Investigation On Synthesis And Optical Properties Of Luminescent Materials CaWO₄System

In our paper, series of red-emitting phosphors containing Sr_xCa_0.88-xWO₄:0.12Eu³⁺,Ca_0.82-xWO₄:0.12Eu³⁺, x In³⁺and Ca_0.82-xWO₄:0.12Eu³⁺, x Gd³⁺（0≤x≤1）, have beenprepared by a traditional high-temperature solid method. Meanwhile, themorphologies, structures and optical properties of products synthesized werecharacterized by X-ray diffractometer （XRD）, scan electron microscopy （SEM）, X-rayphotoelectron spectroscopy （XPS） and photoluminescence （PL） analysis, respectively.We also studied the influence of luminescence properties by doping alkali metal ionsand halogen ions in the phosphor system Sr_xCa_0.88-xWO₄:0.12Eu³⁺（0≤x≤1）. Besides,the effect of the doping concentration, soaking time and calcination temperature onthe luminous intensity of the products was also investigated. Furthermore, theluminescent mechanism of optical materials prepared was preliminary elucidated.Sr_xCa_0.88-xWO₄:0.12Eu³⁺（0≤x≤1） red phosphors were synthesized successfully byhigh-temperature solid method. Studies showed that an optimum Sr2+doped molarconcentration of0.15at1100℃was attained, when the concentration of Eu³⁺is0.12.The luminous intensity of the materials prepared was enhanced significantly by theincorporation of alkali metals. We also investigated the influence of alkali metal ionsand halogen ions on the phosphors. Owning to the charge balancing of the alkalimetal ions K+and halogen ions Cl-, the luminous intensity of the phosphors preparedwas much stronger than the phosphors only doped with K+.Ca_0.82-xWO₄:0.12Eu³⁺, x In³⁺（0≤x≤1） red phosphors were successfully preparedby solid state method. It was found that Eu³⁺could be very efficient sensitized withco-doped In³⁺. The best molar concentration of In³⁺at1100℃was0.06, when the concentration of Eu³⁺is0.12. The luminescence mechanism for In³⁺in CaWO₄:Eu³⁺was elucidated. The sizes of particles prepared are1-2μm and the effects of differentcalcining temperatures and soaking time on the emission intensities of the phosphorCaWO₄:Eu³⁺, In³⁺were also investigated. Consequently, the optimal calcinedtemperature is1100℃and the best soaking time is3hours.We synthesized the Ca_0.82-xWO₄:0.12Eu³⁺, x Gd³⁺（0≤x≤1） materials throughsolid state method. It can be observed that the luminescence intensity is dramaticallyincreased by the incorporation of Gd³⁺ions into the phosphor, and the emissionintensity is almost2.2times of that of Ca0.88WO4:0.12Eu³⁺when the molarconcentration of Gd³⁺of the phosphor excited at396nm was0.04. Meanwhile, theenergy transfer Eu³⁺and Gd³⁺ions between was found, and the luminescentmechanism was preliminary elucidated. The sizes of particles prepared are about2μmand the effects of different calcining temperatures on the emission intensities of thephosphor CaWO₄:Eu³⁺, Gd³⁺were also studied. Furthermore, the evident enhancedemissions were studied in CaWO₄:Eu³⁺, Gd³⁺with boric acid, when the mole ratio ofH3BO4was0.03, the luminescence capability was optimum.