Revealing the role of local stress on the depolarization of BNT-BT-based relaxors

Abstract

Canonical relaxors exhibit an electric-field-induced phase transition between a macroscopically nonpolar and polar phase that can be tuned from being stable at low temperature to being reversible at high temperature.The reversibility of this phase change determines the electromechanical performance and large strains can be achieved if the polar phase is intrinsically unstable. This paper is on the thermal depolarization characteristics of a BNT-BT-based multiphase relaxor ceramic observed through the transition temperature from field-induced polar to nonpolar state. It is shown that the progress of detexturization strongly depends on the crystallographic phase. In the more susceptible phase, it becomes significant about 40°C below the macroscopically observed transition temperature. Additionally, the surface domain structure vanishes at lower temperatures than expected from both dielectric and structural measurements. The development of strong interfacial stresses aiding depolarization, and a mismatch in chemical pressure between surface and bulk, are discussed as the origins for the observed effects. Tailoring of interfacial stresses through chemical adaption of crystallographic phase fractions opens up a pathway to optimize the strain performance of actuator materials and can become a useful tool to stabilize metastable crystallographic phases as well as for property tuning in piezotronics, Mott insulators and multiferroics.

Phase evolution and strong temperature‐dependent electrostrictive effect in (1−x)Pb(Mg1/3Nb2/3)O3‐xPbTiO3 solid solutions

“…As the temperature increases, the position of the peak shifts to the lower E ‐field direction. More crucially, at T PN , the current peak splits into two peaks identified as E pos and E neg , suggesting that the depolarization process in polarization reversal differs from that in polarization establishment 4,65 . When the temperature rises to about T FR , the E neg peak crosses through the zero of the x axis and continues to move in the opposite direction.…”

“…More crucially, at T PN , the current peak splits into two peaks identified as E pos and E neg , suggesting that the depolarization process in polarization reversal differs from that in polarization establishment. 4,65 When the temperature rises to about T FR , the E neg peak crosses through the zero of the x axis and continues to move in the opposite direction. T N is the temperature at which the E neg peak crosses through the zero of the x axis.…”

Electric field-induced transformations in bismuth sodium titanate-based materials

“…Additional factors that influence the thermal depolarization process might be represented by the stresses developed at the interfaces between different crystallographic phases, which promote depolarization, and by the chemical pressure, which tends to stabilize the domain structure [196]. Various strategies have been developed to enhance the temperature stability of the piezoelectric properties in BNT-based ceramics [143], including composition variations [82,[197][198][199][200][201], grain size modification [202] and quenching treatments after sintering [201,203,204].…”

Spontaneous ferroelectric order in lead-free relaxor Na1/2Bi1/2TiVenkataraman1, Hinterstein2, Lee3 et al. 2020Phys. Rev. BSelf Cite15000View full textAdd to dashboardCite

“…Relaxors, characterized by site and charge disorder associated with local polar heterogeneities, find applications as electromechanical actuators that exploit the giant strains exhibited by these systems, often resulting from phase transformations [3][4][5][6][7]. These transformations commonly take place upon application of an external stimulus, e.g., temperature, stress or electric field [4,[8][9][10][11]. Although the majority of prior research focuses on the phase transformations that result in colossal strains in relaxor systems and related correlation to the structure and microstructure [12,13], relatively little attention has been devoted to understanding the spontaneous ferroelectric order in these systems.…”