Rubidium sesquioxide is a chemical compound with the formula Rb2O3 or more accurately Rb4O6. In terms of oxidation states, Rubidium in this compound has a nominal charge of +1, and the oxygen is a mixed peroxide (O2−2) and superoxide (O−2) for a structural formula of (Rb)4(O−2)2(O2−2). It has been studied theoretically as an example of a strongly correlated material.
The compound was predicted to be a rare example of a ferromagnetic compound that is magnetic due to a p-block element, and a half-metal that was conducting in the minority spin band. However, while the material does have exotic magnetic behavior, experimental results instead showed an electrically insulating magnetically frustrated system. Rb4O6 also displays a Verwey transition where charge ordering appears at 290 K.