Multi elements substituted Aurivillius phase relaxor ferroelectrics using high entropy design concept

• Published in: Materials & design 2021-02, Vol.200, p.109447, Article 109447
• Main Authors: Zhang, Man, Xu, Xinzhao, Yue, Yajun, Palma, Matteo, Reece, Michael J., Yan, Haixue
• Format: Article
• Language: English
• Subjects: Aurivillius phase; Domain; High entropy; Nano domains; Relaxor ferroelectric
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2020.109447

The concept of high entropy ceramics opens up the possibility to optimise the properties of relaxor ferroelectrics with Aurivilius phase structures. In this paper, two new multi-element substituted Aurivillius phase ceramics, (Ca0.25Sr0.25Ba0.25Pb0.25)Bi2Nb2O9 and (Ca0.2Sr0.2Ba0.2Pb0.2Nd0.1Na0.1)Bi2Nb2O9 are prepared. Both ceramics are single phase, exhibiting orthorhombic symmetry with space group A21am at room temperature. The frequency dependence of the temperature of the dielectric permittivity peak, Tm, shows relaxor behaviour for both ceramics. Multi-domain configurations, including long range ordered ferroelectric domains and nano domains, were observed using piezoresponse force microscopy (PFM). Under an applied DC field, the nano domains irreversibly transformed to micro-meter sized domains, which is consistent with the Vogel-Fulcher Law fitted results that show that the freezing temperatures of the two ceramics are above room temperature. Their improved piezoelectric constant is attributed to their low coercive fields, which are related to the multi domain configurations in the Aurivillius phase relaxor ferroelectrics. [Display omitted] •Two single phase BaBi2Nb2O9 - based Aurivillius phase ceramics have been developed using the high entropy ceramic concept.•The developed ceramics are relaxor ferroelectrics with dielectric loss six times lower compared with BaBi2Nb2O9.•The freezing temperatures of the developed BaBi2Nb2O9 based ceramics increased from −155 °C to above 300 °C.•The optimized performance of the developed ceramics is related to their multi-domain configurations.