The formation mechanism, improved photoluminescence and LED applications of red phosphor K2SiF6: Mn4+

A red phosphor K2SiF6:Mn4+ has been prepared by etching of SiO2 in HF solution at a KMnO4 concentration as low as 0.08 mol L-1. The luminescence properties of the phosphor have been improved obviously by using KF and H2O2. The structure, morphology and thermal stability of the phosphor have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetry and differential scanning calorimetry (TG-DSC), respectively. The formation mechanismof the red phosphor K2SiF6: Mn4+ is discussed in detail. Digital images and diffuse reflection spectra showthat the phosphor is white under visible room light. An intense absorption band in the blue and a bright emission in red make the phosphor K2SiF6:Mn4+ a candidate for applications in InGaN-YAG:Ce type LEDs for high color rendering. A warm white light LED with an efficiency of 116 lm W-1 and a color rendering index of 89.9 at a color temperature of 3900 K has been obtained by fabricating YAG:Ce with K2SiF6: Mn4+ on an InGaN chip.