|Appearance||pale yellow crystalline solid|
| 500 °C (932 °F; 773 K) (decomposes)|
|Fm3m (No 225)|
a = 0.5637 nm
Except where otherwise noted, data are given for materials in their
Polonium dioxide (also known as polonium(IV) oxide) is a chemical compound with the formula
At room temperature, polonium dioxide has a
is about 0.73, the lower limit of stability for the cubic crystal system, allowing polonium dioxide to have two modifications. When freshly prepared, polonium dioxide is always in the tetragonal form, and changes to the cubic form after being left to stand or after being cooled strongly.