Synthesis of K2XF6:Mn4+ (X = Ti, Si and Ge) red phosphors for white LED applications with low-concentration of HF

Abstract

Red phosphors K2XF6:Mn4+ (X=Ti, Si and Ge) have been successfully synthesized by one-pot chemical co-precipitation method in low HF concentration with the addition of acetic acid glacial. The crystal structure and morphology of these phosphors were characterized by powder X-ray diffraction (XRD), scanning-electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) in detail. Their optical properties were investigated by excitation and emission spectra, diffuse reflectance spectra, and decay curves. These phosphors exhibit intense red emission with high color-purity under blue light excitation. Finally, the applications on the white-light-emitting diodes (WLEDs) of the as-prepared sample were investigated. The WLEDs fabricated with K2XF6:Mn4+ display warm white light with lower color temperature (Tc<4000K) and higher color rendering index (Ra>80).