Synthesis and electrophysical properties of (1 − x)Ce 0.8Gd 0.2O 2 − δ + xTiO 2 ( x = 0–0.06) solid-state solutions

Abstract

In the present work the electrical properties of (1 − x)Ce 0.8Gd 0.2O 2 − δ + xTiO 2 ( x = 0–0.06) synthesized by the standard ceramic technology were investigated, in a wide range of oxygen partial pressures (0.21–10 − 20 atm at 900 °C) and temperatures (600–900 °C), both in air and H 2 + 3%H 2O atmosphere. It was found, that only the introduction of above 1 mol% TiO 2 decreases the sintering temperature of Ce 0.8Gd 0.2O 2 − 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 TiO 2 into Ce 0.8Gd 0.2O 2 − 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 Ce 0.8Gd 0.2O 2 − δ is fitted to a -1/5 slope. The increase of TiO 2 content leads to the slope increase at − 1/6, − 1/8 and − 1/9 for 1, 2 and 3 mol% TiO 2, respectively, due to the trapping of electrons by Ti 4+. 1 mol% doping increases the electrolytic region of Ce 0.8Gd 0.2O 2 − δ from 10 − 10 to 10 − 13 atm. Finally, the optimal content of TiO 2 from the viewpoint of sintering and electrical properties was found to be 2 mol%.