Morphotropic Phase Boundary Research Articles

Significantly enhancing high-temperature piezoelectric response and Tdr of BF-BT-based ceramics through multi-component optimization strategy

Phase boundary-domain engineering modulation with diverse group elements and coexistence of multiphase and composite domain structures is a good pathway that can be realized to simultaneously improve the piezoelectric properties of BF-BT ceramics and their thermal stability. Here, we propose a multicomponent optimization strategy. We innovatively introduce the 0.8(Bi0.5Na0.5)TiO3-0.2(Bi0.5K0.5)TiO3 (BNT-20BKT) component to 0.69BF-0.31BT ceramic, to build a morphotropic phase boundary (MPB) for enhancing d33. Meanwhile, Bi(Zn0.5Ti0.5)O3 with high Curie temperature and high tetragonal degree was introduced with the expectation of obtaining higher thermal stability along with high piezoelectric properties. The 0.69BiFeO3-0.31BaTiO3-0.005[0.8(Bi0.5Na0.5)TiO3-0.2(Bi0.5K0.5)TiO3]-xBi(Zn0.5Ti0.5)O3 (referred to as BF31BT-0.005(BNT-20BKT)-xBZT, 0.00 ≤ x ≤ 0.025) ceramics were successfully prepared. For the first time, an ultra-high piezoelectric performance of 749.6 pC/N was achieved at a real-time depolarization temperature (Tdr) of 395.6 °C, reflecting the real-time piezoelectric properties and ultra-high temperature stability of the ceramic at high temperatures. A two-phase coexisting structure of R and PC phases was produced in BF31BT-0.005(BNT-20BKT)-0.025BZT ceramic. TEM results showed the formation of nanodomains and a large number of polar nanoregions (PNRs). By adjusting the appropriate R/PC phase ratio, oxygen octahedral distortion, and optimizing the local domain engineering, an effective strategy is provided for simultaneously achieving ultra-high temperature stability and ultra-high piezoelectric response.

Morphotropic phase boundary evolution with synergistic effect of sintering temperature to improve electrocaloric and energy storage performances of lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramic

The designing of lead-free ferroelectric ceramics for application in environment-friendly efficient electrocaloric cooling and energy storage devices is still challenging and need to be considered. A major challenge, however, is how to simultaneously achieve higher polarization and low hysteresis loss at low applied electric field. In this perspective, we comprehensively investigated sol-gel derived Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramics by varying the sintering temperature to explore its electrocaloric and energy storage capabilities. The excellent ∆T ∼ 1.03 K, ∆S ∼ 1.32 J/kg.K and high electrocaloric responsivity ΔT/ΔE ∼ 0.34 K.mm/kV at very low applied electric field of 30 kV/cm are obtained for pristine BCST sample sintered at 1400 °C. Additionally, we observed Wrec ∼ 136.18 mJ/cm3 and giant energy conversion efficiency η ∼ 94.29 % under very low applied electric field of 30 kV/cm for the same BCST sample. Our results reveal that control of sintering temperature contributes to a favorable and stable microstructure, including R-O-T phase coexistence and substitutional heterogeneity-induced nano-polar regions (PNRs) which strengthens the Polarization and supports the thin hysteresis loop. Thus all these factors simultaneously contributing to make BCST ceramic as a potential material for applications in advanced electrocaloric cooling and energy storage capacitors.

Evolution of magnetization of Bi1-ySmyFe1-xTixO3 ceramics at the morphotropic phase boundary attested by multistep magnetization measurements, time aging and electric field

