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Abstract: The relationship between the piezoelectric properties and the structure/microstructure for 0.05Bi(Mg2/3Nb1/3)O3‐(0.95‐x)BaTiO3‐xBiFeO3 (BBFT, x = 0.55, 0.60, 0.63, 0.65, 0.70, and 0.75) ceramics has been investigated. Scanning electron microscopy revealed a homogeneous microstructure for x < 0.75 but there was evidence of a core‐shell cation distribution for x = 0.75 which could be suppressed in part through quenching from the sintering temperature. X‐ray diffraction (XRD) suggested a gradual structural transition from pseudocubic to rhombohedral for 0.63 < x < 0.70, characterized by the coexistence of phases. The temperature dependence of relative permittivity, polarization‐electric field hysteresis loops, bipolar strain‐electric field curves revealed that BBFT transformed from relaxor‐like to ferroelectric behavior with an increase in x, consistent with changes in the phase assemblage and domain structure. The largest strain was 0.41% for x = 0.63 at 10 kV/mm. The largest effective piezoelectric coefficient (d33*) was 544 pm/V for x = 0.63 at 5 kV/mm but the largest Berlincourt d33 (148 pC/N) was obtained for x = 0.70. We propose that d33* is optimized at the point of crossover from relaxor to ferroelectric which facilitates a macroscopic field induced transition to a ferroelectric state but that d33 is optimized in the ferroelectric, rhombohedral phase. Unipolar strain was measured as a function of temperature for x = 0.63 with strains of 0.30% achieved at 175°C, accompanied by a significant decrease in hysteresis with respect to room temperature measurements. The potential for BBFT compositions to be used as high strain actuators is demonstrated by the fabrication of a prototype multilayer which achieved 3 μm displacement at 150°C. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ceramics of solid solutions (1 − x) BaTiO3- x( Bi1/2A1/2) TiO3 (A = Ag, Li, Na, K, Rb, Cs, x ≤ 0.20) were prepared and their crystal structures, dielectric, ferroelectric, and piezoelectric properties were investigated. It was found that ( Bi1/2A1/2) TiO3-type doping compounds broadened the temperature range of the tetragonal phase in BaTiO3 and all the compositions examined displayed a tetragonal structure at room temperature. The Curie temperature ( TC) was observed to increase with respect to pure BaTiO3 to the range 140°C-210°C through solid solution. Remanent polarization ( Pr) tended to decrease with increased content of doping compound, whereas the coercive field ( EC) rose and piezoelectric coefficient ( d33) fell. The highest d33 value in the solid solutions was observed in 0.97 BaTiO3-0.03( Bi1/2 Ag1/2) TiO3 at 90 pC/N. [ABSTRACT FROM AUTHOR]

A comprehensive review on the latest development of the antiferroelectric ↔ ferroelectric phase transition is presented. The abrupt volume expansion and sudden development of polarization at the phase transition has been extensively investigated in PbZrO3-based perovskite ceramics. New research developments in these compositions, including the incommensurate domain structure, the auxetic behavior under electric fields in the induced ferroelectric phase, the ferroelastic behavior of the multicell cubic phase, the impact of radial compression, the unexpected electric field-induced ferroelectric-to-antiferroelectric transition, and the phase transition mechanical toughening effect have been summarized. Due to their significance to lead-free piezoelectric ceramics, compounds with antiferroelectric phases, including NaNbO3, AgNbO3, and ( Bi1/2Na1/2) TiO3, are also critically reviewed. Focus has been placed on the ( Bi1/2Na1/2) TiO3- BaTiO3 solid solution where the electric field-induced ferroelectric phase remains even after the applied field is removed at room temperature. Therefore, the electric field-induced antiferroelectric-to-ferroelectric phase transition is a key to the poling process to develop piezoelectricity in morphotropic phase boundary ( MPB) compositions. The competing phase transition and domain switching processes in 0.93( Bi1/2Na1/2) TiO3-0.07 BaTiO3 are directly imaged with nanometer resolution using the unique in situ transmission electron microscopy ( TEM) technique. [ABSTRACT FROM AUTHOR]

The 1:1 structural order and B-site cation order in Pb(Mg1/3Nb2/3)O3 ceramics was significantly enhanced by Zr4+ substituting Nb5+ according to the chemical formula Pb(Mg1/3Zr2 x/3Nb2(1− x)/3)O3− x/3. The enhanced structural and cation order was revealed by both X-ray diffraction and transmission electron microscopy. The increased charge difference and the introduced oxygen vacancies were suggested to account for the observed long-range cation order. Typical relaxor ferroelectric behavior was retained even in the ceramics with a high degree of cation order. [ABSTRACT FROM AUTHOR]

