Used as a key component in red phosphors for cathode ray tubes and LED displays, enabling bright red and white light emission. Employed in solid oxide fuel cells as a stabilizer for zirconia electrolytes, enhancing ionic conductivity at high temperatures. Serves as a host material for rare-earth-doped lasers and optical coatings due to its high thermal stability and transparency in the visible and near-infrared range. Applied in ceramics and glass manufacturing to improve strength, thermal shock resistance, and corrosion resistance. Utilized in biomedical applications such as radiographic contrast agents and in cancer treatment through yttrium-90 labeled compounds for targeted radiotherapy.