title: A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3.
abstract: Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm(-1) at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides.
authors.affiliation: Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University and JARA-FIT, D-52056 Aachen, Germany.
authors.forename: Martha J
authors.initials: MJ
authors.lastname: Pietrowski
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University and JARA-FIT, D-52056 Aachen, Germany.
authors.forename: Roger A
authors.identifier: 0000000177214128
authors.initials: RA
authors.lastname: De Souza
authors.affiliation: Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
authors.forename: Huairuo
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Reaney
authors.affiliation: Department of Materials, Imperial College London, London SW7 2AZ, UK.
authors.forename: Stuart N
authors.initials: SN
authors.lastname: Cook
authors.affiliation: 1] Department of Materials, Imperial College London, London SW7 2AZ, UK [2] International Institute for Carbon-Neutral Energy Research (I2CNER), 744 Motooka Nishi-ku Fukuoka 819-0395, Japan.
authors.forename: John A
authors.initials: JA
authors.lastname: Kilner
authors.affiliation: Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
authors.forename: Derek C
authors.initials: DC
authors.lastname: Sinclair