The Construction Of Three Novel Fluoride Red Phosphors For LED Application Based On Mn⁴⁺ Luminescence

White light emitting diode?WLED?,the fourth generation of solid-state lighting source,have many advantages such as small size,long lifetime,good stability,energy saving and environmental protection.At present,the commercial WLED mainly consists of GaN or InGaN blue chip with high quantum efficient yellow phosphor Y₃Al₅O₁₂:Ce³⁺.However,such LED devices exhibit high color temperature?>4500K?,low color rendering index?<80?due to the lack of red component,which seriously limit the application for indoor lighting and backlight display.Adding a certain proportion of red component is an effective way to solve the above problem.Mn⁴⁺doped fluoride?oxyfluoride?red fluorescent material have already become an ideal material due to its cheap raw material,simple and environmentally friendly synthesis method,good chemical stability and high luminous efficiency.In this work,three red phosphors for LED were studied.The main contents are as follows:?1?The BaTiOF₄ oxyfluoride material with the same morphology was synthesized by hydrothermal method and the microstructure of the synthesized samples under different reaction conditions were studied.The material were characterized by XRD,EDS and IR.The results showed that the microstructure was uniform and regular,indicating that PEG6000 plays an important role in inducing the orderly growth of structural materials.?2?A novel red fluorescent material BaTiOF₄:Mn⁴⁺was synthesized by two-step method.In the first step,the host was synthesized by hydrothermal method with distilled water as the reaction solvent.Next,anhydrous ethanol and a very small amount of HF were used as the solvent for the exchange of Mn⁴⁺to Ti⁴⁺at room temperature.The phase structure,morphology,chemical thermal stability and optical properties of the synthesized materials were investigated in detail.The results show that BaTiOF₄:Mn⁴⁺red phosphor is an efficientred fluorescent material that can be used in LED backlight display.?3?A novel Cs₂NaAl₃F₁₂:Mn⁴⁺red phosphor was synthesized.The study shows that the dopant of Mn⁴⁺ions in Cs₂NaAl₃F₁₂2 leads to the cation vacancies near the octahedron[MnF₆],which exhibits a strong ZPL emission peaking at 623 nm.The red color purity of Cs₂NaAl₃F₁₂:Mn⁴⁺is above 99%.The application of Cs₂NaAl₃F₁₂:Mn⁴⁺red phosphor in white LED can improve the performance of LED devices.?4?The Cs₂NaAlF₆:Mn⁴⁺red phosphors were synthesized by ion exchange method.In the crystal lattice of Cs₂NaAlF₆:Mn⁴⁺,there are two crystal lattice positions of Al?I?and Al?II?.The Cs₂NaAlF₆:Mn⁴⁺has a very strong ZPL?625 nm?emission closed to the ideal red position,which results in the Cs₂NaAlF₆:Mn⁴⁺phosphor applied in LED device showed low color temperature and high color rendering index values for LED application.In summary,the crystal structure,morphology composition and optical performance of three fluoride materials were carefully studied in this paper so as to provide ways to improve the performance of LED devices.