Preparation, Structural Characterization, and Enhanced Electrical Conductivity of Pyrochlore-type (Sm1-xEux)2Zr2O7 Ceramics

(Sm1xEux)2Zr2O7 (0?=?x?=?1.0) samples are prepared by solid state reaction method using Sm2O3, Eu2O3, and ZrO2 as starting materials. The phase composition and microstructure of (Sm1xEux)2Zr2O7 ceramics are investigated by X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction and Raman spectroscopy. XRD and TEM show that all the samples exhibit a single pyrochlore-type structure. HRTEM observation indicates that the whole grain interior of Sm2Zr2O7 ceramic is a perfect crystal free of any dislocation. Raman spectroscopy reveals that the degree of structural disorder of (Sm1xEux)2Zr2O7 ceramics increases gradually with increasing Eu content. The electrical conductivity of (Sm1xEux)2Zr2O7 ceramics is investigated by impedance spectroscopy in the air and hydrogen atmospheres, respectively. The electrical conductivity of (Sm1xEux)2Zr2O7 ceramics increases with increasing Eu content at identical temperature levels. Both the activation energy Eg and the pre-exponential factor s0g for the grain conductivity gradually increase with increasing Eu content. As the ionic conductivity shows no obvious change in both air and hydrogen atmospheres, the conduction of (Sm1xEux)2Zr2O7 is purely ionic with negligible electronic conduction.