We measured the thermal-glow curves of ZnS:Ag,Al phosphors because ZnS phosphors are one of the most important types of phosphors for electron-irradiated types of displays such as Braun tubes, projection tubes, field emission displays, and transmission electron microscope. To investigate traps in the thermal-glow curves of ZnS:Ag,Al, we measured the thermal-glow curves of ZnS:Al and ZnS:Ag phosphors. The trap peaks were observed at 144 K and 230 K for ZnS:Al and ZnS:Ag, respectively. The trap peak at 144 K for ZnS:Al is associated with a bimolecular-type-Al trap. Whereas the trap peak at 230 K for ZnS:Ag is associated with a monomolecular-type-Ag trap because the shape of the thermal-glow curve tails off toward the low-temperature side. We synthesized ZnS:Ag,Al phosphors in a flow of H2S gas at 900-1200 °C and observed an electron trap at 430 K in the thermal-glow curve for these phosphors. We also found that the thermoluminescence (TL) intensity of the electron trap at 430 K decreased with increasing in the gas flow rate of H2S. Hence, we assigned it to a deep sulfur vacancy. Moreover we analyzed the luminescent properties of phosphors with various sulfur-vacancy concentrations.
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