Used as a precursor in the synthesis of thulium-containing materials for specialized optical devices, lasers, and phosphors in light sources such as fluorescent lamps and displays. Employed in research settings to develop luminescent compounds that emit in the near-infrared range, useful for imaging, sensing, and optical communication applications. Serves as a dopant source in the production of solid-state lasers and amplifiers, particularly in fiber optics technology and medical devices. Also utilized in the preparation of catalysts for certain organic transformations, in advanced ceramics, and in the study of rare earth ion behavior in aqueous and solid matrices.