Samarium(III) Oxide is a chemical compound with the chemical formula Sm2O3. It is a highly insoluble thermally stable Samarium source suitable for glass, optic and ceramic applications. Samarium oxide readily forms on the surface of samarium metal under humid conditions or temperatures in excess of 150°C in dry air. The oxide is commonly white to off yellow in color and is often encountered as a highly fine dust like pale yellow powder, which is insoluble in water.