Search

Electric field (E) control of magnetism is a persistent challenge in low-power consumption spintronic devices. A promising way to realize this control is to use the conversemagnetoelectric (ME) effect in insulating multiferroics.Here,we report considerable and repeatable E-modulated magnetization (M) at room temperature and even at 350 K via the significantly enhanced converseME effect near the morphotropic phase boundary (MPB) of the Cr-Mn co-doped (1-y)BiFe1-xCrxO3- yBaTi1-xMnxO3 (0.15 ≤ y ≤ 0.33, 0 ≤ x ≤ 0.03) solid solutions. In situ X-ray diffraction and Raman scattering experiments at different applied E for the sample near the MPB (i.e., y = 0.27, x = 0.03) show E-induced shift, broadening, and splitting in the {002}PC reflection, as well as a nearly monotonous variation in intensity of several phonon modes with E, reminiscent of the E-dependent M behavior. These results indicate that both E-induced lattice distortion and phase transformation dominate the converseME effects in these samples. Our demonstration of the E-regulation of magnetism via the E-sensitive crystal structures in designed insulating multiferroics near MPB may suggest a potential route to obtain efficient low-power spintronic devices. [ABSTRACT FROM AUTHOR]

Designing BiScO3‐PbTiO3 (BS–PT) ceramics that merge high Curie temperature (TC) and large piezoelectric coefficient (d33) has always been a significant challenge for high‐temperature applications. Doping is a commonly used and effective method for enhancing the electrical performances of piezoelectric ceramics. In this study, the Li+/W6+ acceptor–donor co‐doping method was used to enhance the piezoelectric properties of 0.36BiSc1‐xLixO3–0.64PbTi1‐yWyO3 (0.36x = 0.64y) ceramics. The optimal electrical performance was observed at x = 0.01 near morphotropic phase boundaries, with a large d33 (505 pC/N), high TC (407°C), huge remnant polarization (Pr ∼ 40.9 μC/cm2), and inverse piezoelectric coefficient (d33* = 601 pm/V). Rietveld refinement and piezoelectric force microscopy results revealed that incorporating Li+/W6+ into the BS–PT ceramics decreased the T phase proportion and domain size and increased the domain wall density. The enhancement in piezoelectricity can be attributed to the lowered energy barrier resulting from the reduced T‐phase proportion and complex domain structure, which promotes polarization rotation and facilitates domain wall motion. This work demonstrates that acceptor–donor co‐doping is a promising strategy for optimizing the electrical performance of the BS–PT ceramics. [ABSTRACT FROM AUTHOR]

BiFeO3–SrTiO3 (BF–ST) ceramics have been considered a novel class of lead‐free dielectric materials exhibiting notable dielectric constants and remarkable thermal stability. In this work, we fabricated a series of (1 − x)BF–xST (0.32 ≤ x ≤ 0.44) ceramics near the morphotropic phase boundary and comprehensively investigated their microstructure and electrical properties, which seeks to optimize the piezoelectric performance. As the ST content increases, a gradual reduction in the rhombohedral phase fraction is observed alongside a corresponding increase in the cubic phase fraction. Although x = 0.38, the maximum grain size of 5.66 μm is obtained, accompanied by a distinctive heterogeneous core–shell microstructure, which demonstrates a high remanent polarization of 51.2 μC/cm2 and a maximum d33 value of 72 pC/N. Furthermore, impedance spectroscopy analysis reveals the formation of a conductive core and a nonconductive shell within the sample. These findings highlight the potential of optimized BF–ST ceramics as promising alternatives to lead‐based piezoelectric materials, offering exceptional ferroelectric and piezoelectric properties. [ABSTRACT FROM AUTHOR]

A series of morphotropic phase boundary (MPB) compositions of (1–x)Na1/2Bi1/2TiO3‐xBaTiO3 (x = 0.05, 0.055, 0.06, 0.065, 0.07), with and without 0.5 mol% Zn‐doping was synthesized using the solid‐state route. The samples were characterized using X‐ray diffraction, dielectric analysis, and electromechanical measurements (piezoelectric d33 coefficient, coupling factor kp, mechanical quality factor Qm, and internal bias field Ebias). The increase in the ferroelectric‐relaxor transition temperature upon Zn‐doping was accompanied by a shift of the MPB toward the Na1/2Bi1/2TiO3‐rich side of the phase diagram. Higher tetragonal phase fraction and increased tetragonal distortion were noted for Zn‐doped (1 – x)Na1/2Bi1/2TiO3‐xBaTiO3. In addition, ferroelectric hardening and the presence of an internal bias field (Ebias) were observed for all doped compositions. The piezoelectric constant d33 and the coupling coefficient kp decreased by up to ∼30%, while a 4‐ to 6‐fold increase in Qm was observed for the doped compositions. Apart from establishing a structure–property correlation, these results highlight the chemically induced shift of the phase diagram upon doping, which is a crucial factor in material selection for optimal performance and commercialization. [ABSTRACT FROM AUTHOR]

