Polarization twist in perovskite ferrielectrics

Abstract

Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms.

Electric-field-induced phase transition and pinched P–E hysteresis loops in Pb-free ferroelectrics with a tungsten bronze structure

“…A double P-E hysteresis loop can also be observed at temperatures slightly above the Curie temperature of the first-order ferroelectric transition, indicating the electric field-induced paraelectric-ferroelectric phase transition 15,16 . However, in the development of ferroelectric materials, a type of "pinched" P-E hysteresis loop with a constrained remanent polarization (P r ) value has been observed in various perovskite materials, e.g., Pb(Zr,Ti)O 3 solid solutions [17][18][19][20][21] , BiFeO 3 -based ceramics [22][23][24] , and (Bi 0.5 Na 0.5 )TiO 3 -based ceramics [25][26][27] . The main feature of the pinched P-E hysteresis loop is that the polarization, P r , for a zero electric field is small but finite, unlike ferroelectrics (large P r ) and antiferroelectrics (zero P r ) 9 .…”

“…Generally, the existence of pinched P-E hysteresis loops is attributed to strong domain wall pinning due to the diffusion of charged defects [17][18][19][20][21][22]25 . However, pinched P-E hysteresis loops can also be observed in defect-free ferroelectric materials, such as BiFeO 3 -based ceramics 23,24 and (Bi 0.5 Na 0.5 )TiO 3 -based ceramics 26 . In some cases of BiFeO 3 -based ceramics, the observed pinched P-E hysteresis loops are "simply" interpreted as the double P-E hysteresis loops of antiferroelectrics, and the concomitant enhancement in the piezoelectric response is attributed to an electric-field-induced transformation from a paraelectric orthorhombic phase to a polar rhombohedral phase 23 .…”

Pinched hysteresis loop in defect-free ferroelectric materials

“…1c can also be geometrically considered as being a linear combination between the hysteresis loops of FE and AFE materials represented in Figs 1a and 1b, respectively, and that these two latter loops are intrinsic in nature, it is legitimate to wonder whether pinched loops can also occur in defect-free systems -as also alluded in Ref. [13]. If that is the case, determining what types of phases could be involved in the pinched loops is also of importance to reveal possibly overlooked mechanisms, especially when realizing that observed pinched loops are sometimes "simply" interpreted to be double (antiferroelectric) hysteresis loops [14,15] and have been indicated to be associated with large piezoelectric response [13,14] via a novel mechanism coined "polarization twist" in Ref.…”

“…[13]. If that is the case, determining what types of phases could be involved in the pinched loops is also of importance to reveal possibly overlooked mechanisms, especially when realizing that observed pinched loops are sometimes "simply" interpreted to be double (antiferroelectric) hysteresis loops [14,15] and have been indicated to be associated with large piezoelectric response [13,14] via a novel mechanism coined "polarization twist" in Ref. [13].…”

Enhanced polarization properties of ferroelectric (Bi_1/2Na_1/2)TiO₃–Ba(Mg_1/3Nb_2/3)O₃ single crystals grown under high-pressure oxygen atmosphere

“…70), 71) The ferrielectric P4bm phase has been reported to display distinct types of structural behaviors such as a polarization twist under week fields 72) and E-induced phase transitions either to the R3c 70) 74) has a phase boundary between the R3c and P4bm phases at around a BMN content (x) of 45%. 75) Moreover, BNTBMN ceramics near the MPB composition present substantial polarization and strain properties arising from the E-induced phase transition between the P4bm and R3c phases.…”