Bi1-ySmyFe1-xTixO3 ceramics with compositions at the rhombohedral- orthorhombic morphotropic phase boundary (y = 0.1, 0.12, 0 ≤ x ≤ 0.1) were prepared by solid state reaction method. Analysis of the crystal structure of the compounds based on the results of laboratory and synchrotron X-ray diffraction measurements as well as Raman spectroscopy experiments revealed a coexistence of the rhombohedral phase (SG R3c) and the anti-polar orthorhombic phase (SG Pbam) in the compounds Bi0.88Sm0.12Fe1-xTixO3 with 0 ≤ x ≤ 0.1; the compounds Bi0.9Sm0.10Fe1-xTixO3 are characterized by the mixed structural state for the concentration range 0 ≤ x ≤ 0.06 and by the single phase rhombohedral state within 0.06 < x ≤ 0.1. Room temperature magnetization measurements demonstrate a gradual increase of remanent magnetization with Ti content in the compounds of both systems up to the maximal value of MR ∼0.28 emu/g for compounds with x = 0.06 which is followed by a decrease in magnetization with further titanium doping. Temperature decrease leads to a reduction of remanent magnetization which is mainly caused by a partial recovery of spatially modulated spin structure occurred in the compounds of both systems. Time aging of the compounds for about ∼1 year leads to a drastic increase of MR, which is caused by a change in the structural phase ratio, homogeneity of the structural state and a contribution of unbounded spins demonstrated by low field measurements. Subjecting of the annealed compounds to external electric field of E ∼40 kV/cm leads to a decrease of magnetization associated with backward structural transformations and redistribution of the local structural defects in the compounds.

The high-pressure structure of (1-x)Na0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{0.5}$$\\end{document}Bi0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{0.5}$$\\end{document}TiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}-xBaTiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document} at the morphotropic phase boundary

The pressure-induced structural changes in the perovskite-type (ABO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}) ferroelectric solid solution (1-x)Na0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{0.5}$$\\end{document}Bi0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{0.5}$$\\end{document}TiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}-xBaTiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document} (NBT-xBT) at the morphotropic phase boundary (MPB) (xMPB=0.048\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x_{\ ext {MPB}}=0.048$$\\end{document}) have been analyzed up to 12.3 GPa by single-crystal x-ray diffraction with synchrotron radiation. A pressure-induced phase transition takes place between 4.4 and 5.0 GPa, where the pseudocubic low-pressure phase transforms into an orthorhombic high-pressure phase with space group Pnma. The high-pressure phase is comprised of mixed BO6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_6$$\\end{document} tilts and anti-polar A-cation displacements, without exhibiting coherent off-centered shifts of the B-site Ti4+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{4+}$$\\end{document} cations that can be detected by synchrotron x-ray diffraction. Our results reveal that at ambient pressure and room temperature the NBT-xMPB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x_\\mathrm{{MPB}}$$\\end{document}BT structure possesses anti-phase BO6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_6$$\\end{document} tilts with a relatively large correlation length and the same type of polar distortions as those present in pure NBT, but with strongly violated correlation length due to Ba2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{2+}$$\\end{document}-induced local elastic-stress fields. For xMPB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x_{\ ext {MPB}}$$\\end{document} the effect of Ba on the mesoscopic-scale structure is compensated by a mild external pressure of only 0.7 GPa, resulting in structural features resembling those of pure NBT at ambient conditions.

Compositional ordering driven morphotropic phase boundary in ferroelectric solid solutions

Compositional ordering driven morphotropic phase boundary in ferroelectric solid solutions

Tracking high-performance Pb(Ni1/3Sb2/3)O3–Pb(Zr0.48Ti0.52)O3 piezoelectric ceramics near morphotropic phase boundary

Tracking high-performance Pb(Ni1/3Sb2/3)O3–Pb(Zr0.48Ti0.52)O3 piezoelectric ceramics near morphotropic phase boundary

Large ferroelectric polarization and high dielectric constant in HfO2-based thin films via Hf0.5Zr0.5O2/ZrO2 nanobilayer engineering

HfO2-based ferroelectric films have been extensively explored and utilized in the field of non-volatile memory and electrical programmability. However, the trade-off between ferroelectric polarization and dielectric constant in HfO2 has limited the overall performance improvement of devices in practical applications. Herein, a novel approach is proposed for the Hf0.5Zr0.5O2/ZrO2 (HZO/ZrO2) nanobilayer engineering, which can effectively regulate the phase structure evolution of HfO2 films to construct a suitable morphotropic phase boundary (MPB). The findings highlight that the top ZrO2 layer can regularly promote the formation of either the ferroelectric o-phase or the antiferroelectric t-phase. An ideal MPB is successfully established in HZO/ZrO2 (6/9 nm) nanobilayer film by carefully optimizing the HZO/ZrO2 thickness ratio, which presents a high dielectric constant of 52.7 and a large 2Pr value of up to 72.3 μC/cm2 without any wake-up operation. Moreover, the HZO/ZrO2 nanobilayer thin films demonstrate faster polarization switching speed (1.09 μs) and better fatigue performance (109 cycles) compared to the conventional HZO solid solution films. The relationship between ferroelectric and dielectric properties can be harmoniously balanced through the designation. The results indicate that the HZO/ZrO2 nanobilayer engineering strategy is quite potential to pave the way for the development of next-generation memory technologies with superior performance and reliability.

