Promethium(III) oxide

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Promethium(III) oxide
Pm oxide.jpg
Powdered promethium oxide in a metal tray
Kristallstruktur Lanthanoid-C-Typ.png
Cubic form
Hexagonal form
CAS number 12036-25-8 YesY
Molecular formula Pm2O3
Molar mass 337.824 g/mol
Melting point ~2320 °C[1]
Crystal structure Cubic
Related compounds
Other anions Promethium(III) chloride
Other cations Neodymium(III) oxide, Samarium(III) oxide, Neptunium(III) oxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Promethium(III) oxide is a compound with the formula Pm2O3. It is the most common form of promethium.

Crystal structure[edit]

Promethium oxide exists in three major crystalline forms:[1]

Form Pearson symbol Space group No. a,b,c (nm) β(deg) Z Density
Cubic cI80 Ia3 206 1.099 16 6.85
Monoclinic mS30 C2/m 12 1.422; 0.365; 0.891 100.1 6 7.48
Hexagonal hP5 P3m1 164 0.3802; 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.


  1. ^ a b Chikalla, T. D.; McNeilly, C. E.; Roberts, F. P. (1972). "Polymorphic Modifications of Pm2O3". Journal of the American Ceramic Society 55 (8): 428. doi:10.1111/j.1151-2916.1972.tb11329.x.