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Wikipedia / Promethium(III) oxide

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:

Form

Pearson symbol

Space group

No.

a; b; c (nm)

β(deg)

Z

Density (g/cm3)

Cubic

cI80

Ia

206

1.099

16

6.85

Monoclinic

mS30

C2/m

12

1.422; 0.365; 0.891

100.1

6

7.48

Hexagonal

hP5

Pm1

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.

References