Synthesis And Characterization Of Red-Emitting Phosphors Eu³⁺ Doped Molybdate And Mn⁴⁺ Doped Fluotitanate

Recently,the red phosphors of Eu3+ doped molybdate have become a hot topic of the researchers due to their double excited wavelengths and high R value(The higher of the R value,the more pure of the red light).In addition,they also have the advantages of good chemical stability and thermal stability,environment friendly and compounded easily.While the phosphors of Mn4+doped fluorine with high quantum yields.Their unique d-d transition of Mn4+makes them have narrowband emission in the red light area,and wide absorption band in the blue area.So they can be employed in the lighting,holography,laser technology and metrology widely.Based on a large number of literatures research,a series of LiLa(MoO4)2:xEu3+ phosphors were prepared by high temperature solid phase method.On this basis,two series of LiLa(MoO4)2:xEu3+@(NaCl)ywt and LiLa(MoO4)2:xEu3+@(NaF)ywt phosphors were prepared with the coating method.Then,two series of K2TiF6 ·BaF(HF2):xMn4+ and K2TiF6:xMn4+,M2+(M=Mg,Ca,Sr,Ba,Zn)phosphors were prepared with cations exchange method.The structures of the phosphors and the photoluminescence(PL)properties,morphology were investigated by powder X-ray diffraction(XRD)measurement,excitation and emission(PLE&PL)spectra and scanning electron microscopy(SEM).The luminescence decay curves and the photoluminescence quantum yields were available from an Edinburgh FLS980 fluorescence spectrophotometer.The research results and highlights of this paper are as follows:1.After coating with NaCl and NaF,the luminescence intensity of LiLa(MoO4)2:xEu3+ phosphors was greatly enhanced,but the effect of its luminous intensity was far greater than that of their R value.Besides,the R value of samples LiLa(MoO4)2:xEu3+@(NaCl)ywt are all greater than 8,while for the samples LiLa(MoO4)2:xEu3+@(NaF)ywt,all R values were greater than 5.The results indicated that the samples were primarily due to the electric dipole transition(5D0?7F2).2.The best coating content of NaCl was 48%.It was much larger than that of NaF(2.5%).The effect of NaF on luminous intensity of LiLa(MoO4)2:Eu3+was more significant than that of NaCl.The effect of the two coating materials on the R value was different.After coating with NaF,the R value of the sample showed a downward parabola with change of the coating content,and after coating with NaCl,the R value of the sample showed the upward parabola.Therefore,the effects on fluorescence properties of the samples was different when the anions of the coating materials were different.3.KF had an induced fluorescence effect on the sample of K2TiF6·BaF(HF2):Mn4+.Without KF in the reactions,the samples will almost have no fluorescence.When the addition of KF was 6 g,the fluorescence intensity of the sample was strongest.Fluorescence life and quantum yield of the optimal sample were 4.76 ms and 60.75%respectively.4.The alkali metal ions of M2+(M=Mg,Ca,Sr,Ba,Zn)had certainly influenced effect on fluorescence property of the samples of K2TiF6:Mn4+,M2+.The results showed that the fluorescence intensity of K2TiF6:0.0253Mn4+ was strongest,and its decay lifetime and the photoluminescence quantum yields were 5.3 ms and 94.04%.And the sample of K2TiF6:0.0253Mn4+ contains perfect hexagonal phase micro-sticks with sizes about 0.5 × 0.5 × 3.0 ?m,respectively.5.The fluorescence properties of K2TiF6:Mn4+,M2+ were related to the solubility of fluoride in HF solution.The higher of the solubility,the fluorescence intensity of the samples will be higher.When M2+ was added to the solution,the MF2 will be generated,which will be coated on K2TiF6:Mn4+surface,thereby the fluorescence effect of K2TiF6:Mn4+ will be weakened.6.Mn4+ is in the center of[MnF6]2-,and there is no interaction between Mn4+ and water molecules,so the photoluminescence of Mn4+ in the water will not be quench.Therefore,K2TiF6 Ba(HF2):Mn4+ and K2TiF6:Mn4+,M2+phosphor in the water will be stable.