Protactinium(V) oxide

Protactinium(V) oxide is a chemical compound with the formula Pa₂O₅. When it is reduced with hydrogen, it forms PaO₂. Aristid V. Grosse was first to prepare 2 mg of Pa₂O₅ in 1927. Pa₂O₅ does not dissolve in concentrated HNO₃, but dissolves in HF and in a HF + H₂SO₄ mixture and reacts at high temperatures with solid oxides of alkali metala and alkaline earth metals.

As protactinium(V) oxide, like other protactinium compounds, is radioactive, toxic and very rare, it has very limited technological use. Mixed oxides of Nb, Mg, Ga and Mn, doped with 0.005–0.52% Pa₂O₅, have been used as high temperature dielectrics (up to 1300 °C) for ceramic capacitors.