Towards improved waterproofness of Mn⁴⁺-activated fluoride phosphors

Abstract

The Mn 4+ -activated fluoride phosphor, typically K 2 SiF 6 :Mn 4+ , has become a renowned red-emitting phosphor for white light emitting diodes (LEDs) due to its sharp...

Exploring dual-emission properties in Mn4+ distinctively activated BaTaF7 red emitting phosphor

“…Mn 4+ -activated fluoride phosphors have been extensively studied as red-emitting luminescent materials for white LEDs. [1][2][3][4] These fluoride phosphors, including A 2 XF 6 :Mn 4+ (A = Li, Na, K, Rb, and Cs; A 2 = Ba, Zn; X = Si, Ge, Sn, Ti, Zr, and Hf), A 3 MF 6 :Mn 4+ (M = Al, Ga, Sc, In), A 2 NF 7 :Mn 4+ (N = Nb, Ta), AZnF 3 :Mn 4+ , AHF 2 :Mn 4+ , and A 2 ZO 2 F 4 :Mn 4+ (Z = Mo, W), [5][6][7][8][9][10][11][12] have gained attention due to their broadband absorption in the blue region at B450 nm and sharp red-line emission at B630 nm. In recent years, extensive research has been conducted on Mn 4+ -doped fluoride materials due to their potential applications as red-emitting luminescent materials for white LEDs.…”

Crystal field optimization and fluorescence enhancement of a Mn4+-doped fluoride red phosphor with excellent stability induced by double-site metal ion replacement for warm WLED

“…Furthermore, due to the uneven distribution of the shell structure on the surface of the phosphor, the exposed [MnF 6 ] 2− groups are still hydrolyzed. 32,33 Stabilizing the presence of the Mn 4+ ion by adjusting the crystal field environment of the host is also considered as a feasible method to improve the fluorescence intensity and stability of the phosphors. For example, Zhong et al 34 and Li et al 35 successfully optimized the water stability and fluorescence intensity of Na 2 SiF 6 :Mn 4+ and BaSiF 6 :Mn 4+ phosphors by introducing Li + ion and Ge 4+ ion, respectively.…”

Highly Moisture-Stable and Enhanced Luminescence-Efficient Mn4+-Activated Red-Emitting Fluoride Phosphors via a Bi-hydrogen-Bond Organic Coating

“…Various strategies have been reported to improve the moisture resistance of Mn 4+activated fluoride phosphors and can be roughly classified into organic coating, inorganic heterogeneous/homogeneous coating, surface deactivation and cation substitution, etc. 13,15,16 Various inorganic compounds, such as TiO 2 , 17 Al 2 O 3 , 17,18 CaF 2 , 19,20 and SrF 2 21 have been used to form a heterogeneous protective layer to improve moisture resistance for fluoride phosphors but at the expense of sacrificing the luminescence efficiency generally due to surface defects and nonradiative decay probability induced by the differences of physicochemical properties between inner phosphors and the coating layer. 14 Moreover, an inorganic coating generally needs a gas-phase deposition technique or highly toxic HF as solvent to form an inorganic layer on the surface of phosphors, and synthesis processes are complex, polluting, and unsafe.…”

“…These advantages make Mn 4+ -activated fluoride phosphors very promising red-emitting phosphors for illumination and display fields . Nevertheless, poor moisture-resistant properties of Mn 4+ -activated fluoride phosphors hindered their practical application . This is because the surface [MnF 6 ] 2– group would be easily hydrolyzed into mixed-valence Mn oxides and hydroxides in a moisture environment, which darken the phosphor body color and weaken the red emission intensity.…”