Journal
IONICS
Volume 26, Issue 9, Pages 4621-4633Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s11581-020-03614-5
Keywords
Pyrochlores; O conductors; Diffusion; Isotope exchange of oxygen; Modeling; 2D diffusion
Funding
- Boreskov Institute of Catalysis [AAAA-A17-117041110045-9]
- state task for FRCCP [AAAA-A20-120013190076-0]
- Russian Science Foundation [16-13-00112]
- Russian Science Foundation [19-13-11004] Funding Source: Russian Science Foundation
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Oxides with pyrochlore structure are promising materials for SOFCs, oxygen and hydrogen separation membranes, and other devices. Ln zirconates attract interest due to their oxygen and protonic mobility. In this work, oxygen transport mechanism in Mg-doped Sm and Gd zirconates was studied. Sm1.9Mg0.1Zr2O6.95 and Gd1.9Mg0.1Zr2O6.95 oxides have been prepared via the mechanical activation and characterized by XRD, TGA, and SEM. Oxygen transport features were studied by the oxygen isotope exchange with (CO2)-O-18. Isotope substitution of bulk oxygen was demonstrated to be described by the 2D diffusion model. Very fast diffusion within grain boundaries provides fast isotope label distribution over the oxide domains, then tracer distributes due to a slower diffusion within domains' bulk. Three forms of oxygen were distinguished within grains' bulk. Very fast diffusion along grain boundaries (D-gb similar to 10(-7) cm(2)/s at 700 degrees C) can provide high rates of oxygen transport in oxygen separation membranes.
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