Preparation Of Rare-earth Red Luminescent Materials And Study On The Luminescence Properties

Human modern lighting has experienced incandescent lamps,fluorescent lamps,high gas discharge lamps,and the current white light LED.The emergence of rare earth luminescent materials has promoted the development of modern lighting of human beings.The rare earth luminescent materials with aluminate and silicate have excellent physical and chemical properties,and have attracted wide attention.Because of the fact that the efficiency of red LED phosphors has been reduced too fast and affects their later usage,the red phosphor with high efficiency and long life has been widely sought.Me₃Al₂O₆:Eu³⁺?Me=Ca,Sr,Ba?phosphor is a new type of red phosphor found in recent years.The absorption of Eu³⁺in the near ultraviolet region can emit the strongest peak of 618nm.akermanite Me₂MgSi₂O₇?Me=Ca,Sr,Ba?has been widely concerned because of its excellent chemical and thermal stability.In this paper,Ca₃Al₂O₆:Eu³⁺and Ca₂MgSi₂O₇:Eu³⁺phosphor were synthesized by high temperature solid phase method.The influence of doping concentration of Eu³⁺on the luminescent properties of Ca₃Al₂O₆:Eu³⁺phosphors and Ca₂MgSi₂O₇:Eu³⁺phosphors was discussed.The effects of Y³⁺,sensitizers Ce³⁺and Dy³⁺on the luminescent properties of Ca₃Al₂O₆:Eu³⁺were analyzed.The main research results are as follows:?1?The Ca₃Al₂O₆:Eu³⁺phosphors are prepared by high temperature solid-state method.Because of the crystal water contained in the raw material,the gas released during the calcination process made the samples appear porous.The effect of Eu³⁺doping concentration on the luminescence properties of Ca₃Al₂O₆:Eu³⁺phosphors are investigated.It is found that the emission peak of the sample is the strongest when the doping concentration is 2.5%.Under the excitation of 395nm near ultraviolet light,the sample can emit stronger red light.The Ca₃Al₂O₆:Eu³⁺phosphors with different Eu³⁺doping concentration have no uniform morphology,and there are agglomeration phenomena.When the doping concentration of Eu³⁺is low,the samples only grow towards the flaky shape.When the doping concentration of Eu³⁺is greater than 5%,the sample tends to rod growth.At this time the flake and the bar form coexist.?2?The addition of Y³⁺,Dy³⁺and Ce³⁺can make Ca₃Al₂O₆:Eu³⁺phosphors emit red light of618nm,but the emphasis is different.The addition of Y³⁺and Dy³⁺can improve the luminescent properties of Ca₃Al₂O₆:Eu³⁺phosphors.That is,stronger red light can be emitted under the excitation of395nm wavelength,and the luminescence intensity is increased by twice and once,respectively.There is a phenomenon of energy transfer between Dy³⁺and Eu³⁺.The addition of Ce³⁺can enhance the intensity of 465nm excitation peak.Similarly,when 465nm wavelength is excited,the sample can emit stronger red light,and there is energy transfer between Ce³⁺and Eu³⁺.Therefore,the Ca₃Al₂O₆:Eu³⁺red phosphors added by Y³⁺and Dy³⁺are expected to be used in the white light LED.?3?Different Eu³⁺doping concentrations of Ca₂MgSi₂O₇:Eu³⁺can emit bright red light.When the doping concentration is 3.5%⁴.5%,the intensity of the emitted light reaches the maximum value at the excitation wavelength of 395nm.At this time,the intensity exceeds the range of the instrument,and the intensity is over 10000.Therefore,the best doping concentration is 3.5%⁴.5%.When the doping concentration is more than 6%,the concentration quenching of the sample appears.The Ca₂MgSi₂O₇:Eu³⁺with different Eu³⁺doping concentration has a unified morphology,all of which are stacked blocks.With the increase of Eu³⁺doping concentration,there is almost no change in the morphology of the samples.That is,the doping concentration of Eu³⁺has little effect on the morphology of the samples.