A narrow-band red-emitting K2LiGaF6:Mn4+ phosphor with octahedral morphology: Luminescent properties, growth mechanisms, and applications

Abstract A narrow-band K 2 LiGaF 6 :Mn 4+ red phosphor with octahedra and self-assembled microspheres morphologies was prepared through the two-step co-precipitation and hydrothermal methods, respectively. The forming mechanism of the regular octahedral crystals and self-assembled microspheres have been explored by SEM and HRTEM. The Mn 4+ doping concentration and reaction time were optimized for improving its optical properties. The emission intensity of K 2 LiGaF 6 :Mn 4+ can still keep 87% when it worked at 150 °C, indicating its excellent thermal stability. Moreover, the as-prepared K 2 LiGaF 6 :Mn 4+ have better photoluminescence intensity and thermal stability than the previously reported K 2 LiAlF 6 :Mn 4+ , which should be attributed the optimization of morphology and structure. Especially, the slight shift of peak position of K 2 LiGaF 6 :Mn 4+ than K 2 LiAlF 6 :Mn 4+ was also analyzed in detail. Finally, the as-prepared K 2 LiGaF 6 :Mn 4+ phosphor was packaged on WLED through combining the YAG:Ce phosphor. Excellent warm white light with the CCT = 4296 K, R a  = 91, and luminous efficiency = 137.56 lm·W −1 was obtained, making it becoming the promising red phosphor candidates for white light-emitting diodes.