Red-emitting phosphors APF6:Mn4+ (A = Cs+, Rb+, K+): synthesis, luminescence properties and application in solid-state lighting

Abstract

A series of APF₆:Mn⁴⁺ (A = Cs⁺, Rb⁺, K⁺) phosphors with single phases were obtained via a simple ion exchange method. These phosphors can exhibit red emission with a broad excitation band in the blue region. The optimized concentration of Mn⁴⁺ in APF₆:Mn⁴⁺ was determined. The Racah parameters B and C of Mn⁴⁺ in APF₆:Mn⁴⁺ were also calculated. The results indicate that Mn⁴⁺ in CsPF₆:Mn⁴⁺ experiences the weakest crystal field among APF₆:Mn⁴⁺. The phosphor CsPF₆:Mn⁴⁺ prepared with the HPF₆/K₂MnF₆ molar ratio of 10 : 1 has the strongest red emission and the highest external quantum efficiency of 50.4% among the samples. It has high thermal quenching resistance and its emission intensity at 160 °C is about 1.1 times higher than that at room temperature. This sample also can remarkably improve the color rendering index and decrease the colour rendering index of white light-emitting diodes (w-LEDs). Hence, CsPF₆:Mn⁴⁺ could be used as a red-emitting phosphor for warm w-LEDs.