Luminescence And Regulation Of Sr₆Ca₄?PO₄?₆F₂ Phosphor Doped With Rare Earth Ions And Transition Metal Ions

In this thesis,a series of Sr₆Ca₄?PO₄?₆F₂ phosphors were synthesized by a high-temperature solid-state reaction method,which includes Sr₆Ca₄?PO₄?₆F₂:xCe³⁺,Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,yTb³⁺,Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,zSm³⁺,Sr₆Ca₄?PO₄?F₂:0.14Ce³⁺,wTb³⁺,0.13Sm³⁺,Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,yMn²⁺and Sr₆Ca₄?PO₄?₆F₂:0.02Eu²⁺,yMn²⁺.In the way of energy transfer from sensitizer(Ce³⁺/Eu²⁺)to activator(Tb³⁺/Sm³⁺/Mn²⁺).The color of phosphor can be adjusted and white light emission can be formed.XRD pattern,fluorescence spectrum,fluorescence decay curve,chromaticity coordinate and color rendering index of the as-prepared samples are measured and used to characterize the properties.In order to improve the luminescence performance of phosphors,changing cations in host and doping fertilizer are used.The effects of different control measures on the luminescence performance of phosphors were studied.The results are shown below:?1?The series Sr₆Ca₄?PO₄?₆F₂:xCe³⁺phosphors were synthesized by high-temperaturesolid-state reaction method.Since the emitted photon of Ce³⁺came from its internal 5d-4f energy level transition,the 5d energy level was in direct contact with the external fieldenvironment and was easily affected by the crystal field.So its energy level distributionwas wide.Generally,due to the different crystal field environment in the matrix,theemission of Ce³⁺can be extended from the UV region to the yellow light range.InSr₆Ca₄?PO₄?₆F₂,there are different cation lattice sites,which provide differentcoordination environments for Ce³⁺ions,resulting in different crystal field environmentsof Ce³⁺.In the series of phosphors synthesized,with the increase of Ce³⁺concentration,the emission peak showed a significant red shift.For different doping amounts,the crystalfield environment of Ce³⁺ions will change,which is explained from multiple aspects.Moreover,the quenching concentration of Ce³⁺ion in Sr₆Ca₄?PO₄?₆F₂ was determined,providing the optimal doping concentration as sensitizer.?2?TheseriesSr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,yTb³⁺,Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,zSm³⁺,Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,wTb³⁺,0.13Sm³⁺phosphors were synthesized byhigh-temperature solid-state reaction method.We selected the best doping concentrationof Ce³⁺and co-doped Ce³⁺/Tb³⁺and Ce³⁺/Sm³⁺in Sr₆Ca₄?PO₄?₆F₂.The energy transferbetween Ce³⁺and Tb³⁺,Sm³⁺ions is used to realize the adjustable color of phosphor.Moreover,the interaction mechanisms of Ce³⁺and Tb³⁺,Ce³⁺and Sm³⁺were determinedto be dipole-dipole interaction.The combination of Ce³⁺,Tb³⁺,Sm³⁺is then used togenerate white light emission.However,due to that in the Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,wTb³⁺,0.13Sm³⁺series phosphors,the blue component is higher,the red component isless.In addition,the narrow peak emission of Tb³⁺and Sm³⁺resulted in a low colorrendering index of 56.4.Therefore,there is still a certain gap to practical applications.?3?The series Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,yMn²⁺and Sr₆Ca₄?PO₄?₆F₂:0.14Ce³⁺,yMn²⁺,zMg²⁺?z=0,0.4,1.0,1.6?phosphors were synthesized by high-temperature solid-statereaction method.The phase of the synthesized material was determined to be single byXRD of the sample.The mismatch between Mn²⁺strength enhancement and Ce³⁺strength degradation in the co-doping system of Ce³⁺,Mn²⁺was analyzed.It wasproposed that the concentration quenching phenomenon caused by the high dopingconcentration of the activator(Mn²⁺)in the sample,the distance between Mn²⁺ions wasincreased by introducing Mg²⁺ions and regulating the occupation of the activator(Mn²⁺),so as to weaken the concentration quenching effect between Mn²⁺and reduce the losscaused by non-radiation transition.When the concentration of Mg²⁺was 1.0,theluminescence performance of the sample was improved most obviously.In thesynthesized samples SCPF:0.14Ce³⁺,yMn²⁺,1.0Mg²⁺,when the concentration of Mn²⁺is 0.4,the powder realize white light emission,and the powder shows relatively goodoptical properties.The color coordinate is?x=0.3389,y=0.3422?,which is in the whitelight region.Its color rendering index is 67.8,color temperature is 4529K.The colorrendering index and color temperature were improved compared with the combination ofCe³⁺/Tb³⁺/Sm³⁺.?4?The series Sr₆Ca₄?PO₄?₆F₂:0.02Eu²⁺,yMn²⁺,Sr₆Ca₄?PO₄?₆F₂:0.02Eu²⁺,0.3Mn²⁺,zH₃BO₃and Sr₆Ca₄?PO₄?₆F₂:0.02Eu²⁺,0.3Mn²⁺,wMg²⁺phosphors were synthesized byhigh-temperature solid-state reaction method.The phase of the synthesized material wasdetermined to be single by XRD of the sample.The decrease of quantum efficiency ofEu²⁺,Mn²⁺doped in the matrix was explained.It is proposed that there are"bottleneckeffect"and"anti-bottleneck effect"in the energy transfer process from Eu²⁺to Mn²⁺andconcentration quenching effect of activator.The luminescence performance wasimproved by using H₃BO₃ as auxiliary agent and regulating cations in Sr₆Ca₄?PO₄?F₂.Two different regulation methods both improved the quantum efficiency of samples.Inorder to study the difference in emission intensity of Eu²⁺and Mn²⁺between two kinds of regulatory processes,the changes in the crystal field environment of the luminescent center were analyzed by means of refinement,and the corresponding explanations were given.