A new red phosphor BaGeF₆:Mn⁴⁺prepared by a hydrothermal route shows intense red emission under blue light excitation, which may find application in warm white LED devices.

A new red phosphor Cs ₂ TiF ₆ :Mn ⁴⁺ has been prepared by a facile cation exchange route, which can absorb the broad blue band and emit intense red light efficiently, and can be a potential candidate for application in indoor lighting WLEDs.

Red-emitting phosphors Na₂XF₆:Mn⁴⁺ (X = 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 Na₂SiF₆:Mn⁴⁺ shares bright red emission under blue light excitation, and its CIE coordinates are x = 0.684, y = 0.315, which are close to the NTSC (National Television Standard Committee) standard values for red (x = 0.67, y = 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 Na₂SiF₆:Mn⁴⁺ maybe serve as a red-emitting phosphor for application in warm WLEDs.

A new Mn⁴⁺doped hexafluorozirconate complex, Cs₂ZrF₆:Mn⁴⁺, was prepared successfully through a cation exchange route. With introduction of this phosphor, theR_aandT_cvalues of a YAG type WLED can be significantly improved, indicating its potential application for warm white lighting.

BaTiF ₆ :Mn ⁴⁺ : a fluoride-based red phosphor with a sharp emission line and broad absorption in the blue region used for warm WLEDs.

A single-phased K ₃ ZrF ₇ :Mn ⁴⁺ has been successfully synthesized, in which Mn ⁴⁺ playing as the luminescent center to absorb blue light and emit red light. Obvious warm white light can be observed from the WLED based on this red phosphor.