Europium(III) sulfate octahydrate serves as a high-purity source of Eu³⁺ ions for preparing red phosphors in cathode ray tubes and fluorescent lamps, enabling bright red emission when the derived materials are excited by electrons or ultraviolet light. It is employed in the synthesis of europium-based luminescent materials for display technologies and anti-counterfeiting inks, leveraging the sharp emission lines of europium. Acts as a key precursor for other europium-containing compounds used in optical devices and sensors. Widely utilized in research for doping solid-state materials to enhance luminescent properties.