Synthesis And Luminescent Properites Of Rare Earth Doped Double Tungsten-molybdate Luminescence Materials

In this paper, a series of rare earth ions doped tungstates, molybdates andvanadates have been synthesized. Their crystal structure andphotoluminescence （PL） were investigated and discussed.The synthesizing conditions have been optimized in our work, including thesintering temperature and the concentration of activators. Powder X-ray diffraction（XRD） was used for crystal phase identification., and the chemical state of theelements in the phosphors was interpreted using XPS spectra. The effect ofactivators doping concentration, co-doping ion concentration, annealing temperatureon the photoluminescence （PL） of the phosphors were investigated in detail.Photoluminescence excitation and emission spectra were used to characterize theresulted phosphors, in order to optimized their luminescence performance.NaLa_0.9Eu_0.1（MoO₄）（WO₄） was synthesized by the modified solid-statereaction. It is found that the maximum emission intensity corresponds to theconditions that the concentration of （WO₄）^2-is50%, the concentration of Eu³⁺is10%and the calciningtemperature is at900℃. The photoluminescence studies showthat a dominant red emission line at around616nm is observedunder467nm excitation.NaY_0.87Eu_0.13（WO₄）_1.2（MoO₄）_0.8was synthesized by the modified solid-statereaction. The maximum emission intensity corresponds to the conditions that theconcentration of （MoO₄）^2-is40%, the concentration of Eu³⁺is13%and the calciningis at900℃. The photoluminescence studies show that a dominant redemission line at around616nm is observed under467nm excitation.NaY_0.84La_0.03Eu_0.13（WO₄）and KY_0.86La_0.06Eu_0.08（WO₄）₂were synthesized bythe modified solid-state reaction. The maximum emission intensity corresponds tothe conditions that the concentration of Eu³⁺are13%and18%,the concentration ofLa³⁺are3%and6%respectively, and the calcining temperature is at900℃. Thesephosphors show the strongest emission at616nm under396nm excitation.LaBa₂VO₆: Eu³⁺phosphors were prepared by the modified solid-statereaction．The results showed that the sample clcined at about900℃with theEu³⁺concentration is11%has the highest emission intensity. The phosphors showthe strongest sharp peaks at about616nm upon excitation at466nm.The above phosphors obtained show strong red emission centered at616nmupon excitation at396and467nm, which matches well with the commercially available LED chips.(Sr_0.5Ba_0.5)MoO₄:Pr³⁺,K⁺phosphors were prepared by the solid-state reaction.Using the Pr³⁺as activators, K⁺as charge compensation agent, and polyethyleneglycol （PEG） as dispersant. The effect of annealing temperature on the crystalstructure and the effect of the charge compensation agent （K⁺） doping concentration,activator (Pr³⁺) doping concentration, annealing temperature,the replacement way onthe photoluminescence of the phosphors were investigated in detail. Theinvestigation of their luminescence properties indicates that the strongest emission at646nm under450nm excitation when the concentration both Pr³⁺and K⁺concentration were1%and the calcining temperature was at1000℃. The excitationspectra of the phosphors are nicely in agreement with blue LED chips, too.