Dielectric behavior of Ce1-Gd O2-δ (0≤ x ≤0.1) ceramics prepared by sol-gel method

The Ce1-xGdxO2-δ (GDC) with 0, 0.0005, 0.001, 0.01, and 0.1 ceramics were prepared by sol-gel method. Dielectric properties of these samples were investigated in the temperature range of 300–1000 K and frequency range of 102–106 Hz. Our results revealed two thermally activated relaxations in all samples. The low-temperature relaxation (R1) with an activation energy of ∼0.70 eV has been widely reported in GDC ceramics. Instead of the usually mechanism of oxygen-vacancy-dopant defect pairs for R1, our results indicate that this relaxation is a Maxwell-Wagner relaxation resulting from surface layer effect caused by humidity sensitivity. The high-temperature relaxation (R2) is associated with oxygen vacancies, which exist in isolated state in the samples with the doping levels of x ≤ 0.01 and in clustered state in the sample with the doping level of x = 0.1.