Ferroelectric Aging Effect Research Articles

Large Electrostrain from the Ferroelectric Aging Effect around a Morphotropic Phase Boundary

A large electrostrain of ∼0.245% emerged in an intrinsic-acceptor-doped morphotropic phase boundary (MPB) system Ba(Ce0.1Ti0.9)O3–x(Ba0.7Ca0.3)TiO3 under an electric field of 30 kV/cm at 0.1 Hz. It...

Ferroelectric aging effects and large recoverable electrostrain in ceria‐doped BaTiO3 ceramics

AbstractFerroelectric aging is a phenomenon that is generally observed in acceptor‐doped ferroelectrics and usually produces a large recoverable electrostrain. In this work, using an oxide ionic conducting material, a Gd‐modified ceria solution (GDC), as a dopant, we find that GDC‐doped BaTiO3 ceramics exhibit ferroelectric aging behaviors at room temperature. These ceramics show double polarization hysteresis (P‐E) loops and sprout‐shaped recoverable strain vs electric field (S‐E) curves. GDC‐doped BT ceramic (3 mol%) produces a large recoverable electrostrain of 0.12% at 3 kV/cm. The large ions of Ce3+ and Gd3+, which have small electronegativity, lead to the high mobility of oxygen vacancies and a rapid symmetry conformation for short range ordering (SC‐SRO) of points defects, which appear as fast aging effects and a large electrostrain in GDC‐doped BT ceramics at room temperature.

3D Imaging of Ferroelectric Kinetics during Electrically Driven Switching.

Čerenkov-type second-harmonic generation microscopy is used for in situ 3D imaging of the switching process of ferroelectric domains in a relaxor-type ferroelectric crystal. The lateral and longitudinal domain wall motion is optically measured and compared with the hysteresis loop to reveal the connection between the domain kinetics and the ferroelectric aging effect in strontium barium niobate.

Nonmonotonic variation of aging behavior in Fe-doped BaTiO3 ceramics

The investigation of ferroelectric aging effect in Fe-doped BaTiO3 ceramics reveals that such effect is first strengthened and then suppressed with the increase content of Fe dopant. Such nonmonotonic variation of aging behavior is considered to be originated from the competition effects between increased concentration of oxygen vacancies and decreased c/a value on the formation of defect dipoles (FeTi′−Vo··)·. This study provides a feasible alternative method for modulating aging effect and will favor the applications of ferroelectrics.

Defect-dipole-induced two important macroscopic effects: The dielectric relaxation and the ferroelectric aging in hybrid-doped (Ba,Ca)TiO3 ceramics

To observe the dielectric relaxor behavior and the ferroelectric aging effect, the structural and electrical properties of (Ba0.90Ca0.10)(Ti1−xCax)O3−x (BCT-C) ceramics prepared using a conventional dry route were investigated. With increased concentration of Ca on the B-site in BCT-C ceramics, the tetragonal phase is decreased while the multiphases with the cubic pervoskite structure as a major constituent is increased and remained predominant in the BCT-C ceramics with x>0.03. The increased amount of Ca on the B-site causes the high temperature phase transition to shift to the low temperature and results in an increase in the degree of diffusion and relaxation of the BCT-C ceramics. The observed dielectric relaxation behavior may be understood by a defect-dipole formed random electric field induced domain state. The aging effect controlled by the migration of mobile oxygen vacancies is rarely observed in aged BCT-C ceramics while it can be markedly observed in Bi-doped BCT ceramics. Based on the microscopic mechanism of the aging effect, the possible reasons for the aging effect are given.

Ferroelectric aging behaviors of BaTi0.995Mn0.005O3 ceramics: grain size effects

We report the ferroelectric aging effect of dense BaTi0.995Mn0.005O3 ceramics with grain size varying from 2000 nm to 150 nm. Given the identical aging process, it is revealed that the significant aging effect with clear double-hysteresis loop, observed in coarse-grain sample, is substantially suppressed with decreasing grain size. This suppression can be attributed to the reduction of tetragonal distortion and the grain boundary barrier effect in fine-grain sample. Consequently, the weak thermodynamic driving force and the limited kinetic migration are unfavorable to a reversible domain switching, resulting in a normal hysteresis loop in small grained samples.

Physical Properties and Electrical Aging Effects in Fe3+/Nb5+ Hybrid-Doped Barium Titanate Ceramics

It is well known that acceptor and donor doping results in opposite ferroelectric aging effects; however, the aging effects in hybrid-doped (acceptor+donor) materials has remained mysterious. Thus, the aging behavior of dielectric and ferroelectric properties in Fe 3+ /Nb 5+ hybrid-doped BaTiO 3 ceramics was investigated in this study. The concentration of acceptor dopant (Fe 3 + ) was fixed at 1 mol%, while that of donor dopant (Nb 5+ ) was varied from 0.5–2.0 mol%. The SEM and XRD techniques were used to study the microstructure and phase formation, respectively. The results showed that the dielectric properties of all de-aged samples decreased exponentially with time. The aged samples with 0.5 and 1.0 mol% Nb 5+ obviously showed constricted hysteresis loops, while those with higher concentration of Nb 5+ (1.5–2.0 mol%) showed normal hysteresis loops. The explanations based on the effects of defect dipole were discussed.

