Strong ferroelectric domain-wall pinning in BiFeO3 ceramics

Abstract

We have studied the polarization-electric-field hysteresis, the dielectric permittivity dispersion, the piezoelectric properties, the electric-field-induced strain, and the interrelations between these properties for bismuth ferrite (BiFeO3) ceramics. The results indicate that the domain-wall movement in BiFeO3 is strongly inhibited by charged defects, most probably acceptor-oxygen-vacancy defect pairs. The domain-wall mobility can be considerably increased by preventing the defects from migrating into their stable configuration; this can be achieved by thermal quenching from above the Curie temperature, which freezes the disordered defect state. Similarly, Bi2O3 loss during annealing at high temperatures contributes to depinning of the domain walls and an increase in the remanent polarization. The possible defects causing the pinning effect are analyzed and discussed. A weakening of the contacts between the grains in the ceramics and crack propagation were observed during poling with constant field at 100 kV/cm. This is probably caused by an electrically induced strain associated with ferroelastic domain reversal. A relatively large piezoelectric d33 constant of 44 pC/N was obtained by “cyclic poling,” in which the electric field was released after each applied cycle with the purpose to relax the mechanical stresses and minimize the problem of cracking.

Piezoelectric nonlinearity and frequency dispersion of the direct piezoelectric response of BiFeO3 ceramics

“…10 In spite of the extensive research on BiFeO 3 and its chemical modifications, the knowledge of the piezoelectric response of pure BiFeO 3 ceramics is rather poor and usually only values of d 33 are reported, which range from 4 to 60 pm/V. [11][12][13][14] The reason for the large spread in the values is probably a combination of high electrical conductivity and high coercive field (50-85 kV/cm), which are strongly processing sensitive, 11,[15][16][17][18] and difficulties in processing the ferrite. [19][20][21] The problem of the high electrical conductivity, which prevents application of high electric fields to BiFeO 3 , is often overcome by measuring the electromechanical response only locally using piezoforce microscopy (PFM).…”

“…9,12,22 Using a mechanochemically assisted synthesis, we have recently succeeded to prepare BiFeO 3 ceramics with sufficiently low DC conductivity to withstand large electric fields, i.e., up to 180 kV/cm. 15 As a result of electric-field switching of domains, a large strain, comparable to 4 that achievable in Pb-based ferroelectric ceramics with MPB compositions, such as Pb(Zr,Ti)O 3 (PZT) and Pb(Mg,Nb)O 3 -PbTiO 3 (PMN-PT), was measured in these BiFeO 3 ceramics. 23 Those results suggested that the weak-field electromechanical response of the ferrite may also involve a considerable contribution of non-180° domain-wall movement.…”

Super-Lattice Structure and Phase Evolution of Pb(Lu0.5Nb0.5)O3-PbTiO3 Single Crystal with Low PbTiO3

“…This kind of double hysteresis loop has been found in various materials, such as Pb(Zr,Ti)O 3 [18], BiFeO 3 [19], and BaTiO 3 [20]. In these system, some types of inhomogeneity, structural disorder, and structural defects with local polarity are present in these materials, leading to the domain walls being strongly pinned by defects [18,19]. In addition, pinched hysteresis loops exhibit a small polarization for a zero electric field.…”

“…It is commonly believed that double hysteresis loops above the Curie temperature should be considered pinched hysteresis loops because there exist a region with some polar regions embedded in the non-polar matrix. This kind of double hysteresis loop has been found in various materials, such as Pb(Zr,Ti)O 3 [18], BiFeO 3 [19], and BaTiO 3 [20]. In these system, some types of inhomogeneity, structural disorder, and structural defects with local polarity are present in these materials, leading to the domain walls being strongly pinned by defects [18,19].…”

Multiferroic Materials: Physics and Properties

“…It was later shown that charged defects like oxygen vacancies impede the motion of domain walls, causing non-saturated ferroelectric hysteresis loops. 23 Quenching from above the ferroelectric transition temperature causes Figure 3 Crystal structure of a perovskite ABO 3 with a tetragonal ferroelectric distortion. randomization of the defects and yields saturated loops with respectable polarization values (B20 mC cm À2 ), but still not comparable to those achieved in thin films and single crystals.…”