Luminescence behaviour of Mn4+ ions in seven coordination environments of K3ZrF7

Abstract

A single-phased Mn⁴⁺ doped fluorozirconate red phosphor, K₃ZrF₇:Mn⁴⁺, 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 Mn⁴⁺ 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:Mn⁴⁺ red phosphor with commercial Y₃Al₅O₁₂:Ce³⁺ 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 (R_a = 91.4 and R₉ = 72) were achieved from white light-emitting diode devices.