Preparation, characterization and electrical conductivity studies of NdYb1−xGdxZr2O7 (0 ≤ x ≤ 1.0) ceramics

Several compositions of NdYb1−xGdxZr2O7 (0 ≤ x ≤ 1.0) ceramics were prepared by pressureless-sintering method at 1973 K for 10 h in air. The relative density, microstructure and electrical conductivity of NdYb1−xGdxZr2O7 ceramics were analyzed by the Archimedes method, X-ray diffraction, scanning electron microscopy and impedance plots measurements. NdYb1−xGdxZr2O7 (0 ≤ x ≤ 0.3) ceramics have a single phase of defect fluorite-type structure, and NdYb1−xGdxZr2O7 (0.7 ≤ x ≤ 1.0) ceramics exhibit a single phase of pyrochlore-type structure; however, the NdYb0.5Gd0.5Zr2O7 composition shows mixed phases of both defect fluorite-type and pyrochlore-type structures. The measured values of the grain conductivity obey the Arrhenius relation. The grain conductivity of each composition in NdYb1−xGdxZr2O7 ceramics gradually increases with increasing temperature from 673 to 1173 K. NdYb1−xGdxZr2O7 ceramics are oxide-ion conductor in the oxygen partial pressure range of 1.0 × 10−4 to 1.0 atm at all test temperature levels. The highest grain conductivity value obtained in this work is 1.79 × 10−2 S cm−1 at 1173 K for NdYb0.3Gd0.7Zr2O7 composition.