Morphology controllable BaNbF5.5(OH)1.5:Mn4+ red phosphor with strong zero phonon line for WLED application

A hydroxy fluoride red phosphor BaNbF5.5(OH)1.5:Mn4+ with dual morphology was designed and manufactured by co-precipitation strategy. The crystal phase structure, controlled morphology and photoluminescence performances were systematically investigated. The Mn4+ non-equivalent doped hydroxy fluoride phosphor has similar luminescence performance to fluoride phosphors, and it is worth noting that it presents a very strong zero phonon line (ZPL) at ∼629 nm at blue light excitation and has high color purity (98.5%). Crystal field intensity (Dq), Racah parameters (B and C) and nephelauxetic effect ratio parameter β1 of the sample were calculated and analyzed, the results indicate that the BaNbF5.5(OH)1.5 matrix provides a strong crystal field environment for Mn4+. The effects of the experimental conditions on the morphology of the phosphors were analyzed, and optimal synthetic conditions were determined. Because of the short fluorescence decay lifetime (τ < 4 ms), this red phosphor may be a prospective red emitting candidate for backlight displays. Moreover, the as-prepared BaNbF5.5(OH)1.5:Mn4+ red phosphor possesses distinguished UV light-induced stability. Thermal stability and hydrophobic stability of the phosphor were analyzed. Thanks to the strong ZPL, WLED device prepared with this phosphor can produce warm white light and show remarkable photoelectric properties, with a color rendering index (CRI, Ra) of up to 92.5 and a correlated color temperature (CCT, Tc) as low as 3944 K. The results indicate that the red phosphor BaNbF5.5(OH)1.5:Mn4+ has application possibilities in WLED illumination and display backlighting.