Used as a precursor in the synthesis of erbium-containing materials for optical applications, particularly in the production of upconversion phosphors and luminescent materials. Commonly employed in the fabrication of solid-state lasers and amplifiers, especially in the development of erbium-doped fiber amplifiers (EDFAs) used in telecommunications for signal boosting in fiber-optic networks. Also utilized in research settings for doping into glass or ceramic matrices to enhance infrared emission properties. Its hydrate form supports solubility in polar solvents, making it suitable for solution-based processing techniques like sol-gel and spin coating. Additionally, finds use in catalytic studies and in the preparation of erbium oxide films for electronic and photonic devices.