Structure and electrical conductivity of Ln2+x
Hf2?x
O7?x/2 (Ln = Sm-Tb; x = 0, 0.096) |
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| Authors: | A V Shlyakhtina M V Boguslavskii S Yu Stefanovich I V Kolbanev A V Knotko O K Karyagina S A Borisov L G Shcherbakova |
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| Affiliation: | (1) Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 119991, Russia;(2) Moscow State University, Vorob’evy gory 1, Moscow, 119899, Russia;(3) Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 119991, Russia;(4) Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125047, Russia |
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| Abstract: | Data are presented on the evolution of the pyrochlore structure in the Ln2+x Hf2?x O7?δ (Ln = Sm, Eu; x = 0.096) solid solutions and Ln2Hf2O7 (Ln = Gd, Tb) compounds prepared from mechanically activated oxide mixtures. Sm2.096Hf1.904O6.952 is shown to undergo pyrochlore-disordered pyrochlore-pyrochlore (P-P1-P) phase transformations in the temperature range 1200–1670°C. The former transformation leads to a rise in 840°C conductivity from 10?4 to 3 × 10?3 S/cm in the samples synthesized at 1600°C, and the latter leads to a drop in 840°C conductivity to 6 × 10?4 S/cm in the samples synthesized at 1670°C. The reduction in the conductivity of Sm2.096Hf1.904O6.952 is accompanied by the disappearance of the assumed superstructure. In the range 1300–1670°C, Eu2+x Hf2?x O7?δ (x = 0.096) and Ln2Hf2O7 (Ln = Gd, Tb) have a disordered pyrochlore structure. The highest 840°C conductivity is offered by Eu2.096Hf1.904O6.952, Gd2Hf2O7, and Tb2Hf2O7 synthesized at 1670°C: 7.5 × 10?3, 5 × 10?3, and 2.5 × 10?2 S/cm, respectively. |
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