SYNTHESIS, STRUCTURE AND ELECTROCHEMICAL PROPERTIES OF IN-DOPED BACEO3

Samples in the system BaCe1-xInxO3-alpha were prepared in a concentrat ion range 0.05 mole less than or equal to x less than or equal to 0.25 mole InO1.5 and the physical-chemical properties determined. The maxi mum doping level is 0.20 mole InO1.5 in BaCeO3 for which almost single phase products were obtained. The doped barium cerates correspond wit h the structure of BaCeO3 with a small amount of CeO2. The compounds a re stable in reducing and oxidizing atmospheres and have a high solubi lity of oxygen. The In-doped BaCeO3 shows a point defect behaviour in the oxygen pressure range from 1 bar to 10(-6) bar. The highest total electrical conductivity was observed for a content of 0.20 mole InO1.5 in BaCeO3. It is influenced by the water vapour partial pressure in r educing and inert gases in the temperature range from 700 degrees C to 1000 degrees C. The electrical conductivity of In-doped BaCeO3 does n ot exceed the conductivity of yttria-stabilized zirconia and not even that of the brownmillerite-structure oxides Ba2In2-xCexO5. The mean io nic transport number is (t) over bar(ion) = 1 in hydrogen between 630 degrees C and about 800 degrees C whereas above 800 degrees C a deviat ion from 1 is detected. In argon larger deviations from 1 are observed in the whole temperature range. (C) 1998 Elsevier Science B.V. All ri ghts reserved.