Giant Piezoelectric Effects of Topological Structures in Stretched Ferroelectric Membranes.

Freestanding ferroelectric oxide membranes emerge as a promising platform for exploring the interplay between topological polar ordering and dipolar interactions that are continuously tunable by strain. Our investigations combining density functional theory (DFT) and deep-learning-assisted molecular dynamics simulations demonstrate that DFT-predicted strain-driven morphotropic phase boundary involving monoclinic phases manifest as diverse domain structures at room temperatures, featuring continuous distributions of dipole orientations and mobile domain walls. Detailed analysis of dynamic structures reveals that the enhanced piezoelectric response observed in stretched PbTiO_{3} membranes results from small-angle rotations of dipoles at domain walls, distinct from conventional polarization rotation mechanism and adaptive phase theory inferred from static structures. We identify a ferroelectric topological structure, termed "dipole spiral," which exhibits a giant intrinsic piezoelectric response (>320 pC/N). This helical structure, possessing a rotational zero-energy mode, unlocks new possibilities for exploring chiral phonon dynamics and dipolar Dzyaloshinskii-Moriya-like interactions.

Optimization of energy storage and electrocaloric performance in Pb(Zr,Ti)O3 via A-Site La and Bi Co-doping

Lead-based ferroelectrics are one of the most fascinating candidates in the field of state-of-the-art electronic technology. Their intriguing properties are further enriched via the realization of morphotropic phase boundaries. Moreover, the A-site chemical substitution provides insight into the emergence of various exotic phases. Here, we employ co-doping of La3+ and Bi3+ at the A-site of Pb(Zr,Ti)O3 (PZT) ferroelectric to broaden the practical perspective of relaxor systems. Here, we emphasize that the A-site co-doping approach introduces technologically appealing amendments in the well-established temperature composition phase diagram of the PZT system. La3+ and Bi3+ doping favors the evolution of a novel response to thermal and field fluctuations. The maximum values of −ΔS are found to be ∼0.157, 0.118 and 0.176 J (kg·K)−1 for x=0.01, 0.02 and 0.03 , respectively. We employ the electrocaloric characteristics and Arrott plot as probing tools. The observation of a negative electrocaloric effect and the systematic reversal of Arrott lines, followed by a poling effect on the dielectric constant, reveals the emergence of ergodic phase as a novel phase. This further reveals that the Bi doping approach leads to the emergence of exotic characteristics in the chemically modified PZT system. The maximum observed recoverable energy for the composition for x = 0.01 is 0.0479 J cm−3 at a temperature of 388 K.

Exploring the Possibility of Thermally Assisted Creation and Annihilation of Anti‐Frenkel Defects in a Multiferroic Oxide for Tuning Interfacial Ferroelectricity

AbstractLattice defects such as oxygen vacancies, interstitials, and their complexes are present in crystalline oxide materials. In particular, anti‐Frenkel defects, which refer to charge‐neutral anion vacancy‐interstitial pairs, are strongly coupled with ferroelectric and dielectric properties as electric dipoles. However, in order to observe their macroscopic manifestation, delicate defect controls are required to the extent that electronic and ionic charges are almost completely suppressed. Here, the thermal cycle dependence of dielectric and piezoelectric properties is scrutinized in the strain‐driven morphotropic phase boundaries of multiferroic La‐substituted BiFeO3 thin films. Electrochemical impedance spectroscopy provides the Warburg feature that is considered evidence of the ionic origin. The observations are discussed based on anti‐Frenkel defects that are created or annihilated reversibly by thermal cycles through high‐temperature structural phase transition temperature or magnetic Néel temperature. The defect dipoles are spontaneously aligned by the flexoelectric effect in the phase boundaries inducing a metastable interfacial ferroelectric phase. The findings offer useful insight into defect dipoles.

Solid Solutions of Plastic/Ferroelectric Crystals: Toward Tailor-Made Functional Materials.

