Controlling mixed conductivity in Na1/2Bi1/2TiO3 using A-site non-stoichiometry and Nb donor-doping

Li, Linhao; Li, Ming; Zhang, Huairuo; Reaney, Ian M.; Sinclair, Derek C.

Abstract

Precise control of electronic and/or ionic conductivity in electroceramics is crucial to achieve the desired functional properties as well as to improve manufacturing practices. We recently reported the conventional piezoelectric material Na1/2Bi1/2TiO3 (NBT) can be tuned into a novel oxide-ion conductor with an oxide-ion transport number (tion) 4 0.9 by creating bismuth and oxygen vacancies. A small Bi-excess in the nominal starting composition (Na0.50Bi0.50+xTiO3+3x/2, x = 0.01) or Nb-donor doping (Na0.50Bi0.50Ti1_yNbyO3+y/2, 0.005 less than or equal Y less than or equal 0.030) can reduce significantly the electrical conductivity to create dielectric behaviour by filling oxygen vacancies and suppressing oxide ion conduction (tion less than or equal 0.10).
Here we show a further increase in the starting Bi-excess content (0.02 less than or equal X less than or equal 0.10) reintroduces significant levels of oxide-ion conductivity and increases tion ~ 0.4–0.6 to create mixed ionic/electronic behaviour. The switch from insulating to mixed conducting behaviour for x > 0.01 is linked to the presence of Bi-rich secondary phases and we discuss possible explanations for this effect. Mixed conducting behaviour with tion ~ 0.5–0.6 can also be achieved with lower levels of Nb-doping ( y ~ B 0.003) due to incomplete filling of oxygen vacancies without the presence of secondary phases. NBT can now be compositionally tailored to exhibit three types of electrical behaviour; Type I (oxide-ion conductor); Type II (mixed ionic-electronic conductor); Type III (insulator) and these results reveal an approach to fine-tune tion in
NBT from near unity to zero. In addition to developing new oxide-ion and now mixed ionic/electronic NBT-based conductors, this flexibility in control of oxygen vacancies allows fine-tuning of both the dielectric/piezoelectric properties and design manufacturing practices for NBT-based multilayer piezoelectric devices.

• Journal Article Type: Article
• Acceptance Date: May 20, 2016
• Online Publication Date: May 20, 2016
• Publication Date: Jun 28, 2016
• Deposit Date: Jul 25, 2018
• Publicly Available Date: Jan 14, 2019
• Journal: Journal of Materials Chemistry C
• Print ISSN: 2050-7526
• Electronic ISSN: 2050-7534
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 4
• Issue: 24
• Pages: 5779-5786
• DOI: https://doi.org/10.1039/c6tc01719c
• Public URL: http://dx.doi.org/10.1039/C6TC01719C
• Publisher URL: https://pubs.rsc.org/en/Content/ArticleLanding/2016/TC/C6TC01719C#!divAbstract
• Additional Information: : This document is Similarity Check deposited; : Linhao Li (ORCID); : Linhao Li (ResearcherID); : The Royal Society of Chemistry has an exclusive publication licence for this journal; OPEN ACCESS: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0); : Single-blind; : Received 27 April 2016; Accepted 20 May 2016; Accepted Manuscript published 20 May 2016; Advance Article published 31 May 2016; Version of Record published 16 June 2016