Preparation And Performance Optimization Of Mn⁴⁺ Activated Fluoride Red Phosphor

LED has replaced the traditional incandescent lamp,as a new generation of mainstream lighting source.One of the key factors of LED luminous performance is the red phosphor,so it is particularly important for the selection of red phosphor and the optimization of performance.Mn⁴⁺activated fluoride red phosphor has a broad blue excitation peak near 460 nm,which can be well matched with commercial LED blue chips.And because the Mn⁴⁺activated fluoride red phosphor has a sharp red narrow band emission near 636 nm,it does not reabsorb with the yellow phosphor,so it is an ideal red phosphor for LED.However,there are several problems that need to be solved urgently for Mn⁴⁺activated fluoride red phosphor.The first is that its luminous performance is affected by the preparation method,and the luminous intensity of the phosphor obtained by different process conditions is different;The second is its poor water resistance,easy to decompose in water;Finally,it has a lower luminous intensity than commercial green and yellow phosphors.In order to solve these problems,we used different preparation methods to synthesize fluoride red phosphor,and determined the best process conditions;On this basis,the water resistance of K₂TiF₆:Mn⁴⁺phosphor was optimized,and the luminous intensity of K₂SiF₆:Mn⁴⁺phosphor was optimized.The research content and results are as follows:1.BaTiF₆:Mn⁴⁺,K₂SiF₆:Mn⁴⁺,K₂TiF₆:Mn⁴⁺phosphors were synthesized by hydrothermal method,co-precipitation method,and ion exchange method,respectively.The effects of different preparation methods on the luminous intensity of fluoride phosphors were explored,and the best process conditions were determined:The best HF dosage of BaTiF₆:Mn⁴⁺prepared by the hydrothermal method is 25 mL,and the best doping amount of Mn⁴⁺is 4 mol%when preparing BaTiF₆:Mn⁴⁺phosphor by co-precipitation method;Co-precipitation method to prepare K₂SiF₆:Mn⁴⁺phosphors,the best Mn⁴⁺doping amount is 2.9 at%,the best KF-HF concentration is 0.4 g/mL;The optimal Mn⁴⁺doping amount of K₂TiF₆:Mn⁴⁺phosphor prepared by ion exchange is 2.7 at%.2.We adopted a simple one-step method to successfully coat SiO₂ and CaF₂ on the surface of K₂TiF₆:Mn⁴⁺,which improved the stability of K₂TiF₆:Mn⁴⁺phosphor:After coating SiO₂,the stability of K₂TiF₆:Mn⁴⁺phosphor has been improved.After the alcohol and water mixed solution is soaked,the intensity of K₂TiF₆:Mn⁴⁺/SiO₂phosphor remains 49.3%,while the intensity of K₂TiF₆:Mn⁴⁺phosphor remains only25.1%;After coating CaF₂,the stability of the phosphor has been significantly improved.After immersion in a mixed solution of alcohol and water for 24 h,the intensity of K₂TiF₆:Mn⁴⁺/CaF₂ phosphor decreased by only 13.6%,while the intensity of K₂TiF₆:Mn⁴⁺phosphor decreased by 93.2%,While the luminous intensity is 1.03times of the original.3.Using a simple two-step method,g-C₃N₄,CaF₂,CaF₂:Eu³⁺and K₂SiF₆:Mn⁴⁺phosphor were successfully compounded to increase the luminous intensity of the phosphor:The luminous intensity of K₂SiF₆:Mn⁴⁺/g-C₃N₄ phosphor is 1.43 times that of K₂SiF₆:Mn⁴⁺,which is due to increased charge transfer efficiency of phosphor and energy transfer;The luminous intensity of K₂SiF₆:Mn⁴⁺/CaF₂ is 2.83 times that of K₂SiF₆:Mn⁴⁺phosphor.This is due to the formation of an anti-reflection layer on the surface of the phosphor,which improves light absorption and suppresses the quenching effect of the surface OH group on the reduction;The luminous intensity of K₂SiF₆:Mn⁴⁺/CaF₂:Eu³⁺phosphor is 3.78 times that of K₂SiF₆:Mn⁴⁺,and the excitation emission range is significantly widened.