White-light emission and red scintillation from Mn2+ ions single-doped aluminum-silicate glasses

A series of Mn²⁺ single-doped 0.2Gd₂O₃-0.2Al₂O₃-0.6SiO₂ (GAS: xMn²⁺) glasses with Si₃N₄ as reducing agent were prepared. The presence of [SiO_4-x] defects and Mn²⁺ ions was determined from the absorption and excitation spectra of the glasses. With the increase of Mn²⁺ concentration, the intensity of blue emission decreases, while the intensity of red emission increases. The color coordinate of GAS: 6Mn²⁺ glass is (0.264, 0.226). The lifetime of the glasses was tested. Under the monitoring of 440 nm, the fast components (τ_f) are between 17 and 85 μs, and the slow components (τ_s) are between 200–650 μs. The former belongs to [SiO_4-x] defects, and the latter is [⁴E(G), ⁴A₁(G)]→⁶A₁(S) transition of Mn²⁺ ions. Under the monitoring at 630 nm, the τ_f are between 110 and 300 μs, and the τ_s are between 680 and 1220 μs, which are due to ⁴T₁(G)→⁶A₁(S) transition of Mn²⁺ ions and Mn²⁺ pairs, respectively. The energy transfer mechanism of [SiO_4-x] defect→Mn²⁺ ions are explained. The efficient [SiO_4-x] defect →Mn²⁺ ions energy transfer process was demonstrated by time-resolved photoluminescence, and the energy transfer efficiency is over 85%. The maximum photoluminescence quantum yield (PL QY) of the glasses can reach 15.87%. The thermal activation energy of the glasses was calculated. In addition, X-ray excited red luminescence spectra and the mechanism of the glasses were investigated.