Electrical conductivity of samarium-ytterbium zirconate ceramics

(Sm1-xYbx)(2)Zr2O7 (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. (Sm1-xYbx)(2)Zr2O7 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 (Sm1-xYbx)(2)Zr2O7 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 (Sm1-xYbx)(2)Zr2O7 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 tox= 0.3. The electrical conductivities of defect fluorite-type materials are lower than those of pyrochlore-type materials in (Sm1-xYbx)(2)Zr2O7 system, whereas activation energies for the conduction process increase monotonically as the structure becomes disordered. (C) 2009 Elsevier Ltd. All rights reserved.