Plastic crystals that show ferroelectricity are highly promising materials for a wide range of applications. Their inherent remarkable malleability and highly symmetric cubic structures in the plastic crystal phase ensure that their ferroelectricity and related properties are retained in their bulk polycrystals. To develop functional materials based on such plastic/ferroelectric crystals, methods to tune their properties for specific applications are required. Here, we report the preparation of solid solutions of plastic/ferroelectric ionic crystals by mixing crystals with a common anion but different cations, or crystals with a common cation but different anions, which allows a continuous modification of the Curie temperature of the ferroelectric system over a range of 100 K. This adjustment of the Curie temperature allows the flexible tuning of the pyroelectric properties of the solid solutions, including a significant enhancement of room-temperature performance. The solid solutions also exhibit morphotropic phase boundaries in the composition-temperature phase diagrams, which shows an abrupt change in crystal structures with a variation of composition. This study showcases a simple and versatile property-tuning method that can be expected to pave the way for major progress in the development of materials based on plastic/ferroelectric crystals, which will eventually advance to the stage of pursuing tailor-made functional materials with desired properties.

Quaternary piezoelectric ceramics with ultra-high mechanical quality factor

The development of piezoelectric ceramics with large piezoelectric coefficient (d33), high Curie temperature (TC) and high mechanical quality factor (Qm) is still a key challenge for practical application for high-power device. Herein, a novel quaternary piezoelectric ceramics of (0.125-x) Pb0.98Sr0.02(Mg1/3Nb2/3)O3–0.445PbTiO3–0.43PbZrO3-xPb(Mn1/3Nb2/3)O3 (abbreviated as xPMnN-PSMN-PZT) were prepared by the solid-state sintering method. The hard dopant PMnN induced the morphotropic phase boundary (MPB) of PSMN-PZT into a tetragonal-rich region. In addition, the XPS and EPR analysis proved the existence of a large amount of oxygen vacancies (Vo••) in PMnN-PSMN-PZT ceramic system. The composition near tetragonal-rich MPB region and the appearance of defect dipoles formed a strong coupling effect on the domain wall motion and leaded to an ultra Qm value. The optimum piezoelectric properties were achieved at x = 9 mol% with d33 = 260 pC/N, Qm = 3880, tanδ = 0.009 and TC = 332 °C. A significant internal bias field (Ebias) of 8.83 kV/cm was also observed in 0.09PMnN-PSMN-PZT ceramics. The origin of this excellent piezoelectric properties was explained by the phase structure, piezoelectric and dielectric analysis. This work demonstrated a rational strategy to obtain ultra Qm value for high-power piezoceramics.

Giant overall energy density performances via introducing aliovalent cations in BNT-based ferroelectric ceramics

The strategy of introducing aliovalent cations in the ferroelectric perovskites is the most promising for obtaining excellent overall energy storage density performances, simultaneously with good efficiency and thermal stability in dielectric ceramics for high pulse power technologies. Aliovalent cations could greatly enhance the short-range ferroelectric order (Polar nanoregions, PNRs), and local random field caused by vacancies, mismatch between size, electronic configuration, and other physical and chemical properties of aliovalent cations with the host perovskite. PNRs and local random field make the ceramic relaxor like with excellent overall energy storage density results such as total energy storage density (WT = 10.55 J/cm3, recoverable energy storage density Wrec = 7.82 J/cm3), power density (PD = 197 MW/cm3), current density (CD = 1312 A/cm2), and ultra-fast discharge rate (t = 24 ns) simultaneously with good working efficiency of 74 % by introducing 14 mol% of Bi(Zn1/3Nb2/3) aliovalent cations in the morphotropic phase boundary (MPB) (Bi0.47Na0.47)TiO3–0.06BaTiO3 composition. In addition, the same optimum sample also showed good thermal stability up to 240 °C, with <10–13 % variation in recoverable energy storage density and working efficiency respectively. The reason of excellent overall energy storage density, and their thermal stability in a broad temperature range might be due to short-range ferroelectric order, local random field, relaxor ferroelectric polymorphic phases, highly dense microstructure with small and uniform grains, as well as large band gape. Our study provides a good clue to obtain giant overall energy density results with good working efficiency and thermal stability in relaxor ferroelectric ceramics for high pulse power technology.

