Mn-Activated Fluoride Phosphors Modified by Surfactant with Outstanding Water Resistance and Luminescent Thermal Properties

Abstract

Although Mn4+-activated fluoride phosphors have high luminescence quality, their poor water resistance and thermal fluorescence properties significantly limit their practical applications. Here, we propose a surfactant modification strategy by adding the surfactant cetyltrimethylammonium bromide (CTAB) to the synthesis and modifying the surface of the phosphor with ethylene diamine tetraacetic acid (EDTA) to obtain a phosphor with excellent luminescence thermal properties and water resistance, K2TiF6:Mn4+-xCTAB-EDTA (KTFM-xC-E) phosphors. The experimental and X-ray diffraction Rietveld refinement results confirm that the phosphor has higher structural rigidity and thus improved thermal stability. The surface modification with EDTA resulted in the formation of a dilute Mn4+ shell layer on the phosphor surface, which prevented the inward hydrolysis of the phosphor and resulted in excellent water resistance. Therefore, we have successfully modified K2TiF6:Mn4+ (KTFM) phosphors using low-cost surfactants, which also provides new ideas for other commercial high-quality phosphors.

Millimeter-Sized K2MnF6:Si4+, NH4+ Red-Luminescent Crystals with High Absorption Efficiency (AEmax of 93.5%) and External Quantum Efficiency (EQEmax of 68.9%) Grown by Cooling-Induced Crystallization

“…Red-luminescent Mn 4+ -activated fluoride phosphors, typically K 2 SiF 6 :Mn 4+ , have been commercially used in white light-emitting diodes (WLEDs) backlights for liquid crystal displays to achieve a wide color gamut . However, the fluoride phosphors exhibit poor moisture resistance as the [MnF 6 ] 2– groups, especially those at the particle surface and grain boundary, are prone to undergo hydrolysis. , This would lead to the formation of Mn-(hydro)­oxides, causing a severe decrease of the luminescence efficiency. One way is to develop oxide-based red phosphors − with high stability such as Sr 3 TaO 5.5 :Eu 2+ ; alternatively, a series of strategies have been utilized for the fluoride phosphors to improve the waterproofness.…”