Rubidium sesquioxide is a chemical compound with the formula or more accurately . In terms of oxidation states, rubidium in this compound has a nominal charge of +1, and the oxygen is a mixed peroxide () and superoxide () for a structural formula of . It has been studied theoretically as an example of a strongly correlated material.
The compound crystallizes in a body-centered cubic form with the same crystal structure as and .
Rubidium sesquioxide can be prepared by reacting the peroxide and the superoxide :
It was initially discovered in 1907, and more thoroughly characterized in 1939.
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. also displays a Verwey transition where charge ordering appears at 290 K.