期刊
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
卷 35, 期 4, 页码 1239-1253出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.jeurceramsoc.2014.11.009
关键词
Proton-conducting ceramic materials; Hydrogen transport ceramic membranes; Rare earth ortho-niobates; Acceptor-doped lanthanum niobates
资金
- Helmholtz Association, Initiative and Networking Fund, MEM-BRAIN Portfolio
Lanthanum niobates with general formulas of La0.99X0.01Nb0.99Al0.01O4-delta and La0.99X0.01Nb0.99Ti0.01O4-delta (X = Mg, Ca, Sr or Ba) were synthesized via the conventional solid state reaction. Specimens with relative density above 96% were produced after sintering. Structural and phase composition studies revealed predominant monoclinic Fergusonite structure for the majority of samples. SEM and TEM studies elucidated the effect of the used dopant combinations on grain growth, micro-crack formation and secondary phase formation. Results from microstructural study were correlated to the grain interior and grain boundary conductivities for selected samples (La0.99Sr0.01Nb0.99Al0.01O4-delta and La0.99Sr0.01Nb0.99Ti0.01O4-delta). The majority of co-doped niobates exhibited appreciable protonic conductivity under humid atmospheres at intermediate temperatures. Sr- or Ca-doped compounds displayed the highest total conductivities with values for LSNA equal to 6 x 10-(4) S/cm and 3 x 10(-4) S/cm in wet air and in wet 4% H-2-Ar (900 degrees C), respectively. Additionally, thermal expansion was studied to complete functional characterization of co-doped LaNbO4. (C) 2014 Elsevier Ltd. All rights reserved.
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