The ternary system of lead nickel niobate Pb(Ni[sub1/3]Nb[sub2/3])O[sub3] (PNN), lead zinc niobate pb(Zn[sub1/3]Nb[sub2/3])O[sub3] (PZN), and lead zirconate titanate Pb(Zr[sub1/2]Ti[sub1/2])O[sub3] (PZT) was investigated to determine the influence of different solid state processing conditions on dielectric and ferroelectric properties. The ceramic materials were characterized using x-ray diffraction, dielectric measurements, and hysteresis measurements. To stabilize the perovskite phase, the columbite route was utilized with a double crucible technique and excess PbO. The phase-pure perovskite phase of PNN-PZN-PZT ceramics was obtained over a wide compositional range. It was observed that for the ternary system 0.5PNN-(0.5 - x)PZN-xPZT, the change in the transition temperature (T[subm]) is approximately linear with respect to the PZT content in the range x = 0 to 0.5. With an increase in x, T[subm] shifts up to high temperatures. Examination of the remanent polarization (Pr) revealed a significant increase with increasing x. In addition, the relative permittivity (ε[subr]) increased as a function of x. The highest permittivities (ε[subr] = 22,000) and the highest remanent polarization (P[subr] = 25 μC/cm²) were recorded for the binary composition 0.5Pb(Ni[sub1/3]Nb[sub2/3])O[sub3]-0.5Pb(Zr[sub1/2]Ti[sub1/2])O[sub3]. [ABSTRACT FROM AUTHOR]

The field-driven in-situ transmission electron microscopy (TEM) technique was developed to examine micromechanisms of field-induced cracking in ferroelectric ceramics. The technique was constructed by combining a selectively deposited thin film electrode configuration with a modified hot stage to deliver a required electric voltage to a ferroelectric TEM specimen. Under cyclic electric fields, microcracks were found to initiate from pores at the triple junctions and propagate along the grain-boundary in a lead zirconate titanate (PZT) ceramic. Grain-boundary cavitation and coalescence of microcracks were directly observed for the first time during field-induced fracture of PZT at room temperature. The results suggest that dielectric breakdown of the grain-boundary phase was conducive to grain-boundary cavitation, and the crack growth followed the progressive accumulation of the cavity density with electric cycling. [ABSTRACT FROM AUTHOR]

A solid-state memory effect is defined as the ability of a material to store information, and it requires at least two switchable memory states that can be addressed by an externally controlled parameter. In this article we present experimental evidence of a memory effect in anti-ferroelectric Pb 0.99 Nb 0.02 [(Zr 0.57 Sn 0.43 ) 0.94 Ti 0.06 ] 0.98 O 3 polycrystalline ceramic materials. This study indicates that anti-ferroelectrics encode data in their ferroelectric sublattices, resulting in a 4-state memory capable of storing 2 digital bits simultaneously. This result opens up the possibility of realizing non-volatile anti-ferroelectric random access memory, as well as other possible devices and logic applications based on anti-ferroelectric materials. [ABSTRACT FROM AUTHOR]

Defects are essential to engineering the properties of functional materials ranging from semiconductors and superconductors to ferroics. Whereas point defects have been widely exploited, dislocations are commonly viewed as problematic for functional materials and not as a microstructural tool. We developed a method for mechanically imprinting dislocation networks that favorably skew the domain structure in bulk ferroelectrics and thereby tame the large switching polarization and make it available for functional harvesting. The resulting microstructure yields a strong mechanical restoring force to revert electric field–induced domain wall displacement on the macroscopic level and high pinning force on the local level. This induces a giant increase of the dielectric and electromechanical response at intermediate electric fields in barium titanate [electric field–dependent permittivity (e33) ≈ 5800 and large-signal piezoelectric coefficient (d33*) ≈ 1890 picometers/volt]. Dislocation-based anisotropy delivers a different suite of tools with which to tailor functional materials. [ABSTRACT FROM AUTHOR]

Ceramics solid solutions within the binary system of xPb(Zn1/3Nb2/3)O3−(1−x)Pb(Zr1/2Ti1/2)O3 with x=0.1–0.5 were synthesized via the mixed oxide method and the columbite method. Phase development of calcined powders and the crystal structure of sintered ceramics were analyzed by X-ray diffraction. Ferroelectric properties were measured to elucidate the phase transformation and identify the impact of the processing conditions. It is shown that there was no significant difference in Pr across the composition range. However, the coercive field Ec was shown to exhibit a strong compositional dependence. Compared with ceramics prepared by the columbite method, ceramics prepared by the mixed oxide method showed a lower remanent polarization Pr and a higher coercive field Ec. In addition, both X-ray diffraction and ferroelectric measurements indicated a phase transformation from a tetragonal to a pseudo-cubic rhombohedral phase when the fraction of Pb(Zn1/3Nb2/3)O3 (PZN) was increased. The morphotropic phase boundary (MPB) is located between x=0.2 and 0.3 according to observations made on ceramics prepared with the columbite method. However, this transformation was obscured in the ceramics prepared with the mixed oxide method. It is proposed that compositional heterogeneities were responsible for these experimental investigations. [Copyright &y& Elsevier]