Research On Preparation And Properties Of Mn⁴⁺-Doped Red Phosphors

White LED, which is so called the next general lighting, is a topic of increasing interest due to their low power consumption, environment friendly, high luminous efficiency, long life, and so on. There are three kinds of way of white LED. The one of most common method is phosphorconverted LED, which encapsulation of the phosphor on a GaN layer produces white LEDs. Therefore, the properties and preparation of phosphors is receiving more and more attention. Especially red phosphor, improving the color rendering index and depressing the color temperatures of LED, become the top research of all.In this paper, red efficient phosphors K2XF6:Mn4+(X is Si or Ti) and ZnSiF6·6H2O:Mn4+, Which cheap, enrich and broad band Mn4+doped hexa-fluorometallates, has been prepared by etching of SiO2, Ti(C4H9O)4or TiO2 in HF solution with KMnO4 at room temperature or hydrothermal method. We researched the formation mechanism of red phosphors K2XF6:Mn4+(X is Si or Ti), The composition, fluorescence property, morphology and thermal stability of the as-prepared samples were also investigated by XRD, PL & PLE spectra, Raman spectrum, IR, SEM, EDS, XPS and TG-DSC. The remarkably high rendering of white LEDs was attributed to the compensation of red components by fabricating asprepared red phosphor with commercially available yellow phosphor YAG:Ce. Our specific conclusions are as follows:(1) The luminescence properties of the phosphor have been improved obviously by hydrothermal method. The KMnO4 concentration much lower than the 330 mmol?L-1used in previous work, eliminating the MnO2 phase from KMnO4 solution of low concentration;(2) We found the reactions is significant for doping Mn4+into K2SiF6 by adding of H2O2, it enhanced luminescent intensity and improved the crystallinity;(3) We researched that the color and luminescence properties of the prepared phosphors are strongly dependent on the order in which the starting materials are added;(4) We carried out ICP-AES analysis on Mn elements in the red phosphors K2 Ti F6:Mn4+, which includes that the doping concentration of Mn4+in the solid state phosphor sample was about 0.12 mol% of Ti4+;(5) Influence of the concentration of KMnO4 and HF in precursor solutions for luminescence property has been explored;(6) We studied the formation mechanism of phosphors K2XF6:Mn4+and the work of HF in reaction process;(7) ZnSiF6?6H2O:Mn4+synthesized by the one-step hydrothermal method, The H2 O molecules in the compound are structural water that coordinate Zn2+. Luminescence quenches at a temperature higher than 200 ℃, which is due to the decomposition of crystal structure.