Silica-coating of Ca14Al10Zn6O35:Mn4+ particles and their luminescence properties

A simple method for improving water-resistance of Ca14Al10Zn6O35:Mn4+ (CZA) phosphor particles by silica-coating was developed in this work. Coating of the CZA particles having a particle size of ca. 3 µm with silica shells having a thickness of 158.3–194.4 nm was performed by adding tetraethyl orthosilicate/ethanol solution and ammonia solution or sodium hydroxide solution as base catalyst to ethanol dispersing the CZA particle powder (CZA/SiO2). The surfaces of the CZA/SiO2 particles were similar to the surface that appears to be derived from the surfaces of the silica particles prepared by the sol–gel method, i.e., were smoother than those of uncoated CZA particles, the element Si was present on the CZA/SiO2 particle surfaces, and the element Ca was present inside the CZA/SiO2 particles, which indicated that each CZA/SiO2 particle was composed of a CZA particle as its core and silica as its shell. Luminescence intensity of the CZA particles in water was not dominantly decreased with the silica-coating, which indicated that the silica-coating had a water-resistance capability.