Promethium(III) oxide is a
compound
Compound may refer to:
Architecture and built environments
* Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall
** Compound (fortification), a version of the above fortified with defensive struct ...
with the formula Pm
2O
3. It is the most common form of
promethium
Promethium is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in Earth's crust at any given time. Promethium is one of onl ...
.
Crystal structure
Promethium oxide exists in three major crystalline forms:
*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.
References
Promethium compounds
Sesquioxides
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