The (1 – x)BiFeO3‐xPbTiO3 (BFO‐PTO) perovskite solid solution has great potential for being used in practical devices, as it exhibits significant ferroelectric response at its morphotropic phase boundary (MPB). However, the significant conduction, particularly high electrical leakage currents that BFO‐PTO films show at room temperature, deteriorates their functionality. This is mainly associated with the presence of multivalent iron along with A‐site and oxygen vacancies. Here, solution‐derived BFO‐PTO thin films have been crystallized at low temperature on Pt/TiO2/SiO2/Si substrates, by a rapid thermal annealing process to minimize Bi and Pb volatilization. X‐ray analyses have revealed that textured films are obtained with a pseudocubic perovskite structure and without the formation of detectable second phases. Microstructural studies indicated a columnar growth of the films with grain size well above the nanometric range, which, therefore, should not produce an appreciable reduction of the ferroelectric response due to size effects. Because of the relatively low content of charged defects produced in these BFO‐PTO films during processing, ferroelectric hysteresis loops can be measured at room temperature. The highest value of remnant polarizations (2PR = 58 μC/cm2) was obtained for the 0.65BiFeO3‐0.35PbTiO3 (65BFO‐35PTO) films, which suggests that this film composition lies in the proximity of the MPB where the coexistence of a highly textured <100> tetragonal phase and a rhombohedral one seems to occur. [ABSTRACT FROM AUTHOR]

To develop high‐performance piezo‐/ferroelectric materials, Bi(Zn½Ti½)O3–PbZrO3–PbTiO3 (BZT–PZ–PT) ternary solid solution with compositions around the morphotropic phase boundary (MPB) is synthesized by solid‐state reaction. The crystal structure and electric properties are investigated systematically by X‐ray powder diffraction (XRD), dielectric spectroscopy, and ferroelectric and piezoelectric measurements. On the basis of the results of the XRD, dielectric and ferroelectric measurements, the pseudo‐binary phase diagram of the yBi(Zn½Ti½)O3–(1 − y)[(1 − x)PbZrO3–xPbTiO3] system has been constructed for three series, namely, y = 0.05, 0.10, and 0.15. It is found that the introduction of BZT into the PZT system makes the paraelectric to ferroelectric phase transition more diffuse, brings the MPB to a lower PT content, and enlarges the MPB region. The best properties with an improved dielectric constant ε' = 1248, and a large remnant polarization Pr = 33 μC/cm2, as well as a relatively high TC = 286°C, and a high coercive field Ec = 23 kV/cm was achieved in the y = 0.15 series with MPB composition x = 0.425, making it a promising material for high‐power piezoelectric applications. [ABSTRACT FROM AUTHOR]

A series of morphotropic phase boundary (MPB) compositions of (1–x)Na1/2Bi1/2TiO3‐xBaTiO3 (x = 0.05, 0.055, 0.06, 0.065, 0.07), with and without 0.5 mol% Zn‐doping was synthesized using the solid‐state route. The samples were characterized using X‐ray diffraction, dielectric analysis, and electromechanical measurements (piezoelectric d33 coefficient, coupling factor kp, mechanical quality factor Qm, and internal bias field Ebias). The increase in the ferroelectric‐relaxor transition temperature upon Zn‐doping was accompanied by a shift of the MPB toward the Na1/2Bi1/2TiO3‐rich side of the phase diagram. Higher tetragonal phase fraction and increased tetragonal distortion were noted for Zn‐doped (1 – x)Na1/2Bi1/2TiO3‐xBaTiO3. In addition, ferroelectric hardening and the presence of an internal bias field (Ebias) were observed for all doped compositions. The piezoelectric constant d33 and the coupling coefficient kp decreased by up to ∼30%, while a 4‐ to 6‐fold increase in Qm was observed for the doped compositions. Apart from establishing a structure–property correlation, these results highlight the chemically induced shift of the phase diagram upon doping, which is a crucial factor in material selection for optimal performance and commercialization. [ABSTRACT FROM AUTHOR]

