RESUMO
A warm persistent luminescence (PersL) material SrBaZn2Ga2O7:Bi3+ was prepared using the conventional high-temperature solid-phase reaction method. We first investigated the PersL properties of SrBaZn2Ga2O7:Bi3+ in detail via PersL spectra, PersL excitation spectrum, PersL decay curves, and thermoluminescence (TL) spectra. The highlight of this study is that in addition to the 254 nm light source, the low-energy light source of 365 nm and sunlight can effectively excite electrons and charge traps, resulting in preferable orange PersL performance. The PersL decay time of the representative sample can last for 960 s after excitation by a 365 nm light source and 900 s after excitation by simulated sunlight. Meanwhile, the PersL color can be regulated by changing the excitation wavelength. In order to explain the infrequent PersL phenomena after different light source excitations, we recorded a series of TL spectra as a function of different light sources, different charging times, and different decay times to reveal the distribution of traps in the material and the influence of trap distribution on trapping and detrapping processes. This novel sunlight-activated orange PersL material is expected to promote the development of sunlight-activated PersL materials and expand potential applications in solar energy utilization and anticounterfeit marking.
RESUMO
Thermoluminescence (TL) properties of Ce(3+) and Yb(3+) co-doped in Y(3)Al(5)O(12) (YAG) were studied with the aim of determining the location of energy levels of Ce(3+) and Yb(2+) relative to the bottom of the conduction band (CB) and the top of the valence band (VB) of YAG. The TL glow peak at about 180 °C when heating rate ß = 1°C s(-1) was assigned to electron release from Yb(2+), indicating that Yb(3+) acts as an electron trap. The trap depth, which is the depth of the ground-state level of Yb(2+) below the bottom of the CB, was derived from the temperatures of the maximum of the TL glow peak at different heating rates. The value is, within the experimental and theoretical uncertainties, in good agreement with that derived from the O(2-) --> Yb(3+) charge transfer energy. Thermoluminescence excitation spectroscopy (TLES) was used to establish the location of energy levels of Ce(3+). From the derived data the energy level diagram of YAG:Ce(3+), Yb(3+) is constructed and possible electron transfer processes are discussed.
