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Isolating the two room-temperature polymorphs of NaNbO3 : structural features, optical band gap, and reactivity

hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorGOUGET, Guillaume
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorDUTTINE, Mathieu
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorDURAND, Etienne
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorVILLESUZANNE, Antoine
hal.structure.identifierInstitut des Sciences Moléculaires [ISM]
dc.contributor.authorRODRIGUEZ, Vincent
hal.structure.identifierInstitut des Sciences Moléculaires [ISM]
dc.contributor.authorADAMIETZ, Frédéric
hal.structure.identifierSolvay (France)
dc.contributor.authorLE MERCIER, Thierry
hal.structure.identifierSolvay (France)
dc.contributor.authorBRAIDA, Marc-David
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorDEMOURGUES, Alain
dc.date.issued2019
dc.identifier.issn2637-6113
dc.description.abstractEnThe two room-temperature NaNbO3 polymorphs crystallizing with orthorhombic symmetry have been successfully isolated at using a new preparative method. The pure polar phase, annealed at 600 °C under air after hydrothermal treatment at 200 °C, adopts the P21ma space group, whereas the well-known and thermodynamically stable form with the Pbma structure is obtained at higher temperatures under air (T = 950 °C). Thanks to the combination of powder XRD Rietveld analysis, 23Na solid-state NMR spectroscopy, and second harmonic generation studies, structural features of both these polymorphs reveal clear structural differences. The stability of each atom site is investigated by means of bond distances, Madelung potentials, and DFT calculations. The key role of Na atomic positions is highlighted, especially how they influence the [NbO6] octahedron distortion. In the polar P21ma phase, the higher distortion along both the apical axis and the equatorial plane is consecutive to the relaxation of the overall network with the stabilization of Na atoms in two sites sharing the same symmetry. Focusing on oxygen mobility, both polymorphs show distinct reactivities toward reductive heat treatments: as characterized by thermogravimetric analysis and ESR measurements, the Pbma framework is relatively insensitive, while the P21ma one yields a nonstoichiometric oxide with a Nb4+ content of 18% corresponding to NaNbO2.91 chemical composition. The fine control in phasic purity together with advances on the structural features of room-temperature phases should benefit both nonlinear optical applications and photocatalytic performances of sodium niobates.
dc.language.isoen
dc.publisherAmerican Chemical Society
dc.subject.enacentric structure
dc.subject.encompeting bonds
dc.subject.enhydrothermal synthesis
dc.subject.enperovskites
dc.subject.enreducibility
dc.subject.ensecond harmonic generation
dc.subject.ensodium niobates
dc.subject.enstructural distortions
dc.title.enIsolating the two room-temperature polymorphs of NaNbO3 : structural features, optical band gap, and reactivity
dc.typeArticle de revue
dc.identifier.doi10.1021/acsaelm.8b00125
dc.subject.halChimie/Matériaux
dc.subject.halChimie/Chimie inorganique
bordeaux.journalACS Applied Electronic Materials
bordeaux.page513-522
bordeaux.volume1
bordeaux.issue4
bordeaux.peerReviewedoui
hal.identifierhal-02121234
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-02121234v1
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