Spectral Regulation Of Eu²⁺ Or Ce³⁺ Doped Phosphate Phosphors Via Energy Transfer

White light-emitting diodes as a new type of solid-state light-emitting material,have wide aplication in the lighting and display,such as television tubes,smartphone screens,due to their good optical stability and high conversion efficiency.In recent years,there are two main methods to realize white light emission in a single-phase host.One is doping a rare earth luminescent ion in the matrix,and the other is energy transfer through co-doping.Based on the energy transfer mechanism,three host of KBaPO₄?Ba₃CeK?PO₄?₃F?K₂CaPO₄F were prepared in this paper.Different luminescent ions were doped to prove the existence of energy transfer phenomenon between ions.Also,the luminescence properties and energy transfer mechanism of phosphors were further explored.In the the first chapter,the rare-earth light-emitting materials are introduced.The current method of achieving white light,the development trend of white-light LEDs,the preparation methods and characterization methods of light-emitting materials and the common energy transfer phenomena in phosphors are briefly explained.In the second chapter,the experimental reagents,the experimental steps,the instruments needed to prepare phosphors and the information of the instruments used in the testing process are introduced.In the third chapter,using high temperature solid phase method,after two calcination of 850^oC and 1200^oC,KBa_0.97-xPO₄:0.03Ce³⁺,xTb³⁺,KBa_0.975-xPO₄:0.025Tb³⁺,xCe³⁺series of phosphors were prepared.On the basis of this,Sm³⁺was mixed to prepare a series of KBa_0.978-xPO₄:0.03Ce³⁺,0.002Tb³⁺,xSm³⁺phosphors.By changing the doping concentration of the Tb³⁺/Ce³⁺/Sm³⁺ions,the control of the spectrum was realized successfully.With the increase of Tb³⁺concentration,the intensity of the emission peak at 547 nm increased,and the position of phosphors in the CIE spectrum moved from the blue region to the green region,indicating the effective energy transfer of Tb³⁺/Ce³⁺ions.With the increase of Sm³⁺concentration,the position of phosphors in the CIE spectrum tends to the white region,indicating that there is Tb³⁺/Ce³⁺/Sm³⁺ions energy transfer.In the fourth chapter,the Ba_5-2xCe_xK_x?PO₄?₃F phosphors prepared by high temperature solid phase method at 1100 ^oC are introduced.It is found that the XRD diffraction peaks of the sample had a high matching degree with the standard card of Ba₅?PO₄?₃F by X-ray diffraction analysis.When the substitution concentration continued to increase,the crystal structure of the substance matched well with the standard card of Ba₃LaNa?PO₄?₃F.The prepared phosphors show a wide emission band at 410-550 nm,the strongest peak at 428 nm,and the intensity of the main peak is increasing with the increase of substitution concentration.Ba_5-2xCe_xK_x?PO₄?₃F samples are blue phosphors with stable properties and have promising applications.In the fifth chapter,Ba₃Ce_1-xK?PO₄?₃F:xTb³⁺phosphors were prepared using solid-state method under the 1100 ^oC.On this basis,Ba₃Ce_0.85-xK?PO₄?₃F:0.15Tb³⁺,xSm³⁺phosphors were synthesized by incorporation Sm³⁺.For Ba₃Ce_1-x-x K?PO₄?₃F:xTb³⁺phosphors,Ce³⁺ions characteristic peaks were at 420 nm and Tb³⁺ions characteristic peaks at 549 nm.With the increase of Tb³⁺content,the color of phosphors gradually moved from blue region to green region,which has potential application value.Ba₃Ce_0.85-xK?PO₄?₃F:0.15Tb³⁺,xSm³⁺phosphors,with the increase of Sm³⁺concentration,the characteristic peak was generated at 597 nm.Excited by325 nm,the phosphors showed a tendency to transfer from the green light region to the white light region in the CIE spectrum.In the sixth chapter,K₂Ca_1-xPO₄F:xEu²⁺phosphors were prepared using high temperature solid phase method,and the relationship between preparation temperature and luminescence properties was explored.When the doping concentration of Eu²⁺ions is 0.01 mol%,a wide emission peak appears in the range 400-520 nm and550-700 nm.When the preparation temperature is 950 ^oC,the phosphor reaches the maximum emission intensity.The phosphor prepared at this temperature is successfully prepared in the white light region of the CIE spectrum.