Rare Earth Activated Sr₃Al₂O₆ Host Phosphors Used For InGaN Chip Base Light Emitting Diodes

The development of white light-emitting diode(WLEDs) induces a newly fast-growing lighting revolution soon after the microelectronics revolution in semiconductor industry.With the advantages of small volume,vibration-resistance,fast response,long lifetime and free pollution,WLEDs as the fourth-generation light source are expected to replace traditional incandescent,fluorescent and High-Intensity gas Discharge lamps.Of presently existing problems,besides luminous efficiency and lifetime of WLED,an important parameterr,color rendering index(CRI),of present InGaN/YAG:Ce WLED pattern is highly needed to improve by developing new non-sulfide base red phosphors,which could be easily excited by blue or ultraviolate blue light in higher efficiency.This research work is focusing on a red and white phosphor with stoichiometric host Sr₃Al₂O₆,including prearation,microstructure and spectrum properties.Innovative results achived in this work include:â… .Orange phosphor Sr₃Al₂O₆:Eu,Dy³⁺ phosphor excited by blue light have been successfully prepared by spray pyrolysis method from composite sols with nano-scale boehmite as Al resource,reliazing a non-metallic ethylate sol-gel preparation route.â…¡.The photoluminescence spectra of as-received Eu²⁺ doped-Sr₃Al₂O₆ phosphors show that the phosphors have the broad excitation band from 400 nm to 500 nm,which match well with the emission wavelength of InGaN-chips,and the emission band peaks at 595 nm, possibly resulting in improvement of color rendering index(CRI) of WLEDs.â…¢For Sr₃Al₂O₆:Eu,Dy³⁺ phosphor,orange light is ascribed to luminous centre Eu²⁺. The ratio of relative intensities of emission peaks of Eu²⁺ and Eu³⁺ ions in crystal structure of Sr₃Al₂O₆ have been evaluated to reveal that partial replacement of cations by Zn²⁺ and the further introduction of Sr²⁺ vacancies into lattice contribute to reduction of Eu³⁺ to Eu²⁺ inducing enhancement of the luminous efficiency.â…£.By using high-temperature solid-state method,single-host white-light Sr₃Al₂O₆:Dy³⁺ phosphor powders have been obtained.Under the 350 nm excitation the phosphors emit yellow light(578nm) and blue light(484 nm) simultaneously,corresponding to transitions from ⁴F_9/2 to ²H_13/2 and ²H_15/2 within 4t⁹ configuration of Dy³⁺,respectively.The same decay rate of two kind of light are verified to combine the white light uniformly,providing the possibility for fabricating long aftergolow WLED with color stability during decay.â…¤.The great difference of characteristic luminous properties of Dy³⁺ with respect to Ca, Sr and Ba in aluminate host has been observed.As for this we interpret linkage form of polyhedronal[AlO₄]in the Ba₃Al₂O₆ host is different from that in the Sr₃Al₂O₆ host.