Phase homogeneity analysis of La0.99Sr0.01Nb0.99Al0.01O4−δ and La0.99Ca0.01Nb0.99Ti0.01O4−δ proton conductors by high-resolution STEM and EELS. Issue 5 (May 2015)

• Record Type: Journal Article
• Authors: Palisaitis, Justinas; Ivanova, Mariya E.; Meulenberg, Wilhelm A.; Guillon, Olivier; Mayer, Joachim
• Is Part Of: Journal of the European Ceramic Society. Volume 35:Issue 5(2015:May)
• Page Start: 1517
• Page End: 1525
• Publication Date: 2015-05
• Subjects: Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2014.11.010
• Languages: English
• ISSNs: 0955-2219

Abstract

<abstract abstract-type="author" id="abs0005"> <title id="sect0005">Abstract</title> <sec> <p id="spar0005">The microstructural and compositional homogeneity of La<sub>0.99</sub>Ca<sub>0.01</sub>Nb<sub>0.99</sub>Ti<sub>0.01</sub>O<sub>4−<italic>δ</italic></sub> and La<sub>0.99</sub>Sr<sub>0.01</sub>Nb<sub>0.99</sub>Al<sub>0.01</sub>O<sub>4−<italic>δ</italic></sub> proton conductors was studied using the combination of atomic-resolution scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and STEM image simulations. The obtained results revealed that gently doped proton conductors were predominantly composed of grains with a monoclinic lanthanum niobate crystal structure. In addition to the host phase, dopant-rich phases were also observed and identified. The La<sub>0.99</sub>Sr<sub>0.01</sub>Nb<sub>0.99</sub>Al<sub>0.01</sub>O<sub>4−<italic>δ</italic></sub> matrix accommodated dopant-rich grains retaining an LaAlO<sub>3</sub> cubic crystal structure with a significant fraction of Sr incorporated into them. The secondary phases embedded in the La<sub>0.99</sub>Ca<sub>0.01</sub>Nb<sub>0.99</sub>Ti<sub>0.01</sub>O<sub>4−<italic>δ</italic></sub> matrix possessed the pyrochlore La<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> crystal structure with Ca partially substituting La. High spatial resolution EELS revealed preferential Ca sites within the pyrochlore La<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> crystal lattice. The origin of the secondary phase formation and the role of these phases for the transport properties of co-doped lanthanum niobates are discussed here.</p> </sec> </abstract>