Rapid Preparation And Performance Research Of Fluoride Red Phosphor

White light-emitting diodes（LEDs）have attracted much attention due to the advantages of energy saving,environmental protection and high efficiency,they are known as the new generation of green solid light sources in the 21st century.At present,commercial white LEDs are packaged by a combination of"blue LED chips+Y₃A_l5O₁₂:Ce³⁺yellow phosphors".However,due to the lack of red light components in the spectrum,the device has the disadvantages of low color rendering index（CRI/Ra）and high color temperature（CCT）,so it is particularly important to explore high-performance red phosphors.In recent years,Mn⁴⁺-doped fluoride red phosphors have attracted public attention due to their low cost,high luminous efficiency and good thermal stability.The current research on this type of phosphor is mainly focused on exploring more new types of high-efficiency phosphors,reducing or replacing the use of HF as the raw material,and improving the low water resistance of such phosphors.At present,the preparation of most fluoride red phosphors requires the precursor K₂Mn F₆,while the preparation of the precursor K₂Mn F₆requires the use of a large amount of HF.At the same time,the fluoride red phosphor prepared by K₂Mn F₆is on the surface of the powder in a humid environment.The[Mn F₆]^2-group will decompose into Mn O₂and Mn（OH）₄,causing fluoride phosphors to damage the structure of the sample and reduce the optical performance,which limits its application in high-performance white LEDs and wide color gamut displays.Therefore,in view of the above situation,this paper aims to explore a new type of highly waterproof KHF₂:Mn⁴⁺fluoride red phosphor that can not only reduce the amount of HF but also replace the precursor K₂Mn F₆.The main contents and results of the research are as follows:（1）Structure analysis and luminescence performance research of KHF₂:Mn⁴⁺red phosphor:We synthesized a new environmentally-friendly water-soluble KHF₂:Mn⁴⁺luminescent material using a simple one-step rapid method（only a small amount of HF）.The result analysis found that the Mn⁴⁺in the KHF₂:Mn⁴⁺red phosphor exists in the gaps of the KHF₂matrix,which has unique interstitial luminescence characteristics,and after Mn⁴⁺enters the gaps of the KHF₂matrix,the surrounding K⁺and F^-are slightly spatially different.mobile.In addition,XPS results verify that only positive tetravalent Mn exists in the substance;the TEM and SEM results show that the substance has good crystallinity,the particle surface is smooth,and the particle size is about 6-10μm;the PL spectrum shows the red emission of KHF₂:Mn⁴⁺,which is located at～602.2,611.2,615.6,633.2,637.2 and650.0 nm,respectively.It has zero thermal quenching characteristics and a good quantum efficiency of 65%.（2）Preparation of fluoride red phosphor with Mn⁴⁺doped KHF₂as the precursor and luminescence performance study:KHF₂:Mn⁴⁺phosphor as a green ion exchange luminescent material not only has unique gap luminescence performance,but also can be dissolved in pure water In order to produce anion[Mn F₆]^2-complex,used to prepare Mn⁴⁺activated fluoride red phosphor,such as K₂Ge F₆:Mn⁴⁺,K₂Si F₆:Mn⁴⁺,K₂Ti F⁶:Mn⁴⁺,etc.,which become potential candidates to replace K₂Mn F₆,which is activated by Mn⁴⁺Fluoride phosphors to develop a green route.We prepared K₂（H）Ti F₆:Mn⁴⁺（KHTFM）and K₂Ti F₆:Mn⁴⁺（KTFM）phosphors using KHF₂:Mn⁴⁺and K₂Mn F₆precursors as Mn sources,respectively.The reason why the proton-containing KHTFM phosphor has water resistance is that the parasitic[HMn F₆]^-complex that is shed from KHF₂:Mn⁴⁺and exists in the interstitial site is transferred to the K₂Ti F₆matrix through ion exchange to form a KHTFM with a rigid structure,thereby improving the sample’s performance.Water resistance and thermal stability.Through comparative analysis,after immersing in distilled water for 180minutes,the KHTFM sample retains at least 92%of the original emission value,while the luminous intensity value of the non-waterproof phosphor KTFM only maintains 23%.Therefore,these findings indicate that the KHF₂:Mn⁴⁺precursor brings protons into the fluoride red phosphor and can play a waterproof role.（3）The influence of X（X=Ti,Ge,Si）doped ions on the luminescence performance of KHF₂:Mn⁴⁺red phosphor and its devices:We use ion doping methods,by adding K₂XF₆（X=Ti,Ge,Si）solution to improve the luminous performance of KHF₂:Mn⁴⁺phosphor.The study found that dropping too much K₂XF₆solution will produce K₂XF₆（X=Ti,Ge,Si）impurity phase;when dropping 0.3 ml K₂XF₆（X=Ti,Ge,Si）solution,KHF₂:Mn⁴⁺phosphor The luminous intensity reached the maximum,increased by 50%,40%and 38%respectively,and when Ti and Ge were introduced into KHF₂:Mn⁴⁺,zero phonon lines appeared in the emission spectrum of the sample.On the basis of the above optimization scheme,we discussed the doping amount of Mn⁴⁺concentration in the sample,and found that the increase of Mn⁴⁺content does not change the host structure,and the luminescence performance of the phosphor also shows a trend of first increasing and then decreasing.In addition,we applied synthetic YAG,KHF₂:0.197%Mn⁴⁺and KHFM4-4 red phosphors to white LED devices,and packaged WLED1-3 with different color temperatures.Driven by a drive current of 20 m A,the correlated color temperature（CCT）and color rendering index（Ra）of WLED2 and WLED3 are improved compared to WLED1,but the luminous efficiency is slightly reduced.It shows that KHF₂:Mn⁴⁺phosphor is a promising red phosphor in WLED indoor lighting applications.