Search results for " barium zirconate"

showing 3 items of 3 documents

Dopants and defects: local structure and dynamics in barium cerates and zirconates

2010

In this paper we present an overview of state-of-the-art EXAFS measurements and data analysis on Ba, Ce, Zr, Y, In and Gd local environments in Y:BaCeO3, In:BaCeO3, Gd:BaCeO3, Y:BaZrO3, and In:BaZrO3, at different temperatures, hydration degrees and doping levels. This approach allows to reach unprecedented insights on the peculiar role of the dopant, and its interactions with the other lattice defects. In particular, we evidence that each different dopant shows unique behavior, depending mainly on its electronic structure, and that the usual criterion of ionic radius matching is not useful to outline an effective doping strategy of proton-conducting perovskites. As what concerns the struct…

Materials scienceIonic radiusExtended X-ray absorption fine structureDopantInorganic chemistryDopingEXAFS perovskite proton conductorGeneral ChemistryElectronic structureConductivityCondensed Matter PhysicsChemical physicsGeneral Materials ScienceProton conductorPerovskite (structure)EXAFS perovskite proton conductor barium zirconate barium cerate
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Proton Dynamics in In:BaZrO3: Insights on the Atomic and Electronic Structure from X-ray Absorption Spectroscopy

2009

The local structure of Ba2+, Zr4+, and In3+ in In:BaZrO3 is investigated with EXAFS for samples having 0 to 75% In3+ content. It is found that indium can be inserted in any ratio in the host matrix oxide and that the oxygen coordination shell displays an In-O distance very similar to the Zr-O length. In the Zr-rich compositions, there is a preferred dopant-vacancy association that, however, does not give rise to dopant-proton interaction in the hydrated samples. The tendency of Ba2+ to be attracted toward the dopant site is attributed to the electrostatic interaction with the dopant and to the structural rearrangement around the In3+ site. Third cumulant analysis at high temperatures (up to…

X-ray absorption spectroscopyProtonExtended X-ray absorption fine structureChemistryGeneral Chemical EngineeringAnalytical chemistrychemistry.chemical_elementGeneral ChemistryElectronic structureLocal structureMatrix (chemical analysis)Materials ChemistryIndiumproton conductor perovskite EXAFS barium zirconate
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Y:BaZrO3 Perovskite Compounds I: DFT Study on the Unprotonated and Protonated Local Structures

2011

Y-doped BaZrO(3) derivatives were studied by density functional theory (DFT) to investigate the local arrangements of the octahedral sites in Pm3m cubic frameworks. Single- and double substitution of zirconium by yttrium were considered, including in the presence of a nearby oxygen vacancy. Although the structural symmetry of undoped barium zirconate was not modified after yttrium doping, the presence of yttrium induced several differences in the oxygen sites around it, according to the local geometrical arrangement of yttrium in the host matrix. As an example, the differences between such oxygen sites were shown in the presence of a proton. In this case, different stabilization energies ch…

ZirconiumProtonChemistryProtonic conductionOrganic ChemistryInorganic chemistrychemistry.chemical_elementProtonationyttrium-doped barium zirconateGeneral ChemistryYttriumSiestaBiochemistryDFTCondensed Matter::Materials ScienceCrystallographyOctahedronSettore CHIM/03 - Chimica Generale E InorganicaDensity functional theoryfuel-cellOrder of magnitudeperovskitePerovskite (structure)
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