Evolution of Structure in the Incommensurate Modulated LaNb1 -xWxO4+ x/2 (x = 0.04-0.16) Oxide Ion Conductors

Cheng Li, Stevin S. Pramana, Ryan D. Bayliss, Clare P. Grey, Frédéric Blanc, Stephen J. Skinner

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Hyper-stoichiometric CeNbO4+d phases demonstrate remarkable oxygen diffusivity and provide an interesting structural template for oxygen ion conductors. Previously, we have reported the room temperature structure of the incommensurate modulated LaNb0.88W0.12O4.06, a structural analogue of CeNbO4+d. We have confirmed that it is a pure oxygen ion conductor, with anions diffusing via an interstitialcy mechanism. However, the high temperature structural information for the LaNb1-xWxO4+d (x = 0.04-0.16) family, which is key to understanding the structure-property relationship in oxygen ionic conductors with complex structures at operating conditions, is unreported. In this contribution, we address this question by investigating the high temperature structural evolution of the LaNb1-xWxO4+2/x phases using a combination of thermal analysis, scattering techniques, and 17O and 93Nb nuclear magnetic resonance spectroscopy. We reveal a series of phase transitions between a modulated monoclinic phase, a high temperature modulated tetragonal phase, and a high temperature unmodulated tetragonal phase. These findings are correlated with the ion transport and offer insights into the design of new materials for solid state electrochemical devices.

Original languageEnglish
Pages (from-to)2292-2303
Number of pages12
JournalChemistry of Materials
Volume32
Issue number6
DOIs
StatePublished - Mar 24 2020

Funding

The authors acknowledge funding from the EPSRC for a studentship to R.D.B., the EU Marie Curie actions for an International Incoming Fellowship 2011-2013 (Grant 275212) to F.B., Clare Hall at the University of Cambridge for a Research Fellowship to F.B., and the EU ERC for an Advanced Fellowship (LIBNMR) to C.P.G. We thank Matthew T. Dunstan for recording the XRD patterns of O enriched LaNbO and LaNbWO. We gratefully acknowledge the Science and Technology Facilities Council (STFC) for access to neutron beamtime at HRPD, ISIS (RB1410098). The UK 850 MHz solid-state NMR Facility used in this research was funded by EPSRC and BBSRC, as well as the University of Warwick including via part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF). Collaborative assistance from the 850 MHz Facility Manager (Dr. Dinu Iuga, University of Warwick) is acknowledged. 17 4 0.84 0.16 4.08

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