Cerium oxide is an inorganic substance with the chemical formula CeO2, a light yellow or yellow brown powder. Density 7.13g/cm3, melting point 2397 ℃, insoluble in water and alkali, slightly soluble in acid. At a temperature of 2000 ℃ and a pressure of 15 MPa, cerium oxide can be reduced by hydrogen to obtain cerium trioxide. When the temperature is free between 2000 ℃ and the pressure is free at 5 MPa, cerium oxide appears slightly yellow with red color and pink color. Its properties include polishing materials, catalysts, catalyst carriers (additives), UV absorbers, fuel cell electrolytes, automotive exhaust absorbers, electronic ceramics, etc.