New red-emitting phosphors AHfF:Mn (A = Rb, Cs) with a single phase have been successfully synthesized via a simple ion exchange method, and their structures and luminescence properties were investigated. It was found that Mn ions in RbHfF and CsHfF who share wide band gaps can possess broad excitation bands in the blue regions and intense red emission with internal quantum yields of 0.556 and 0.652, respectively. Meanwhile, these red phosphors exhibit high chemical and thermal stabilities. A series of LED devices with a tunable color rendering index and color temperature were fabricated with these samples which can remarkably optimize the optical performances of white light-emitting diodes (w-LEDs). These results indicate that AHfF:Mn phosphors can be promising red phosphors in w-LEDs.

Green and safe HAc acid was used as the reaction medium in the preparation process of Mn4+doped A2TiF6(X = Na, K and Cs) red phosphors, which is beneficial for the potential large scale production in the future.

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A single-phased Mn(4+) doped fluorozirconate red phosphor, K3ZrF7:Mn(4+), has been successfully synthesized. Its structure, morphology, composition and optical properties were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic absorption spectroscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy and by using luminescence decay curves. It was found that Mn(4+) ions only coordinating with seven F(-) anions in a K3ZrF7 crystal field can possess intense red emission under blue light illumination. Mixing the obtained K3ZrF7:Mn(4+) red phosphor with commercial Y3Al5O12:Ce(3+) and coating the mixture on a blue-GaN chip, obvious warm white light with a low correlated color temperature (2970 K) and a high color rendering index (Ra = 91.4 and R9 = 72) were achieved from white light-emitting diode devices.

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