decay rate at 313 nm (Gd3+: 6P7/2 → 8S7/2) was observed to be (1.5 ± 0.2) × 102 s−1 (τ = 6.6 ± 0.6 ms) without Eu3+ and to increase monotonously with increasing co-doped Eu3+ concentration, giving an apparent quenching rate constant of (5.0 ±  0.5) × 10−18 ion−1 cm3 s−1 (≈(1.9 ± 0.2) × 103 mol%−1 s−1) for a 6P7/2 state of Gd3+ ion with Eu3+. The relaxation rate of a 6IJ state to a luminescent state 6P7/2 in Gd3+ ion was estimated to be (1.8 ± 0.2) × 106 s−1 from the rise rate at 313-nm luminescence (τrise ≈  0.56 μs), which was observed to be almost independent of the Eu3+ concentration. The luminescence intensity from Eu3+ at 591 nm and 613 nm monotonously increased with increasing Eu3+ concentration up to 0.33-mol% Eu3+, while it started decreasing at concentration of Eu3+ higher than 0.33-mol%, which was interpreted in terms of the resonant energy transfer to nearby Eu3+ resulting in the excitation to the Eu3+-O− charge transfer states.