Design, preparation, and optical characteristics of novel red phosphors A2NaInF6:Mn4+ (A = K and NH4) for improving the performance of WLED

Novel Mn⁴⁺-activated red light-emitting phosphors, A₂NaInF₆:Mn⁴⁺ (A = K and NH₄), have been designed and obtained through co-precipitation method. The phase identification, morphology and composition have been systematically investigated via X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometers (EDS), respectively. The excitation peaks of the red phosphors K₂NaInF₆:Mn⁴⁺ and (NH₄)₂NaInF₆:Mn⁴⁺ are located at 300–550 nm, which means that (K,NH₄)₂NaInF₆:Mn⁴⁺ can be applied in blue and ultraviolet chips. Excited by the blue light, the phosphors A₂NaInF₆:Mn⁴⁺ (A = K and NH₄) exhibit red light emitting at 600–650 nm. The influence of reaction time, starting materials and the doping amounts of Mn⁴⁺ on the crystal structure and optical characteristic has been investigated. The temperature-dependent fluorescence results of K₂NaInF₆:Mn⁴⁺ samples have been also provided. The fabricated WLED with colour rendering index (R_a = 83.4) and low colour temperature (4444 K) is attained by using the prepared K₂NaInF₆:Mn⁴⁺ product. Therefore, the red light-emitting A₂NaInF₆:Mn⁴⁺ (A = K and NH₄) phosphors could be regarded as good candidates for improving the performance of WLED.