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

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.