Quenching-assisted actuation mechanisms in core–shell structured BiFeO3–BaTiO3 piezoceramics. Issue 33 (6th August 2019)

• Record Type: Journal Article
• Authors: Calisir, Ilkan; Kleppe, Annette K.; Feteira, Antonio; Hall, David A.
• Is Part Of: Journal of materials chemistry. Volume 7:Issue 33(2019)
• Page Start: 10218
• Page End: 10230
• Publication Date: 2019-08-06
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc01583c
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : An alternative actuation mechanism has been revealed via in situ X-ray diffraction experiments in core–shell structured BiFeO3 –BaTiO3 piezoceramics. Abstract : Electromechanical actuation in piezoceramics is usually enhanced by creating chemically homogeneous materials with structurally heterogeneous morphotropic phase boundaries, leading to abrupt changes in ion displacement directions within the perovskite unit cell. In the present study, an alternative mechanism to enhance electromechanical coupling is found in both chemically and structurally heterogeneous BiFeO3 –BaTiO3 lead-free piezoceramics. Such a mechanism is observed in a composition exhibiting core–shell type microstructure, associated with donor-type substitution of Ti 4+ for Fe 3+, and is primarily activated by thermal quenching treatment. Here, we describe the use of in situ high-energy synchrotron X-ray powder diffraction upon the application of a high electric field to directly monitor the ferroelectric and elastic interactions between these composite-like components, formed as core and shell regions within grains. Translational short or long-range ordering is observed in the BiFeO3 -depleted shell regions which undergo significant structural alterations from pseudocubic Pm 3̄ m relaxor-ferroelectric in slow-cooled ceramics to rhombohedral R 3 c or R 3 m with long-range ferroelectric order in the quenched state. The strain contributions from each component are calculated, leading to the conclusion that the total macroscopic strain arises predominantly from the transformed shell after quenching. Such observations are also complemented by investigations of microstructure and electrical properties, including ferroelectric behaviour and temperature-dependent dielectric properties.