Yttrium oxide, also known as yttria, is Y2O3. It is an air-stable, white solid substance.
Y 0641 (OTTO) Yttrium oxide, 99.9999% - used to make phosphors for color TV tubes, yttrium iron garnets for use as microwave filters, high temperature superconductors, as a mineralizing agent for the formation of spinel and as a stabilizer for high-temperature service materials.