Beyond the ionic radii: A multifaceted approach to understand differences between the structures of LnNbO4 and LnTaO4 fergusonites

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dc.contributor.authorMullens, BGen_AU
dc.contributor.authorSaura-Múzquiz, Men_AU
dc.contributor.authorMarlton, FPen_AU
dc.contributor.authorAvdeev, Men_AU
dc.contributor.authorBrand, HEAen_AU
dc.contributor.authorMondal, Sen_AU
dc.contributor.authorVaitheeswaran, Gen_AU
dc.contributor.authorKennedy, BJen_AU
dc.date.accessioned2024-08-22T01:58:11Zen_AU
dc.date.available2024-08-22T01:58:11Zen_AU
dc.date.issued2023-01-05en_AU
dc.date.statistics2024-08-22en_AU
dc.description.abstractSynchrotron X-ray powder diffraction methods have been used to obtain accurate structures of the lanthanoid tantalates, LnTaO4, at room temperature. Three different structures are observed, depending on the size of the Ln cation: P21/c (Ln = La, Pr), I2/a (Ln = Nd-Ho), and P2/c (Ln = Tb-Lu). BVS analysis indicated that TaV is six-coordinate in these structures, with four short bonds and two longer bonds. Synchrotron X-ray powder diffraction methods were also used to observe the impact of Ta doping on the orthoniobates, Ln(Nb1-xTax)O4 (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Lu). Where both the niobate and tantalate oxide were isostructural (fergusonite structure, space group I2/a), complete solid solutions were prepared. In these solid solutions, the unit cell volume decreases as the Ta content increases. The subtle interaction evident between the LnO8 and BO6 sublattices in the fergusonite-type oxides was not observed in the related pyrochlore oxides. A combined synchrotron X-ray and neutron powder diffraction study of the series Ho(Nb1-xTax)O4 was used to determine accurate atomic positions of the anions, and hence, bond lengths. This revealed a change in the (Nb/Ta)-O bond lengths, reflective of the difference in the valence orbitals of Nb(4d) and Ta(5d). Examination of the partial density of states demonstrates differences in the electronics between Nb and Ta, leading to a difference in the bandgap. This study highlights the importance of the long B-O contacts in the fergusonite structures, and its potential impact on the I2/a to I41/a phase transition. © 2022 Elsevier B.V.en_AU
dc.description.sponsorshipBJK acknowledges the support of the Australian Research Council for this work that was facilitated by access to Sydney Analytical, a core research facility at the University of Sydney. BGM acknowledges the Australian Institute for Nuclear Science and Engineering for a PGRA scholarship. Part of this work was undertaken at the powder diffraction beamline at the Australian Synchrotron. MSM acknowledges the financial support from the Comunidad de Madrid, Spain, through an “Atracción de Talento Investigador” fellowship (2020-T2/IND-20581). SM acknowledges DRDO, India, through ACRHEM (DRDO/18/1801/2016/01038: ACRHEM-PHASE-III). GV would like to acknowledge Institute of Eminence, University of Hyderabad (UoH-IoE-RC3-21-046) for funding and CMSD University of Hyderabad for providing the computational facility. SM thanks Ms. Anuroopa Behatha from IIT Hyderabad for technical help.en_AU
dc.identifier.articlenumber167399en_AU
dc.identifier.citationMullens, B. G., Saura-Múzquiz, M., Marlton, F. P., Avdeev, M., Brand, H. E. A., Mondal, S., Vaitheeswaran, G., & Kennedy, B. J. (2023). Beyond the ionic radii: A multifaceted approach to understand differences between the structures of LnNbO4 and LnTaO4 fergusonites. Journal of Alloys and Compounds, 930, 167399. doi:10.1016/j.jallcom.2022.167399en_AU
dc.identifier.issn0925-8388en_AU
dc.identifier.journaltitleJournal of Alloys and Compoundsen_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.jallcom.2022.167399en_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15656en_AU
dc.identifier.volume930en_AU
dc.languageEnglishen_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectAtomic radiien_AU
dc.subjectSynchrotronsen_AU
dc.subjectDiffractionen_AU
dc.subjectTantalatesen_AU
dc.subjectAmbient temperatureen_AU
dc.subjectLanthanumen_AU
dc.subjectNiobiumen_AU
dc.subjectTantalumen_AU
dc.subjectValenceen_AU
dc.subjectOrbitsen_AU
dc.subjectCrystal structureen_AU
dc.subjectIonic conductivityen_AU
dc.titleBeyond the ionic radii: A multifaceted approach to understand differences between the structures of LnNbO4 and LnTaO4 fergusonitesen_AU
dc.typeJournal Articleen_AU
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