Promethium(III) oxide is a compound with the formula Pm2O3. It is the most common form of promethium.
Crystal structure Promethium oxide exists in three major crystalline forms: FormPearson symbol Space group No.a; b; c (nm)β(deg)ZDensity (g/cm3)Cubic cI80 Ia2061.099 166.85MonoclinicmS30C2/m121.422; 0.365; 0.891100.167.48HexagonalhP5Pm11640.3802; 0.3802; 0.5954 1 7.62 *a, b and c are lattice parameters, Z is the number of formula units per unit cell, density is calculated from X-ray data.
The low-temperature cubic form converts to the monoclinic structure upon heating to 750–800 °C, and this transition can only be reversed by melting the oxide. The transition from the monoclinic to hexagonal form occurs at 1740 °C.
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