Thermal and electrical properties of rare-earth co-doped ceria ceramics

Sol–gel method was used to prepare rare-earth co-doped ceria ceramics with composition of Ce0.8Gd0.2−xYxO2 (0 ≤ x ≤ 0.1). The phase identification, morphology, thermal expansion and electrical properties of samples were studied by XRD, SEM, Dilatometry and Impedance spectroscopy. All compounds have the cubic structure (Fm3¯m space group). The lattice parameters were determined by X-ray powder diffraction. The thermal expansion is linear for all the samples. The thermal expansion coefficient (TEC), determined in the temperature range from room temperature to 1000 °C, increases with x. The results showed that Ce0.8Gd0.15Y0.05O2 and Ce0.8Gd0.1Y0.1O2 posses higher conductivity and lower activation energy than pure gadolinium-doped ceria (GDC). Impedance measurements indicate the presence of unassociated defect which relax with an activation energy in the range 1–1.2 eV. The Cole–Cole plots show semicircles in the temperature range 250–350 °C.