Morphotropic Phase Boundary Research Articles

Features of the magnetization in ceramics Bi0.86Sm0.14Fe1-xMnxO3 in the rhombohedral - orthorhombic morphotropic phase boundary

Crystal structure of the ceramic compounds Bi0.86Sm0.14Fe1-xMnxO3 prepared by solid state reaction method was studied using X-ray diffraction, scanning electron microscopy and Raman spectroscopy; magnetometry measurements were performed to study magnetic properties and to investigate a correlation between the magnetic and crystal structures of the compounds. The compounds with 0 = x ≤ 0.1 are characterized by the coexistence of the polar rhombohedral and the antipolar orthorhombic phases, an increase of Mn doping causes a stabilization of the orthorhombic phase. Room temperature magnetization data show a gradual reduction of the remanent magnetization with an increase of Mn concentration, while a decrease of temperature causes a nontrivial reduction of remanent magnetization which is determined by a transformation of the non-collinear antiferromagnetic structure towards the collinear antiferromagnetic structure. The magnetic state of the compounds notably depends on the phase ratio of the coexisting structural phases and consists of the antiferromagnetic phases associated with the respective rhombohedral and the orthorhombic phases as well as the ferromagnetic component associated with the phase boundary spins. An evolution of the mentioned magnetic subsystems is discussed as a function of the chemical composition and temperature.

Effect of MgO doping on energy storage and electrocaloric properties of ferroelectric 0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3 ceramics

This study highlights the effect of MgO doping on microstructure, dielectric, ferroelectric, energy storage and electrocaloric properties of lead-free (1-x)(0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3)–xMgO ceramics with x varying from 0-5%. X-ray diffraction studies revealed that BZCT-MgO ceramics exhibited a morphotropic phase boundary (MPB), i.e. coexistence of both tetragonal and rhombohedral phases at room temperature for x ≤ 1%. Scanning electron microscope (SEM) images revealed that grain size is decreased with the increase of MgO content. The Raman analysis and temperature dependent dielectric studies further confirm the MPB behaviour at low MgO content. Besides, the MgO additive improves the diffused phase transition (DPT) behaviour of BZCT ceramics, lowers transition temperature and enhances their relaxor behaviour. It is observed that 0.99BZCT–0.01MgO showed optimum energy storage properties with a recoverable energy density of 177.6 mJ/cm3 and an efficiency of 79% at an electric field of 45 kV/cm. Moreover, they exhibited a robust energy storage performance even after passing 107 cycles. Further, the electrocaloric temperature change and responsivity are found 1.12 K at 45 kV/cm and 0.024 Kcm/kV, respectively in 0.99BZCT–0.01MgO ceramics.

Enhancement of Piezoelectricity by Novel Poling Method of the Rare‐Earth Modified BiFeO3–BaTiO3 Lead‐Free Ceramics

AbstractIn piezoceramics, the Curie temperature (TC) and piezoelectric coefficient (d33) are often inversely proportional, so it is very difficult to optimize high piezoelectricity and TC simultaneously. In addition, the high and temperature‐insensitive piezoelectric strain coefficient (d33*) with small hysteresis is also a longstanding obstacle in the development of lead‐free ceramics. In this work, a facile approach of donor doping strategy is adopted to replace Ba2+ with Yb3+, Y3+, Sm3+, and Nd3+ as a result, a high TC of 450 °C and outstanding d33 of 422–436 pC N−1 is achieved by a novel magnetic poling method. Thermally‐stable and outstanding piezoelectric strain performance (d33* ≈ 520–550 pm V−1 and ΔST ≈ 10%) with small strain hysteresis (H < 20%) results are highly encourageable in lead‐free ceramics. The main factors contributing to high piezoelectricity are the morphotropic phase boundary, suppression of defect charges by donor doping, thermal quenching, mesoscale nanodomain size, and novel poling method. The excellent piezoelectric performance and high TC of this work are superior to those of state‐of‐the‐art piezoceramics. The synergistic approaches of compositional design strategy and novel poling process in this work are highly beneficial for temperature‐insensitive piezoelectric sensor and actuator applications.

The Specification of Dielectric Ternary Compound BNT-BKT-BT

The ternary ceramic compound (BNT-BKT-BT), like 0.855(Bi0.5Na0.5TiO3) 0.115(Bi0.5K0.5TiO3)-0.03(BaTiO3) was prepared by solid-state reaction. Three different calcination processes as a function of temperature and time had been used as the candidate for the structural phase. The crystal structure analysis confirmed a rhombohedral and tetragonal phase regarding diffracted peaks within the morphotropic phase boundary (MPB). The dielectric behavior at different frequencies (1, 10, 100 kHz, and 3 MHz) and temperatures showed a maximum curie temperature at (295 C) through a frequency (100 kHz). The XRD analyses showed the peak splitting observed around (2=40, and 46) related to the overlapping between many peaks mentioned by different phases. The appearance of the relaxer ferroelectric behavior emphasizes the agreement of the XRD analysis and dielectric measurement