Establishing the morphotropic phase boundary in van der Waals ferroelectrics

The formation of morphotropic phase boundaries (MPBs) is a pivotal strategy in piezoelectric ceramics and crystals, primarily used to enhance the electromechanical coupling. However, the application of this strategy in van der Waals (vdW) piezoelectrics and ferroelectrics has been limited, largely due to challenges in achieving phase coexistence and enabling possible polarization rotation. In this study, we address this gap by synthesizing a Selenium doped vdW ferroelectric, CuInP2(S1−x Se x )6, with a doping range of 0 ⩽ x⩽ 0.15, to create an MPB. Our findings indicate the presence of an MPB near x = 0.05, situated between monoclinic and trigonal phases. This boundary was confirmed using x-ray diffraction and transmission electron microscope techniques. Remarkably, the composition at x = 0.05 shows a high dielectric constant (ϵr = 13.8) and an impressive local effective piezoelectric coefficient (d 33eff = 51 pm V−1) at 80 K. Additionally, an unusual softening of the Young’s modulus was observed near MPB. These results are crucial for enhancing electromechanical coupling in vdW layered materials and herald new avenues for the design and optimization of piezoelectric and electromechanical properties in these materials.

Influence of Lithium on Structural Properties of Lead Zirconium Titanate (PZT)

Lead Zirconium Titanate (PZT) is a potential piezoelectric material for sensor and transducer applications due to its outstanding piezoelectric coupling near the morphotropic phase boundary (MPB). This is because PZT can switch between tetragonal and rhombohedral phases. PZT is still considered to be one of the piezoelectric materials that has received the greatest amount of attention from researchers and is used the most frequently. Modification with Lithium will improve the piezoelectric properties. In this study, the structural properties and morphological studies of Lead zirconium titanate and Lead zirconium titanate with Lithium modification have been evaluated. Various Scherrer’s models and other models, such as the Williamson-Hall model and Size-strain plots model, were used to display the observed fluctuations in crystallite size. Morphological analysis was used to determine the particle size. Graphs showing the distribution of particle sizes were drawn.

Morphotropic phase boundary composition PNN-PZT ceramics and their outstanding electromechanical properties

xPb(Ni1/3Nb2/3)O3-(1-x)Pb(Zr,Ti)O3 (x = 0.12, 0.24, 0.36, 0.42, 0.55 and 0.64) ceramics were prepared using conventional solid-state reaction. The morphotropic phase boundary (MPB) composition region, sintering characteristics and performance parameters of ceramic samples with different PNN compositions were studied. The phase structure, microstructure and electrical properties were characterized in detail. The results show that the Curie temperature (TC) of PNN-PZT ceramics decreases from 324 °C to 44 °C while the piezoelectric coefficient (d33) changes from 43 pC/N to 1170 pC/N with PNN content from 0.12 to 0.64. Interesting phenomena were observed, which can provide useful information for practical applications of PNN-PZT ceramics.

Multifunctional Experimental Studies of Sm-Ion-Influenced Pseudo-Cubic Morphotropic Phase Boundary Regional BiFeO3-xSrTiO3 Ceramics for High-Temperature Applications

In this manuscript, for the first time, the exploration of the microstructural, ferroelectric, piezoelectric, and dielectric performances are measured for Sm-ion-influenced pseudo-cubic, morphotropic phase boundary (MPB) regional 0.62BiFeO3−0.38SrTiO3:xwt%Sm2O3 (BFST:xSm) ceramics with x = 0–0.25. All the compositions maintained their pseudo-cubic MPB structural stability. The composition of BFST:0.15Sm ceramics exhibited an excellent remnant polarization (Pr) of ~52.11 μC/cm2, an enhanced d33 of 101 pC/N, and the highest relative dielectric constant (ɛr) of ~1152, which are much improved as compared to that of pure BFST ceramics. BFST:0.15Sm ceramics demonstrated a Curie temperature (TC) of 378 °C. Moreover, the composition exhibited high thermal stability for d33 72 pC/N (only a 28% decrease), even at a high temperature of 300 °C. Such outstanding outcomes make BFST:0.15Sm ceramics an ideal applicant for high-temperature piezoelectric applications.

