Room-temperature synthesis and optimized photoluminescence of a novel red phosphor NaKSnF6:Mn4+ for application in warm WLEDs

A kind of red-emitting phosphor NaKSnF6:Mn4+' (NKSF:Mn) has been obtained from NaF and KF with a certain molecular ratio in HF solution at room temperature. The phosphor NKSF: Mn exhibits superior optical properties including high color purity with narrow-band emissions as well as better chromaticity coordinates compared to the red phosphors Na2SnF6:Mn4+ (NSF:Mn) and K2SnF6 center dot H2O:Mn4+ (KSFH: Mn). The composition and structure of NKSF: Mn have been identified by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The formation mechanism of NKSF: Mn is discussed and the morphology, thermal stability, and optical properties of NKSF: Mn have been investigated. The luminescence intensity of NKSF: Mn has been improved by optimizing synthetic parameters. A white light-emitting diode (WLED) fabricated using a blue GaN chip, a yellow YAG:Ce phosphor, and the as-prepared red phosphor NKSF: Mn exhibits superior warm white light with a color rendering index (CRI) of 90.3 at a correlated color temperature (CCT) of 3746 K.