Local Structure and Order-Disorder Transitions in "empty" Ferroelectric Tetragonal Tungsten Bronzes

Jason A. McNulty, David Pesquera, Jonathan Gardner, Andrei Rotaru, Helen Y. Playford, Matthew G. Tucker, Michael A. Carpenter, Finlay D. Morrison

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

The "empty"tetragonal tungsten bronze Ba4La0.67□1.33Nb10O30 displays both relaxor-like and normal dielectric anomalies as a function of temperature; the former is associated with loss of ferroelectricity and was proposed to originate from anion disordering [Chem. Mater. 2016, 28, 4616-4627]. Here we present total neutron scattering and pair distribution function (PDF) analysis, which shows an increase in the distribution of oxygen-oxygen distances at the relaxor transition and which supports the proposed anion disordering mechanism. The disordering process can be destabilized by reducing the average A-cation size (i.e., Nd-doping: Ba4(La1-xNdx)0.67Nb10O30); this introduces a more strongly propagating tilt system in line with the previously reported crystal-chemical framework model [Chem. Mater. 2015, 27, 3250-3261]. Mechanical loss data obtained using resonant ultrasound spectroscopy also indicate destabilization of the disordering process with increasing Nd-substitution.

Original languageEnglish
Pages (from-to)8492-8501
Number of pages10
JournalChemistry of Materials
Volume32
Issue number19
DOIs
StatePublished - Oct 13 2020

Funding

J.A.M. would like to acknowledge the School of Chemistry, University of St. Andrews, for the allocation of a Ph.D. studentship through the EPSRC doctoral training grant (EP/K503162/1). A.R. would like to acknowledge support through the Strategic Grant POSDRU/159/1.5/S/133255, Project ID 133255 (2014), cofinanced by the European Social Fund within the Sectorial Operational Program Human Resources Development 2007–2013 and also the University of Craiova and University of Cambridge for the mobility grant “Resonant ultrasound spectroscopy (RUS) characterization of dielectric and ferroelectric tetragonal tungsten bronzes”. The work carried out at the University of St. Andrews and University of Cambridge is part of an EPSRC-funded collaboration (EP/P02453X/1 and EP/P024904/1). We would like to thank the Science and Technology Facilities Council (STFC) for access to the Polaris beamline at the ISIS neutron source (experiment RB152073, DOI: 10.5286/ISIS.E.RB1520173). The research data (and/or materials) supporting this publication can be accessed at DOI: 10.17630/963073a9-a4de-43a9-93e3-b415acd2c089.

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