In this work, Cs2ZrF6:Mn 4+ red phosphor, a novel and efficient supplement for commercial Y3Al5O12:Ce 3+ type white light-emitting diodes (WLEDs) has been successfully fabricated in large scale through cation exchange method using K2MnF6 as Mn 4+ source at ambient temperature. The crystal structure and morphology were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive Xray spectroscopy (EDS) in details. It is well crystallized into single-phase with particulate morphology and presents sharp red emissions under blue light illumination. From the aspects of Ra and Tc view, the optical performance of the WLED made from Cs2ZrF6:Mn 4+ red phosphor supplement is significantly improved and can be used for indoor lighting application.
Red-emitting phosphors Na 2 XF 6 :Mn 4+ (X ¼ Si, Ge, Ti) were synthesized by a simple co-precipitation method. The crystal structure, morphology and composition of as-prepared phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS) and atomic absorption spectroscopy (AAS). Their optical properties were investigated by photo-luminescent spectra (PL), diffuse reflectance spectra (DRS), and the luminescence decay curves. These phosphors exhibit broad excitation band in blue regions and intense emission in red regions with high color-purity. The sample Na 2 SiF 6 :Mn 4+ shares bright red emission under blue light excitation, and its CIE coordinates are x ¼ 0.684, y ¼ 0.315, which are close to the NTSC (National Television Standard Committee) standard values for red (x ¼ 0.67, y ¼ 0.33). The white-light-emitting diodes (WLEDs) fabricated with this phosphor emits intense warm white-light with lower color temperature (3930 K) and higher color rendering index (92.3). The above results indicated that red phosphor Na 2 SiF 6 :Mn 4+ maybe serve as a red-emitting phosphor for application in warm WLEDs.
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