Effect of Oxide Additions on the Polymorphism of Tantalum Pentoxide: II. "Stabilization" of the High Temperature...

The high temperature, apparently tetragonal, polymorph of tantalum pentoxide can be obtained at room temperature by quenching a specimen containing 2-5 mole percent of the following oxides:SnO₂, Ga₂O₃, Cr₂O₃, Fe₂O₃, Sc₂O₃, or MgO. All the x-ray patterns can be indexed on a body centered tetragonal cell with a ≈ 3.830 Å, c ≈ 35.68 Å. However, P₂O₅, V₂O₅, Nb₂O₅, ZrO₂, Lu₂O₃, NiO, or ZnO do not stabilize the tetragonal form at room temperature. Single crystals of scandium "stabilized" Ta₂O₅ have been grown by the Czochralski technique.