Electrical conductivity of samarium–ytterbium zirconate ceramics

Abstract: (Sm1− x Yb x )2Zr2O7 (0≤ x ≤1.0) ceramic powders were prepared by chemical-coprecipitation and calcination method, and were pressureless-sintered at 1973K for 10h to fabricate dense bulk materials. (Sm1− x Yb x )2Zr2O7 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− x Yb x )2Zr2O7 was investigated by complex impedance spectroscopy over a frequency range of 200Hz to 20MHz from 723 to 1173K in air. The measured electrical conductivity obeys the Arrhenius relation. The grain conductivity of (Sm1− x Yb x )2Zr2O7 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 (Sm1− x Yb x )2Zr2O7 system, whereas activation energies for the conduction process increase monotonically as the structure becomes disordered. [Copyright &y& Elsevier]