Novel Mn 4+ -Activated K 2 Nb 1- x Mo x F 7 (0 ≤ x ≤ 0.15) Solid Solution Red Phosphors with Superior Moisture Resistance and Good Thermal Stability.

Nowadays, Mn4+ -activated fluoride red phosphors with excellent luminescence properties have triggered tremendous attentions for enhancing the performance of white light-emitting diodes (WLEDs). Nonetheless, the poor moisture resistance of these phosphors impedes their commercialization. Herein, we proposed the dual strategies of "solid solution design" and "charge compensation" to design K2 Nb1- x Mo x F7 novel fluoride solid solution system, and synthesized the Mn4+ -activated K2 Nb1- x Mo x F7 (0 ≤ x ≤ 0.15, x represents the mol % of Mo6+ in the initial solution) red phosphors via co-precipitation method. The doping of Mo6+ not only significantly improve the moisture resistance of the K2 NbF7 : Mn4+ phosphor without any passivation and surface coating, but also effectively enhance the luminescence properties and thermal stability. In particular, the obtained K2 Nb1- x Mo x F7 : Mn4+ ( x = 0.05) phosphor possesses the quantum yield of 47.22% and retains 69.95% of its initial emission intensity at 353 K. Notably, the normalized intensity of the red emission peak (627 nm) for the K2 Nb1- x Mo x F7 : Mn4+ ( x = 0.05) phosphor is 86.37% of its initial intensity after immersion for 1440 min, prominently higher than that of the K2 NbF7 : Mn4+ phosphor. Moreover, a high-performance WLED with high CRI of 88 and low CCT of 3979 K is fabricated by combining blue chip (InGaN), yellow phosphor (Y3 Al5 O12 : Ce3+ ) and the K2 Nb1- x Mo x F7 : Mn4+ ( x = 0.05) red phosphor. Our findings convincingly demonstrate that the K2 Nb1- x Mo x F7 : Mn4+ phosphors have a good practical application in WLEDs.