Controlled Synthesis And Luminescent Properties Of Dy³⁺,Sm³⁺,Tm³⁺,Bi³⁺ Doped Luminescent Ca₂Al[AlSiO₇] Material

Rare earth phosphors are rather important as a kind of functional materials,which have found wide applications in artificial lighting and displaying.Silicates are considered as ideal hosts for rare earth phosphors owing to their excellent properties,such as abundant raw materials,easy and adaptable synthesis methods,stable crystal structure,ease of the adjustment in their structures and compositions,stable thermal and chemical properties.Versatile luminescent properties can be obtained by doping rare earth ions in silicate hosts.In present work,a systematic research was carried out on the processing methods,luminescent properties,spectral tuning and the application in white LEDs of the rare earth silicate phosphors.In this paper,we have carried on the frame like sodalite silicate luminescent materials Dy³⁺/Sm³⁺,Dy³⁺/Tm³⁺,Tm³⁺/Bi³⁺doped and co-doped detailed research of light-emitting characteristics of them.Their structures,luminous performance,color purity and decay curves were characterized by using the X-ray diffractometer（XRD）,luminous fluorescence spectrometer,The International Commission on illumination（CIE）standard colorimetric system,and the Steady/transient testing methods.1.A series of luminescent phosphors Ca₂Al[Al SiO₇] co-doped with Dy³⁺,Sm³⁺were synthesized by the solid-state reaction.The crystal structure and luminescent properties of samples were characterized by XRD and PL.Test results indicate that the Synthesis of luminous powders form pure phase of the luminum melilite phosphors;The Analyzed of optimal doping concentration and the energy transfer of the between to Dy³⁺,Sm³⁺ions;In the Dy³⁺and Sm³⁺co-activated samples,The experiment proved that,the radiation energy transfer mode is a resonance transmission.Dy³⁺,Sm³⁺ co-doping samples in blue and yellow light luminous intensity were decreases,red band luminous intensity.Two kinds of rare earth ions in the best concentration of the sample color coordinates（0.3584,0.2867）with the standard white light color close to coordinate and good color purity.2.A series of tunable phosphors Ca₂Al[AlSi O₇]:Dy³⁺,Tm³⁺prepared utilizing a high-temperature solid-state reaction method.The phase structure,luminescence properties,energy-transfer mechanism from the Tm³⁺ to the Dy³⁺ ions and CIE coordinates were investigated in detail.Test report that,the phosphor has potential application for near-UV emitting diodes.Tm³⁺ ions in the UV excitation of the blue emission is likely to be able to effectively improve Ca₂Al[AlSiO₇]:Dy³⁺ phosphor dueto lack of blue part of slant yellow light emission.In addition,the PL and PLE results demonstrate that there a significant energy transfer from Tm³⁺to Dy³⁺.The lifetime decay results further verified that the energy-transfer mode of Tm³⁺→Dy³⁺ is attributed to the non radiative energy-transfer.Energy transfer effitiency was 40%.Adjusting the concentration of Dy³⁺/Tm³⁺ions,the Ca₂Al[AlSiO₇] phosphor can get the best color concentration（0.3104,0.3321）in the white light region.3.A blue phosphor Ca₂Al[AlSiO₇]:Bi³⁺,Tm³⁺ was synthesized by solid-phase reaction and its phase structure,Photo luminescence properties were characterized by X-Ray powder diffraction（XRD）,PL spectrem and CIE,respectively.The influence of Bi³⁺ and Tm³⁺ doping concentration on luminescence properties was also studied.The results indicate that Bi³⁺and Tm³⁺act as sensitizer and activator into the Ca₂Al[Al SiO₇].Their optimum doping concentrations are 2% and 0.6%（molar fraction）,respectively.The emission spectra of Ca₂Al[AlSiO₇]:Bi³⁺ powder phosphors at 405nm ³P₀→¹S₀.The emission peak of Ca₂Al[AlSiO₇]:Tm³⁺ with 455 nm which ¹D₂→³H₄.The optimized Tm³⁺ mole fraction is 1.5%,the luminescent intensity of the phosphor Ca₂Al[AlSiO₇]: Bi³⁺ increases up to1.8 times than that of phosphors without doping Bi³⁺.