Used as a precursor in the synthesis of erbium-doped materials for optical applications, particularly in the production of upconversion nanoparticles and luminescent compounds. These materials are essential in bioimaging, cancer therapy, and security inks due to their ability to emit visible light under near-infrared excitation. Also employed in the fabrication of specialty glasses and ceramics with enhanced optical properties for use in telecommunications and laser technologies. Its solubility in water and organic solvents makes it suitable for solution-based processing techniques like spin coating and sol-gel methods.