Synergistic approach for enhancement of piezoelectricity in the lead-free BiFeO3-BaTiO3 ceramics

Large piezoelectric actuator coefficient (d33*) and enhanced piezoelectric sensor coefficient (d33) with high Curie temperature (TC) are desired for real applications. In this work, a synergistic approach of bipolar cycling and donor doping strategy was applied for the enhancement of piezoelectric performance. An excellent d33 value of 382 pC/N was achieved by the novel (AC-bias and DC-bias) poling method in the lead-free Nb-modified 0.67Bi1.03FeO3-0.33BaTiO3 quenched ceramics. In addition, a large d33* of ∼ 400 pm/V has been obtained under a very low electric field of 25 kV/cm along with a high TC ≈ 473 °C. This enhanced piezoelectric performance is related to the crystal structure morphotropic phase boundary, bipolar cycling, optimum grain size (∼5 µm), maximum lattice distortion, and soft-ferroelectric effect induced by the donor doping. The small strain hysteresis, Hs ≈ 20%, and temperature-insensitive piezoelectric strain, Δd33*(T) = d33*(T)/d33*(RT) ≈ 24% suggest the accurate and precise positioning in the piezoelectric actuator devices. The simultaneously improved d33 and temperature-stable d33* with a high TC are promising results in the lead-free BFBT ceramics.

Realizing an Ultrahigh Depolarization Temperature near the Curie Point and Large d33 with Superior Temperature Stability in Lead-Free Ceramics via a Sandwich Structure Design

An imminent challenge of lead-free Bi0.5Na0.5TiO3-based (BNT) piezoceramics is that the giant piezoelectric constant (d33) caused by the morphotropic phase boundary is incompatible with a high depolarization temperature (Td) and ultralow temperature coefficient (Ttc) of the real-time d33, which severely hinders their industrial application in the field of elevated temperatures. Herein, a sandwich-structured 0.94Bi0.5Na0.5TiO3-0.06BaTiO3/0.89Bi0.5Na0.5TiO3-0.11BaTiO3/0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (SWS-6/11/6BT-y, where y refers to the weight fraction of the BNT-11BT solid solution) ceramic composite is engineered for mitigating the conflict between d33, Td and Ttc. Following this strategy, ultrahigh Td near the Curie point (225 °C, close to that of the BNT-11BT layer) and relatively large d33 (130 pC/N, close to that of the BNT-6BT layer) are simultaneously realized in a SWS-6/11/6BT-40%-Q ceramic composite. More importantly, the ultralow Ttc (0.07%) of real-time d33 is also achieved in this work. The structural heterogeneity yields the high piezoresponse, and the built-in field resulting from layer-type ceramic composites provides the driving force to promote the diffused ferroelectric-relaxor phase transition and the resultant ferroelectric order with high Td. The above synergistic contributions realize the remission of the d33-Td-Ttc conflict in a sandwich-structural SWS-6/11/6BT-40% ceramic composite. Thus, our work provided a path for designing the BNT-based piezoceramics with potential for industrial applications.

Preparation of Phase-Pure Perovskite 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 Ceramics and Effects of Perovskite Phase Purity

0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNT) piezoelectric ceramics were prepared by traditional ceramic processing via B-site oxide mixing route and columbite precursor method using oxides as raw materials, where the influences of MgO purity, whether heat treatment of MgO and synthesis techniques were studied. When using MgO with purity of 98%, the amount of pyrochlore phase in the sintered PMNT ceramics is rather high no matter what synthesis techniques used. Phase-pure perovskite PMNT ceramics can be prepared via the columbite precursor method using 99.99% MgO as raw material after pre-heated at 1200 °C for 4 h. All the PMNT ceramics exhibit rhombohedral perovskite structure with composition approaching the morphotropic phase boundary. The ceramics’ density is affected little by pyrochlore impurity, whereas the sintering temperature range is narrow and the 1245 °C sintered phase-pure PMNT ceramics have the largest relative density and compact micro-morphology. The PMNT ceramics present apparent relaxor ferroelectrics characteristic, where the samples with low content of pyrochlore phase or with phase-pure perovskite structure have excellent dielectric property. The samples present easy polarization characteristic, in which the PMNT ceramics with high purity or phase-pure perovskite phase have excellent piezoelectricity.

