Ytterbium(III) oxide is the chemical compound with the formula Yb<sub>2</sub>O<sub>3</sub>. It is one of the more commonly encountered compounds of ytterbium. It occurs naturally in trace amounts in the mineral gadolinite. It was first isolated from this in 1878 by Jean Charles Galissard de Marignac.
Ytterbium(III) oxide can be obtained by directly reacting ytterbium with oxygen:
It can also be obtained by the thermal decomposition of ytterbium carbonate or ytterbium oxalate at temperatures around 700 ðC:
Ytterbium(III) oxide is a white powder. It reacts with carbon tetrachloride or hot hydrochloric acid to form ytterbium(III) chloride:
Like the other trivalent oxides of the heavier lanthanides, ytterbium(III) oxide has the "rare-earth C-type sesquioxide" structure which is related to the fluorite structure with one quarter of the anions removed, leading to ytterbium atoms in two different six coordinate (non-octahedral) environments.