Uranium oxide

Uranium oxide is an oxide of the element uranium.

Yellowcake, a mixture of uranium oxides.

The metal uranium forms several oxides:

• Uranium dioxide or uranium(IV) oxide (UO₂, the mineral uraninite or pitchblende)
• Diuranium pentoxide or uranium(V) oxide (U₂O₅)
• Uranium trioxide or uranium(VI) oxide (UO₃)
• Triuranium octoxide (U₃O₈), the most stable uranium oxide; yellowcake typically contains 70 to 90 percent triuranium octoxide)
• Uranyl peroxide (UO₂O₂ or UO₄)
• Amorphous uranium(VI) oxide (Am-U₂O₇)

Uranium dioxide is oxidized in contact with oxygen to form triuranium octoxide.

3 UO₂ + O₂ → U₃O₈ at 250 °C (523 K)

Preparation 38

During World War II, "Preparation 38" was the codename for uranium oxide used by German scientists.^[1][2][3]