Synthesis And Luminescent Properties Of Small-sized K₂SiF₆:Mn⁴⁺ Phosphor

K₂SiF₆:Mn⁴⁺red phosphor plays a vital role in improving the color of white LEDs.Phosphor with small particle size and uniform size distribution can directly improve the light efficiency,light color uniformity and yield of white light LEDs.The emergence of Mini-LED and Micro-LED also makes the nano-sized K₂SiF₆:Mn⁴⁺have important application scenarios.At the same time,K₂SiF₆:Mn⁴⁺hydrolyze easily in the hot and humid environment.Therefore,to study the growth mechanism of K₂SiF₆:Mn⁴⁺and to develop a small particle size and high stable K₂SiF₆:Mn⁴⁺has great application value.Firstly,this work explored the influence of main parameters of the co-precipitation to synthesize K₂SiF₆:Mn⁴⁺in aqueous solution on the particle size and optical performance.And explored the growth mechanism of K₂SiF₆:Mn⁴⁺in liquid phase.Secondly,Using precipitation in organic solution（ethanol/acetic acid）and efficient ion exchange synthesized nano K₂SiF₆:Mn⁴⁺.Finally,experiments were conducted to improve the water resistance of K₂SiF₆:Mn⁴⁺by hydrothermal post-treatment,and the effect of glucose and sulfuric acid on water resistance was studied.1.The main parameters on co-precipitation in aqueous solution was studied.The results show that the best synthesis temperature is 31℃and the doping amount of Mn⁴⁺is 10.3%.The aging process can affect the phosphor particle size,and the row material concentration can significantly affect the phosphor particle size.When the molar ratio of K and Si raw material is increased from1:0.5 to 6:1,the mean particle size decreased from 12.40μm to 2.44μm.2.A possible growth model of K₂SiF₆:Mn⁴⁺in the liquid phase is proposed:it grows in the liquid phase mainly through dissolution/recrystallization and mass transfer.Secondly,when the growth of K₂SiF₆:Mn⁴⁺is hindered,it tends to form a hexahedron morphology with（100）dominates.But in an environment suitable for growth,a truncated hexahedron morphology with（111）dominates will be formed.3.K₂SiF₆:Mn⁴⁺nano-phospher were prepared by precipitation using organic solution（ethanol/acetic acid）and efficient ion exchange method.The results show that nucleation rate is the dominant of particle size which depend on reaction temperature due to the blocking of growth in the organic solution.Higher reaction temperature will leading smaller particle size,and the mean size of K₂SiF₆:Mn⁴⁺prepared at 70℃is 200nm.4.The water resistance of phosphors can be significantly improved through hydrothermal post-treatment.After six days of degradation treatment under 85%humidity and 85℃,the IQY of untreated phosphor dropped to 24.0%but after treatment was maintain 65.8%.Because hydrothermal post-treatment can lead the rearrangement of atoms,and dissolved/recrystallization can produces a Mn-poor shell on the surface,which can both improve water resistance of phosphor.5.Glucose and sulfuric acid can improve the effects of hydrothermal post-treatment.The results show that the hydrolyzate of glucose can passivate the surface of phosphor,and sulfuric acid can make Mn-poor shell thicker.Under the experimental conditions is 0.06g glucose and KHF_2mol/KSFM_mol=16:1,IQY of the post-treated phosphor can maintain 97.0%after degraded at 85%humidity and 85℃for six days.