The nondoped Mg2SnO4 material with inverse spinel structure was synthesized by solid state reaction. This phosphor showed a broad green emission band covering 470–550 nm under 291 nm excitation, which was due to the recombination of F centers with holes. Stimulated by 980 nm infrared laser, the green photostimulated luminescence was first observed in a nondoped oxide. After ultraviolet irradiation, the green persistent luminescence of Mg2SnO4 could be seen in darkness for about 5 h. The decay curves revealed that the long persistent luminescence was governed by tunneling mechanism and it proved the presence of different trap clusters in Mg2SnO4. These trap clusters (such as [SnMg••–Oi″], [SnMg••–2e′], and [SnMg••–e″]) induced the trap levels with different depths in band gap and corresponded to the three components (at 110, 168, and 213 °C) of the thermoluminescence glow curve of Mg2SnO4. These trap levels with different depths were proved to be not independent. It revealed that the shallow traps (110 °C) and part of the deep traps (168 and 213 °C) were involved in the persistent luminescence. Meanwhile, all the shallow and deep traps were responsible for the photostimulated luminescence. Accordingly, the photoluminescence, persistent, and photostimulated luminescence mechanisms of the nondoped Mg2SnO4 material were first proposed.

A novel orange-yellow emitting Sr3Al2O5Cl2:Eu(2+), Tm(3+) phosphor with bright and long persistent luminescence (LPL) has been newly developed. The incorporation of Tm(3+) into the Sr3Al2O5Cl2:Eu(2+) as an auxiliary activator dominates its long persistent luminescence and thermoluminescence characteristics to a large extent. The emissions in Sr3Al2O5Cl2:Eu(2+), Tm(3+) for both fluorescence and LPL are due to the 5d → 4f transitions of Eu(2+). The orange-yellow long persistent luminescence with the chromaticity coordination of (0.53, 0.46) can persist for nearly 220 min at recognizable intensity level (≥ 0.32 mcd/m2). This investigation provides a new and efficient long persistent phosphor which enriches the color of the existing LPL.

No abstract

A real high power vacuum ultraviolet light source is applied to the investigation on the vacuum ultraviolet irradiation degradation of BaMgAl10O17:Eu2+ phosphor. The degradations of emission intensity and color quality of the sample are clearly observed after irradiation. It reveals that the oxidation of Eu2+ during irradiation is partly responsible for the degradations. The excitation and absorption spectra show that some traps generated during irradiation have negative influence on the luminescence of sample and these traps have been identified as positively charged oxygen vacancies by positron annihilation. The investigations on host emission and decay curve further confirm that these oxygen vacancies are involved in the perturbation of energy transfer from the host to Eu2+ and finally result in the degradation.

No abstract