Lead‐based Pb(Zn1/3Nb2/3)O3‐Pb(Zr1/2Ti1/2)O3 (PZN‐PZT) piezoelectric ceramics have been intensively studied owing to their excellent performance in multilayer actuators; however, the detailed crystal structure and actuation mechanisms are still not well understood. In this study, in situ electric‐field‐biasing high‐energy synchrotron X‐ray diffraction was employed to monitor the crystal structure evolution and to deconvolute contributions to the electrostrain in the morphotropic phase boundary composition of 0.3PZN–0.7PZT. An electric‐field‐induced reversible phase transition between the coexisting monoclinic and tetragonal phases was identified. The unit cell parameters of the monoclinic phase exhibit significantly greater response to the electric field than those of the tetragonal phase. The effective lattice strain, evaluated through peak profile fitting, and the macroscopic strain measurement were found to be in agreement. The high electrostrain is primarily caused by the electric‐field‐induced phase transition with concurrent intrinsic/extrinsic contributions. This work provides a deeper description of the crystal structure and actuation mechanisms in PZN‐PZT piezoelectric systems. [ABSTRACT FROM AUTHOR]

Due to the feature of domains, ferroelectric materials display hysteresis behavior with respect to the change of the applied electric field. Every ferroelectric material has its own unique hysteresis loop reflecting the information of domain reversal under an electric field. In this work, the scaling behaviors of dynamic hysteresis in relaxor (1‐x)Pb(Mg1/3Nb2/3)O3‐xPbTiO3 (PMN‐PT) ceramics with different compositions were studied systemically. Our results showed that the evolution of scaling behavior in PMN‐PT ceramics can be divided into three stages, which is independent of the phase structure of the ceramics and the testing electric field frequency. The relationship between hysteresis area and field amplitude E0 obeys the power law ∝fαE0β in the low and high E0 regions, where the reorientations of 180° and non‐180° domain are dominant, respectively. However, the dynamic hysteresis area does not follow the power law in the intermediate E0 regions, which is attributed to the interaction of different domain reversal mechanisms. Furthermore, the hysteresis area decreases gradually with increasing frequency at a certain E0 and the time‐dependent domain reversal process was also discussed. [ABSTRACT FROM AUTHOR]

The phase transition and dielectric properties of Pb0.988(Hf0.945SnxTi0.03‐xNb0.025)O3 ceramics (0 ≤ x ≤ 0.03, correspondingly abbreviated as H1, H2, H3, and H4) at the morphotropic phase boundary were systematically investigated. X‐ray diffraction results and P‐E hysteresis loops show that the dominate orthorhombic antiferroelectric phase and a small amount of the tetragonal FE phase coexist in Pb0.988(Hf0.945SnxTi0.03‐xNb0.025)O3 ceramics. As the Sn content increases, the antiferroelectricity is significantly enhanced, accompanied with an increased Curie temperature and sharply reduced peak dielectric constant. H1 and H2 experience an irreversible field‐induced AFE‐FE phase transition at the ambient temperature, and the transition from a metastable FE phase to the original AFE phase is observed in H2 when heated to 60°C. H3 and H4 experience an invertible AFE‐FE phase transition, along with an enhanced forward phase switching field EF. Moreover a decreased backward phase switching field EA for H4 is detected as the electric field increases due to the AFE/FE coexistence. These results reveal the unique phase transition characteristics of AFE materials near the phase boundary, which is helpful for better understanding of AFE/FE materials. [ABSTRACT FROM AUTHOR]

This work demonstrates the critical role of orbital hybridizations in the FeO6 octahedral distortion, composition-driven phase transition, and bonding covalency in multiferroic (Bi1-xSmx)FeO3 (x = 0.10-0.20) ceramics in the vicinity of the morphotropic phase boundary (MPB). Sequential composition-driven transitions from the polar rhombohedral R3c to antipolar orthorhombic Pbam and then Pnma phases were revealed as the system crosses the MPB with increasing Sm. A coexistence of ferroelectric (FE) rhombohedral R3c and antiferroelectric (AFE) PbZrO3-like orthorhombic Pbam symmetries was identified by the 1/2{000}, 1/4 {100}, 1/4{110}, 1/4{111}, and 1/4{121} superlattice diffractions at x = 0.12-0.16. In addition to R3c and Pbam space groups, the nonpolar SmFeO3-like orthorhombic Pnma space group becomes the predominant phase at x = 0.20 confirmed by the 1/2{100} superlattice diffractions. The Fe L3-edge and oxygen Kedge synchrotron X-ray absorptions indicate that the O 2p-Fe 3d and O 2p-Bi 6s/6p orbital hybridizations were decreased as the system approaches the MPB. [ABSTRACT FROM AUTHOR]