Abstract
(Sm 1 − x Yb x ) 2Zr 2O 7 (0 ≤ x ≤ 1.0) ceramic powders were prepared by chemical-coprecipitation and calcination method, and were pressureless-sintered at 1973 K for 10 h to fabricate dense bulk materials. (Sm 1 − x Yb x ) 2Zr 2O 7 has a single phase with a pyrochlore or defect fluorite structure, depending mainly upon the Yb content. They are found to be pyrochlores for 0 ≤ x ≤ 0.1, and defect fluorites for 0.3 ≤ x ≤ 1.0. The electrical conductivity of (Sm 1 − x Yb x ) 2Zr 2O 7 was investigated by complex impedance spectroscopy over a frequency range of 200 Hz to 20 MHz from 723 to 1173 K in air. The measured electrical conductivity obeys the Arrhenius relation. The grain conductivity of (Sm 1 − x Yb x ) 2Zr 2O 7 ceramics gradually increases with increasing temperature. A decrease of about one order of magnitude in grain conductivity is found at all temperature levels when the Yb content increases from x = 0.1 to x = 0.3. The electrical conductivities of defect fluorite-type materials are lower than those of pyrochlore-type materials in (Sm 1 − x Yb x ) 2Zr 2O 7 system, whereas activation energies for the conduction process increase monotonically as the structure becomes disordered.
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