Surface passivation to improve the water resistance and fluorescent thermal stability of K2SiF6:Mn4+ by using Na2S2O4 as a passivator

Mn 4+ doped fluoride emitting red phosphors are an important component for commercial white light emitting devices (WLEDs), but the poor moisture resistance and fluorescent thermal stability are the main obstacles for such phosphors in practical applications. In this study, a strategy for passivating K 2 SiF 6 :Mn 4+ (KSF:Mn 4+ ) phosphor with Na 2 S 2 O 4 is proposed. After passivation, a protective layer is formed on the surface of the phosphor, which significantly enhances the water resistance and fluorescent thermal stability of the optimal sample. The passivated sample can maintain 86.1% of the initial intensity when immersed in water for 6 h, and the fluorescence intensity at 180 °C is 4.11 times of the initial one at 30 °C. The LED package emits a warm white light with good performances. These results show that it has important potential applications in the field of WLED backlighting and displays. • Passivated sample P 2 –K 2 SiF 6 :Mn 4+ was synthesized. • Sample exhibits a good water resistance induced by surface passivation. • Emission intensity is improved by surface passivation. • Negative thermal quenching effect is enhanced by surface passivation.