Nanofragmentation of Ferroelectric Domains During Polarization Fatigue

Abstract

The microscopic mechanism for polarization fatigue in ferroelectric oxides has remained an open issue for several decades in the condensed matter physics community. Even though numerous models are proposed, a consensus has yet to be reached. Since polarization reversal is realized through ferroelectric domains, their behavior during electric cycling is critical to elucidating the microstructural origin for the deteriorating performance. In this study, electric field in situ transmission electron microscopy is employed for the first time to reveal the domain dynamics at the nanoscale through more than 103 cycles of bipolar fields. A novel mechanism of domain fragmentation is directly visualized in polycrystalline [(Bi1/2Na1/2)0.95Ba0.05]0.98La0.02TiO3. Fragmented domains break the long‐range polar order and, together with domain wall pinning, contribute to the reduction of switchable polarization. Complimentary investigations into crystal structure and properties of this material corroborate our microscopic findings.

Disrupting long-range polar order with an electric field

“…Unlike the dynamically fluctuating polar nanoregions in ergodic relaxors [22,23], the static polar nanodomains shown in Fig. 1b can be irreversibly poled and aligned [31,36]. After poling at 60 kV/cm, a well-defined depolarization temperature T d was observed in the dielectric curves (Fig.…”

“…We reveal this unusual phase transition in a lead-free relaxor composition of [(Bi 1/2 Na 1/2 ) 0.95 Ba 0.05 ] 0.98 La 0.02 TiO 3 (BNT2La) in which a ferroelectric phase can be readily formed during electric poling [30,31]. The induced ferroelectric phase remains metastable upon field removal.…”

“…In situ TEM experiments were carried out on a specimen that was crack-free at the edge of the central perforation on a Phillips CM30 microscope operated at 200 kV. Detailed experimental setup can be found in previous literature [6,21,31].…”

Cyclic electric field response of morphotropic Bi1/2Na1/2TiO3-BaTiO3 piezoceramics

“…The presence of domains is visible in both compositions. A recently performed in situ electric-field TEM investigation on lanthanum doped BNT-5BT 35 supported the idea of evolving domain configurations as salient features in the fatigue processes. 36 In BNT-6BT, a high amount of grains feature a core-shell structure.…”

Giant strain with low cycling degradation in Ta-doped [Bi1/2(Na0.8K0.2)1/2]TiO3 lead-free ceramics

“…In contrast, P r slowly increases with N within the first 100 cycles, which may be a sign of stabilization of the ferroelectric phase through accumulation of charged point defects during electric cycling. 33 It is interesting to note that the internal bias field tends to display an opposite trend to the coercive field, E c . Meanwhile, S þ,max gradually decreases to 0.55% after 10 000 cycles of bipolar fields of 650 kV/cm (an 11% reduction from 0.62%), indicating a good resistance of BNT-1.5Ta to cycling degradation.…”