Fluorescence enhancement mechanism in phosphor CaAl12O 19:Mn4+ modified with alkali-chloride

Abstract

CaMAl12 - xO19:xMn4+ (M is one or more of K+, Na+, Li+) materials were prepared by a combustion method in air atmosphere. The Mn concentration, the influence of one or more alkali-chloride on luminescence properties, crystal phases and surface morphology of the samples were investigated. The fluorescence intensity of CaAl11.98O19:0.02Mn4+ modified by combining three kinds of alkali-chloride can be enhanced by three times. Blue shift of CaMAl12 - xO19:xMn4+ luminescence is explained from the point of view of enhancing electron cloud deformation after doping. Alkali metal ions were beneficial to form hexagonal CaAl12O 19 while there was certain inhibition to other peak strengths. The mechanism is the coexistence of alkali-chloride replacing Al3+ or Ca2+ instead of Mn2+ based on the difference of cation radius, this would increase the luminous centre of Mn4+ and provide charge compensation at the same time. The size of red phosphors was 5-10 μm, which is useful for light emitting diode applications. © The Institution of Engineering and Technology 2013.