Preperation And Luminescence Of Rare-earth Ions Doped Niobate And Phosphate Phosphors

Na0.5Sr0.25NbO3:xEu3+phosphors with cubic bulk morphology were prepared by molten salt method.The samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and fluorescence spectroscopy(PL).The morphology evolution process and luminescent properties were studied.CaZn2(PO4)2(CZP):Sm3+phosphors were synthesized by high temperature solid-state method.The radiation transition probability,non-radiation transition probability and internal quantum efficiency of CZP:Sm3+phosphors doped with different alkali metal ions were predicted by Judd-Ofelt theory.The effects of different alkali metal ions on the luminescence properties of CZP:Sm3+phosphors were analyzed from the perspective of electron transition.In order to obtain single phase and uniform morphology,the effects of reaction temperature,reaction time and molten salt content on the phase and morphology of Na05Sr0.25NbO3 were studied.The results show that the relative mass of molten salt and reactant has a great influence on the dispersion and uniformity of product particles.With the increase of temperature,the impurities in the product decrease gradually.In the time range of 1 to 6 h,the particle size of the product is inversely proportional to the reaction time,and the particle uniformity increases with the extension of time.The optimum reaction conditions for the synthesis of Na0.5Sr0.25NbO3 matrix were determined as s/o?9:1,reaction temperature is 1200? and reaction time is 6 h.The morphology evolution of Na0.5Sr0.25NbO3 particles is the Ostwald ripening mechanism of the growth of large particles and dissolution of small particles.On the basis of the optimum synthesis process,Na0.5Sr0.25NbO3:xEu3+phosphors with cubic particle morphology were prepared.In Na0.5Sr0.25NbO3:xEu3+ phosphors,the luminescent intensity of the phosphors increases gradually with the increase of Eu3+ions doping concentration.When the Eu1+ions doping concentration reaches 5 mol%,the luminescent intensity is the strongest.Further increase of Eu3+doping concentration will cause concentration quenching,leading to the decrease of luminescence intensity.The critical distance of energy transfer of Eu3+ions in Na0.5Sr0.25NbO3:xEu3+phosphors is Rc=20.92 A,and the way of energy transfer of Eu3+ ions is quadrupole-qUadrupole interaction.The transition probability and quantum efficiency under different excitation light were analyzed by J-O theory.The quantum efficiency and color purity under 466 nm excitation were higher than those under 396 nm excitation,but the color temperature was also relatively high.CZP:0.03Sm3+,CZP:Sm3+,0.03A+(A=Li,Na,K)phosphors were prepared by high temperature solid-state method.The cell parameters of CZP:0.03Sm3+,CZP:Sm3+,0.03A+(A=Li,Na,K)were obtained by Rietveld structure refinement.The order of volume size after incorporation was V(CZP:0.03Sm3+,0.03K+)>V(CZP:0.03Sm3+,0.03Na+)>V(CZP)>V(CZP:0.03Sm3+)>V(CZP:0.03Sm3+,0.03Li+).By comparing the optical band gap,it is found that the optical band gap decreases gradually with the increase of cell volume.However,because the substitution of Zn2+ions by Li+ions affected bottom of the conduction band of CZP,and in CZP:0.03Sm3+,Ca2+ vacancy defect weakens the binding ability of CZP to electrons.Therefore,the band gap of CZP:0.03Sm3+,0.03Li+is larger than that of CZP:0.03Sm3+.By comparing the emission spectra,it was found that the luminescence intensity of CZP:0.03Sm3+phosphors was significantly increased after Li+,Na+,K+ions were doped.In Li+doped ones,the luminescence intensity of CZP:0.03Sm3+phosphors was increased by nearly 3.7 times.According to J-O calculation,the non-radiative transition properbalities have been lessened and the radiative transition properbalities have been boosted by adding charge compensation ions compared to the CZP:0.03Sm3+phosphor,which leads to the improvement of the quantum efficiencies.By calculating the color purity of CZP:0.03Sm3+,CZP:Sm3+,0.03A+(A=Li,Na,K)phosphors,it is shown that CZP:0.03Sm3+,0.03Li+phosphors have the highest color purity,the best comprehensive luminescence performance and possess applicable value.