Data were presented on the evolution of the pyrochlore structure in Ln2+xHf2−xO7−δ (Ln = Sm, Eu; x = 0.096) solid solutions and in Ln2Hf2O7 (Ln = Gd, Tb) compounds prepared from mechanically activated oxide mixtures. It was shown that Sm2.096Hf1.904O6.952 underwent pyrochlore to disordered pyrochlore to pyrochlore (P-P1-P) phase transformations at 1200 to 1670C. The former transformation led to an increase in the 840C conductivity from 10−4 to 3 x 10−3S/cm in samples synthesized at 1600C, and the latter led to a decrease in the 840C conductivity to 6 x 10−4S/cm in samples synthesized at 1670C. A reduction in the conductivity of Sm2.096Hf1.904O6.952 was accompanied by disappearance of the assumed superstructure. At 1300 to 1670C, Eu2+xHf2−xO7−δ (x = 0.096) and Ln2Hf2O7 (Ln = Gd, Tb) had a disordered pyrochlore structure. The highest 840C conductivities were exhibited by Sm2.096Hf1.904O6.952, Gd2Hf2O7 and Tb2Hf2O7 synthesized at 1670C: with 7.5 x 10−3, 5 x 10−3 and 2.5 x 10−2S/cm, respectively.

Structure and Electrical Conductivity of Ln2+xHf2−xO7−x/2 (Ln = Sm-Tb; x = 0, 0.096). A.V.Shlyakhtina, M.V.Boguslavskii, S.Y.Stefanovich, I.V.Kolbanev, A.V.Knotko, O.K.Karyagina, S.A.Borisov, L.G.Shcherbakova: Inorganic Materials, 2006, 42[5], 519-27