Effect of oxide additions on the polymorphism of tantalum pentoxide. II. ""Stabilization"" of the high temperature structure type

The hi gh temperature, ap paren tl y tetragonal, polymorph of ta ntalum pentoxide ca n be ob tai ned at room tempe rature by quen c hin g a specim en co ntainin g 2-5 mole perce nt of the follow in g oxides: S n0 2' Ga,O", C r,O ", Fe 20 ", Sc20", or MgO. All the xray pattern s ca n be ind exed on a body ce ntered tetrago nal cell with a = 3.830 A, C = 35.68 A However, P ,O " V 20 5 , N b20 " ZrO " LU 20 3, NiO , or ZnO do not stabilize the tetragonal form at room te mperature. Sin gle crystals of scand ium "stab ilized " Ta20 , have bee n grow n by th e Czochra ls ki tec hnique.