An Emergent Quadruple Phase Ensemble in Doped Bismuth Ferrite Thin Films Through Site and Strain Engineering

AbstractIn ferroic materials, giant susceptibilities can be realized at artificially constructed phase boundaries through deterministic manipulation of the order parameter. Here, emergent ferroelectric structural phase evolution behavior is demonstrated through a synergistic combination of A‐site doping and strain engineering. Using chemical solution deposition derived (001)‐oriented Sm‐substituted bismuth ferrite (Bi1‐xSmxFeO3) films as a prototypical system, a morphotropic phase boundary comprising a coexistence of four distinct crystallographic phases is uncovered. These ferroelectric, polar, and nonpolar phases form a nanoscale mixture without the presence of crystallographically hard boundaries. The system thus possesses the ability to show both polarization rotation and extension, effectively releasing the polarization from its crystallographic constraint. Consequently, both robust ferroelectric properties and giant electromechanical responses are obtained. For instance, the optimized composition with x = 0.14 has a remnant polarization of 2Pr = 103 µC cm−2 and electromechanical response 175% that of undoped BFO. These findings showcase the tremendous potential of synthetic phase boundaries, particularly in the context of lead‐free functional multiferroics.

Doping effects and role conversion of CeO2 in 0.3PZN–0.7PZT ternary piezoelectric ceramics with enhanced electrical properties

In this work, the rare-earth doped ternary lead zirconate titanate ceramics with chemical formula of [0.3Pb(Zn1/3Nb2/3)O3–0.7Pb(Zr0.52Ti0.48)O3] + x wt% CeO2 (x=0–0.5, abbreviated as 0.3PZN–0.7PZT–xCe) were synthesized by a conventional solid-state reaction route, specific attentions was focused on the effects of CeO2 dopants on the structures and electrical properties of the 0.3PZN–0.7PZT ceramics, revealing the role conversion of CeO2 dopants with its doping amount (x). When less CeO2 (x≤0.2) is introduced into 0.3PZN–0.7PZT, the prepared ceramics are identified as the coexistence of rhombohedral and tetragonal phases, also involved with an increased grain size and a reduced atomic ratio of Pb/(Zr+Ti+Zn+Nb). The increased remanent polarization (Pr) and deceased coercive filed (Ec), as well as improved dielectric permittivity (εr) and piezoelectric coefficient (d33) demonstrate the donor substitution of Ce3+ for Pb2+ at the A-site of perovskite lattice. Conversely, the introduction of excessive CeO2 (x>0.2) causes a reversal evolution in the electrical properties of ceramics, suggesting that some of the introduced cerium element tends to become Ce4+, which equivalently substitutes for Zr4+ at the B-site. Additionally, the diffused phase transition (DPT) behaviors of the 0.3PZN–0.7PZT–xCe ceramics were investigated by the modified Curie–Weiss Law. The sample with x=0.2 shows reduced DPT character and optimized electrical properties, including TC=297 °C, εr=1400, d33=480 pC/N, tanδ=1.6%, kp=65%, d33×g33=16.32×10–12 m2/N, Pr=38.3 μC/cm2 and Ec=1.02 kV/mm. These enhanced electrical properties not only are contributed by the donor substitution effect of Ce3+, but also benefit from the optimized morphotropic phase boundary that is close to the tetragonal-rich side.

Synergistic design strategy for enhancing the piezoelectric performance of BiFeO3-Based high-temperature piezoelectric ceramics

A novel synergistic strategy was used to improve the piezoelectric characteristics of high-temperature piezoelectric ceramics. This work combined three commonly used strategies, constructing the Morphotropic Phase Boundary to reduce energy barriers, changing domain structures impacting macroscopic piezoelectric properties, and adjusting BO6 octahedral distortions reflecting microstructural changes, thus effectively regulating the piezoelectric behaviors of BiFeO3-based ceramics. As a result, the 0.67BiFeO3-0.32BaTiO3-0.01BiAlO3 component, exhibiting the maximum distortion of the BO6 octahedron and the coexistence of macrodomains and nanodomains, achieved the optimal piezoelectric characteristics (d33 = 225 ± 10 pC N−1, TC = 450 °C). Additionally, the ceramic maintained its high piezoelectric properties even at temperatures as high as 280 °C (346 pC N−1). This study presents a novel collaborative design strategy that combines phase structure, domain structure, and BO6 octahedral distortion, significantly enhancing the development potential of lead-free high-temperature piezoelectric materials in the future.