Synthesis and electrophysical properties of (1 − x)Ce0.8Gd0.2O2 − δ + xTiO2 (x = 0-0.06) solid-state solutions

In the present work the electrical properties of (1 − x)Ce0.8Gd0.2O2 − δ + xTiO2 (x = 0-0.06) synthesized by the standard ceramic technology were investigated, in a wide range of oxygen partial pressures (0.21-10− 20atm at 900 °C) and temperatures (600-900 °C), both in air and H2 + 3%H2O atmosphere. It was found, that only the introduction of above 1 mol% TiO2 decreases the sintering temperature of Ce0.8Gd0.2O2 − δ. The values of total electrical conductivity do not change significantly with the content of the sintering aid up to 3 mol%, while the activation energy of total conductivity in air decreases considerably with the introduction of TiO2 into Ce0.8Gd0.2O2 − δ from 87 to 67 kJ/mol; however, it is independent of x up to 0.03. The dependence of the total conductivity on the oxygen partial pressure is characterized by three regions. In the intermediate region (10− 10-10− 14) the conductivity behavior is described according to the oxygen vacancy model. The n-type conductivity region curve of Ce0.8Gd0.2O2 − δ is fitted to a -1/5 slope. The increase of TiO2 content leads to the slope increase at − 1/6, − 1/8 and − 1/9 for 1, 2 and 3 mol% TiO2, respectively, due to the trapping of electrons by Ti4+. 1 mol% doping increases the electrolytic region of Ce0.8Gd0.2O2 − δ from 10− 10 to 10− 13atm. Finally, the optimal content of TiO2 from the viewpoint of sintering and electrical properties was found to be 2 mol%.