Methods for Evaluating Hydrolytic Degradation of Mn<sup>4+</sup>-activated Fluoride Phosphors

Abstract Hydrolytic degradation is one of the main obstacles limiting the widespread application of Mn 4+ -activated fluoride red phosphors.Accurate characterization of the hydrolytic degradation behavior of Mn 4+ -activated fluoride phosphors is crucial for a deeper understanding of their degradation mechanisms and for developing fluoride phos phors with superior hydrolytic resistance.This review summarizes the methods for evaluating the hydrolytic degra dation of Mn 4+ -activated fluoride phosphors which are categorized into characterization of luminescence intensity/ quantum efficiency (testing the luminescence intensity and quantum efficiency before and after treatment such as immersing in water treating under 85 /85% relative humidity condition treating in boiling water or treating in hydrothermal condition) characterization of Mn valance on the particle surface (diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy) and characterization of the dissolution properties of the phosphor (pH testing and conductivity testing of the solution after hydrolysis).By presenting specific examples this review intro duces the characteristics of various evaluation methods analyzes their advantages and disadvantages of each method and finally provides a perspective on how to scientifically evaluate the hydrolytic degradation behavior of fluoride phosphors.