Investigation On Non-Rare Earth Red Phosphors SrAl₁₂O₁₉:Mn⁴⁺ For White-Lighe LED Application

Previous fluorescent material developed in commercialization light is applied to the low-pressure mercury lamp (254nm excitation) and high-pressure mercury lamp (365nm excitation). Development of semiconductor lighting technology has been constrained because of excited fluorescent material suitable for blue light emitting diode (B-LED, the emission wavelength460nm) and UV light emitting diodes (UV-LED, emitting a wavelength of365nm～400nm) is lack, especially suitable to all types of red LED excitation fluorescent materials are more lacking. The purpose of this study is to find and optimize suitable for all types of LED excitation of new non-rare earth red fluorescent material. I dentified red phosphor material SrAl12O19:Mn4+for the study, using high-temperature solid-state reaction method for the preparation of the doped system SrAl11.99-xMxO19:0.01Mn4+(M=Mg2+, Zn2+, Ge4+, x=0.00-0.12), and unsubstituted system SrAl11.91(1-y)Ga11.91yO19:0.01Mn4+(y=0.0-1.0) and Sr1-zMzAl12O19:0.01Mn4+(M=Ca2+, Ba2+; z=0.0-1.0) of the series of samples. The phase synthesis of the samples characterized useing an X-ray diffractometer and the fluorescence properties of the material were studied using fluorescence spectroscopy. The main results are concluded as follows:(1) In the doped system SrAl11.99-xMxO19:0.01Mn4+(M=Mg2+, Zn2+, Ge4+), Mg2+and Zn2+doped make emission intensity of material (λEM=658nm,2E→4A2transition) increased by about60%. The optimized doping contents are x=0.08for the Mg2+doped system and x=0.06for the Zn2+doped system, respectively. The Ge4+doping decreases the PL intensity. Electron paramagnetic resonance spectroscopy (EPR) tests indicate the role of Mg2+and Zn2+on Mn4+doping played a charge compensation of:MO+MnO2(?)MAI+MnAl+30OX (M=Mg,Zn).(2) The whole range solid solutions are formed in Ga3+replaces Al3+system, when small amount of Ga3+is doped (Ga3+content varies fromy=0.0004-0.004), the PL intensity may increase, e. g. at y=0.008, the PL intensity increases about13%. Whereas when the y value further increases, the PL intensity dramatically decreases.(3) The PL properties of the Sr site replaced systems Sr1-zCazAl11.91O19:0.01Mn4+,0.08Mg2+and Sr1-zBazAl11.91O19:0.01Mn4,0.08Mg2+were studies. In both of the systems, only limited rather than the whole range solid solutions form. In the system Sr1-zCazAl11.91O19:O.OlMn4+,0.08Mg2+, the solid solutions appear in the ranges0.0<z<0.8and0.9<z<1.0, and the two-phase range is narrow in the range0.8<z<0.9. While in the system Sr1-zBazAl11.91O19:0.01Mn4+,0.08Mg2+, the two-phase range become wider,0.1<z< 0.8and the solid solutions appear only in the narrow ranges0.0<z<0.1and0.8<z<1.0. The PL intensity increased with the Ca2+content, but for the Ba2+replacing system.It is believe that the optimized SrAl12O19:Mn4+would be a potential red phosphor candidate for improving the color rendering of the white LEDs.