Physical-chemical investigations on Gd-, Eu- and In-doped BaCeO3 ceramics

The system BaCe1-xMxO3-alpha (Me = Gd, Eu, In) was prepared in a concentration range 0.05 less than or equal to x less than or equal to 0.25 mole and the physical-chemical properties ascertained. The doped barium cerates correspond with the structure of the BaCeO3 with a small amount of CeO2. The compounds are stable in reducing and oxidizing atmosphere and have a high solubility of oxygen. The doped BaCeO3 indicate a point defect behaviour in the oxygen partial pressure range from 1 bar to 10(-6) bar. The maximum of the total electrical conductivity was found at a content of 0.15 mole for GdO1.5, InO1.5 and 0.10 mol for EuO1.5. The electrical conductivity of Gd-, Eu-doped BaCeO3 exceeds the conductivity of Y17SZ*. The mean ionic transport number is t(ion) = 1 in hydrogen above 700 degrees C whereas in argon a deviation from 1 is observed. A small deviation from 1 is detected also for Eu- and In-doped BaCeO3 under hydrogen at 850 degrees C. Our investigations cover the temperature range between 700 degrees C and 1000 degrees C.