Ferroelectric and Dielectric Aging Effects of Fe<sup>3+</sup>/Nb<sup>5+</sup> Hybrid-Doped Barium Titanate Ceramics

It is well known that acceptor and donor doping results in opposite ferroelectric aging effects; however, the aging effects in hybrid-doped (acceptor+donor) has remained unclear. Thus, the aging effect of dielectric and ferroelectric properties in Fe3+/Nb5+ hybrid-doped BaTiO3 ceramics was investigated in this research. The concentration of acceptor dopant (Fe3+) was fixed at 1 mol% while that of donor dopant (Nb5+) was varied from 0.5-2.0 mol%. XRD technique was used to study the phase morphology. Before measuring dielectric and ferroelectric aging effect, all samples were deaged at 250 °C for 1 hour. The results showed that the dielectric properties of all deaged samples have decreased exponentially with time. The deaged samples with 0.5 and 1.0 mol% of Nb5+ obviously showed double hysteresis loop while that with higher concentration of Nb5+ (1.5-2.0 mol%) showed the rectangular (normal) hysteresis loop. The explanations based on the effect of defect dipole were discussed.

Striking similarity of ferroelectric aging effect in tetragonal, orthorhombic and rhombohedral crystal structures

A series of Mn-doped alkaline niobate-based and lead zirconic titanate ferroelectrics that possess tetragonal, orthorhombic, and rhombohedral perovskite structures was fabricated, and the aging behavior of their hysteresis loop and electrostrain was studied. We found that after aging, all the samples showed a similar double hysteresis loop and large recoverable electrostrain behavior, regardless of their crystal structure and of their ionic species. The striking similarity of the aging effect in different ferroelectric phases suggests that there exists a common physical origin of aging in ferroelectric perovskites. Based on a symmetry-conforming short-range ordering mechanism of point defects, we provided a unified microscopic explanation for the aging effect in the tetragonal, orthorhombic, and rhombohedral ferroelectrics.

Aging Effect on Lanthanum Doped Ferroelectric Lead Titanate Ceramics

Ferroelectric devices are widely applied in many fields, such as energy conversion and communication. The aging effect in ferroelectric materials plays a central role in the reliability of the related equipments. But it is very difficult to understand the origin of aging effect in ferroelectrics because these materials possess different defects and exhibit various aging behavior. The reverse transition temperature in lead titanate doped with lanthanum increases during aging at ferroelectric phase was reported. It is well known that lattice defects, such as vacancies and solute atoms, are ubiquitous in crystalline solids. These point defects affect physical properties in ferroelectrics significantly. The abnormal increase of the reverse transition temperature was discussed in terms of diffusion of point defects during aging. Dielectric performance in the material after aging was measured and discussed as well.

Ferroelectric aging effect in hybrid-doped BaTiO3 ceramics and the associated large recoverable electrostrain

Acceptor doping and donor doping have been known to result in opposite ferroelectric aging effects, but the aging effect of hybrid-doped (acceptor+donor) ferroelectrics has remained unclear. In this letter the authors report the aging effect in Mn3++Nb5+ hybrid-doped BaTiO3 ceramics with acceptor fixed at 1mol% but with donor varied from 0.5to2mol%. The authors found surprisingly that ferroelectric aging existed in all the samples, no matter which of the two, acceptor or donor, was dominant: all the samples showed a double hysteresis loop after aging, but with increasing donor (Nb5+) concentration the coercive field and hysteresis decrease. Meanwhile, a large nonlinear recoverable electrostrain up to 0.17% (due to reversible domain switching) was observed at 3kV∕mm, which exceeded that of acceptor-monodoped ceramics and was about twice the piezoelectric strain of hard lead zirconate titanate. These results demonstrate that hybrid doping is an effective way to enhance the domain-switching-related electrostrain properties. Finally, the aging effect of hybrid-doped ferroelectrics was explained.

Aging in Ferroelectrics

The reorientation of defect dipoles and the drift of free charge carriers are the most prominent microscopic mechanisms under discussion to provoke the aging effect in ferroelectrics. These two mechanisms are contrasted taking into account the influence of grain boundaries in a polycrystalline material. For the drift model, clamping pressures on domain walls only depend on geometry and on the transport properties of the mobile defect charge carrier independent of its electronic or ionic nature. For a numerical example clamping pressures as a result of drift of oxygen vacancies are determined in BaTiO3. They range from 106 to 107 Pa corresponding to experimental values.