The Praseodymium-oxygen system is a system of oxides of praseodymium at different phases.
| Value | Formula | Phase | x in PrOx | Average oxidation state of Pr |
|---|---|---|---|---|
| 4 | Pr2O3 | θ | 1.5 | 3 |
| 7 | Pr7O12 | ι | 1.714 | 3.428 |
| 9 | Pr9O16 | ζ | 1.778 | 3.556 |
| 10 | Pr5O9 | ε | 1.8 | 3.6 |
| 11 | Pr11O20 | δ | 1.818 | 3.636 |
| 12 | Pr6O11 | β | 1.833 | 3.667 |
| ∞ | PrO2 | 2 | 4 |
This occurs due to the oxides being composed of octahedral Frenkel defects {Pr3+
2Pr4+
1.5O6}.Cite error: A <ref> tag is missing the closing </ref> (see the help page).