| In recent years, white light emitting diodes (LEDs) are considered to be the hotarea of research in the field of solid-state lighting due to their higher luminousefficiency, longer lifetime and environment friendly compared with the conventionallight sources such as incandescent lamps or fluorescent lamps. Until now, the mostwidely used commercial white LEDs are fabricated by combining high performanceblue or near UV InGaN chip with phosphors. Compared to the blue chip based whiteLEDs, the white LEDs obtained by combining near UV LED chips with tricolorphosphors have the advantages, for instance, high color rendering index and colorstability. Therefore, the primal problem to obtain high quality LEDs is looking forsome high-efficient phosphors that can be excited by near-UV light.Phosphate phosphors have attracted more attention as host materials for theapplication in near UV LEDs due to their low synthesis conditions, low cost, highluminous efficiency and high chemical stability. The main purpose of this study is toobtained high-efficient phosphors that can be used in near-UV LEDs. Thus, studies onthe crystal structure and photoluminescence properties of Eu2+/Ce3+, Mn2+codopedSr9Sc(PO4)7and Sr9Sc(PO4)7: Eu3+have been carried out.Electron trapping materials is also called the photostimulated luminescencematerials. This kind of material has been always focused on extensively Since1986,the photostimulated luminescence materials were first referred by Lindmayer, it hasbeen attracted increasing interest. This materials can be used on optical storage, X-rayimaging, infrared detection and photostimulated luminescence materials. At present,the commercial photostimulated luminescence materials which is used in thephotostimulated luminescence materials aspect is alkaline sulfides. However, thechemical stability of alkaline sulfides is poor and the product of decomposition willpollute the environment. Therefore, it is urgent to search new photostimulated luminescence materials which have good chemical stability. In this paper, we improvethe photostimulated luminescence properties of Sr3Al2O5Cl2: Eu2+through codopedrare earth ions.The main studies and results are listed as follow:1、Eu2+–Mn2+codoped yellow-emitting Sr9Sc(PO4)7phosphors have beensynthesized by solid-state reactions. The synthesis, structure refinement, andluminescence properties of the obtained phosphor were investigated in detail. Theobtained phosphor exhibits a strong excitation band between250nm and450nm,matching well with the dominant emission band of a near-UV light-emitting-diode(LED) chip. Upon excitation at365nm, the Sr9Sc(PO4)7: Eu2+, Mn2+phosphor showsstrong yellow emissions centered at510nm and610nm. With increasing theconcentration of Mn2+, the FWHM can reach170nm.The energy transfer mechanismfrom Eu2+to Mn2+in Sr9Sc(PO4)7: Eu2+, Mn2+has been studied based on the decaylifetime data.2、A series of Ce3+and Mn2+co-doped Sr9Sc(PO4)7phosphors have beensynthesized by high temperature solid state reaction and their luminescence propertiesare investigated. The obtained phosphors exhibit a broad excitation band ranging from240nm to350nm and two emission bands centered at about370nm and610nm upon310nm excitation, resulting from the5d–4f transitions of Ce3+and the d–d forbiddentransition of Mn2+, respectively. Energy transfer mechanism from Ce3+to Mn2+inSr9Sc(PO4)7host matrix was studied based on the decay lifetime data. Througheffective energy transfer, a color-tunable emission varied from blue to reddish orangecan be realized by adjusting the ratio of Ce3+to Mn2+.3、A series of Eu3+ions doped Sr9Sc(PO4)7orange–red emitting phosphors havebeen prepared by solid-state reaction method. Photoluminescence properties undernear-ultraviolet (NUV) light excitation of the samples have been carried out. Thestudies show that the samples can be effectively excited by NUV (394nm) whichmatches to the output wavelengths of near UV chips and exhibits intense orange–redemissions. Eu3+concentration was found to be optimum at x=0.4and the thermalquenching temperature of Sr9Sc(PO4)7:0.4Eu3+is above200℃.4、Sr3Al2O5Cl2: Eu2+, Ln3+(Ln=Nd、Sm、Dy、Tm、Yb) phosphors have beensynthesized by solid-state reactions. The effect of different rare earth ions onphotostimulated luminescence properties has been studied. And strong andlong-lasting photostimulated luminescence is observed and studied in Eu2+and Tm3+ codoped Sr3Al2O5Cl2under980nm continuous stimulation after UV and blue lightpre-irradiation. Compared to the Eu2+singly doped one, the PSL intensity and energystorage capacity in the doubly doped material are enhanced by a factor of441and91,respectively. The study indicates that codoping Tm3+leads to a large increase of trapsthat enlarge energy storage capacity as three times as the commercial phosphor SrS:Eu2+, Sm3+. |
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