Structural, dielectric and piezoelectric characterization of BFN-modified PZT-based (MPB) ceramics

ABSTRACT The solid solution of xBi(Fe1/3Nb2/3)O3–(1-x)Pb(Zr0.50Ti0.50)O3 ceramics near morphotropic phase boundary (MPB) (BFN–PZT, x = 0, 0.0025, 0.005, 0.0075, 0.01) were prepared by conventional solid-state reaction method. The samples added with different Bi2O3, Fe2O3, Nb2O5 contents were compared in terms of the phase structure, microstructure, dielectric properties, and piezoelectric properties. In particular, rhombohedral-tetragonal morphotropic phase boundary was observed in BFN–PZT crystal structure near the composition of x = 0.005. The BFN–PZT ceramics exhibited the following optimal properties at x = 0.005: dielectric constant ϵr of 847, dielectric loss tanδ of 0.034, Curie temperature TC of 390°C, electrical conductivity σ of 0.441 (Mohm.m)−1, piezoelectric charge constant d33 of 416 pC/N, electromechanical coupling factor KP of 0.654, and mechanical quality factor Qm of 426, making it a promising material for use in high-intensity ultrasound applications.

Study structural, dielectric and ferroelectric properties of Pb (Zr1-x Tix)O3 ceramics near the morphotropic phase boundary

In the present work, Pb(Zr(1-x)Tix) ceramics (x = 0.50, 0.48, 0.45 and 0.42) were prepared using the solid state reaction method, at the sintaring temperature (1100 oC ) for (6hr).X-ray diffraction results demonstrate that all the samples lie within the morphtropic phase boundary (MPB) region in the pure perovskite tetragonal structure with Miller transactions (100), (110), (111), (200), (210), (211), (220), (103) and (311) that the prevailing trend is (110) and the results of plasticity microwave very close sense of distance intra-convergent also relatively few crystalline defects. Increasing the bulk density of the true density of altered concentration of zirconium and titanium. Results of the examination microscope also showed that the particle size (Dnm) be tight between the samples and the homogeneity of the granules, as well as increasing the homogeneity of compositional structure, causing an improvement in the structural and electrical properties. Shown technique results EDAX compound of the interacting elements of the composition and there is little difference between the real weight and the weight is noticeable. The temperature and concentration of titanium dependences of the dielectric constant of the ceramics has been investigated in detail. Excellent dielectric properties have been obtained for the selected compositions. Polarization-Elctric field hysteresis studies were carried out for all compositions at room temperature. It was found that with the increase of concentration of titanium content in the composition the remnant polarization decreases and ferroelectric loops get constricted.

Achieving giant electrostrain of above 1% in (Bi,Na)TiO3-based lead-free piezoelectrics via introducing oxygen-defect composition.

Piezoelectric ceramics have been extensively used in actuators, where the magnitude of electrostrain is key indicator for large-stroke actuation applications. Here, we propose an innovative strategy based on defect chemistry to form a defect-engineered morphotropic phase boundary and achieve a giant strain of 1.12% in lead-free Bi0.5Na0.5TiO3 (BNT)-based ceramics. The incorporation of the hypothetical perovskite BaAlO2.5 with nominal oxygen defect into BNT will form strongly polarized directional defect dipoles, leading to a strong pinning effect after aging. The large asymmetrical strain is mainly attributed to two factors: The defect dipoles along crystallographic [001] direction destroy the long-range ordering of the ferroelectric and activate a reversible phase transition while promoting polarization rotation when the dipoles are aligned along the applied electric field. Our results not only demonstrate the potential application of BNT-based materials in low-frequency, large-stroke actuators but also provide a general methodology to achieve large strain.

Synthesis and Characterization of a New Ferroelectric with Low Lead Content, a High Curie Temperature, and a High Piezoelectric Response

AbstractA new solid solution (1−x)Bi(Fe2/8Ti3/8Mg3/8)O3–(x)PbTiO3 (BFTM‐PT) is synthesized and the electromechanical properties are measured. This system is defined as a low‐lead material with ferroelectric/piezoelectric behavior and a morphotropic phase boundary (MPB) that leads to enhanced properties. The MPB is located between x = 0.30 and 0.35 and coincides with a structural phase transition and a sharp increase in the piezoelectric response. The system demonstrates ferroelectric hysteresis where x = 0.325 displays the best properties with a maximum polarization of 39 µC cm−2 and a remnant polarization of 26 µC cm−2. The range of compositions has high Curie temperature (Tc), ranging from 625–650 °C. Materials with a Tc above 400 °C typically have a low d33 of <50 pC N−1 at room temperature. However, BFTM‐PT has a higher d33 that most other compositions with a Tc in this range, with the highest being 145 pC N−1 for x = 0.375. The d33 drops off above 100 °C, but doping studies can be done in the future to stabilize the piezoelectric response at higher temperatures. These outstanding properties open the possibility of new transducer applications, in particular ones requiring high temperature and high power.

Synergy of lead vacancies and morphotropic phase boundary to promote high piezoelectricity and temperature stability of PBZTN ceramics

• A synergetic strategy including introducing lead vacancies by niobium doping and constructing an morphotropic phase boundary (MPB) was designed to improve the piezoelectricity and temperature stability. • Excellent piezoelectric properties ( d 33 =864 pC/N, k p =84%, T C =201 °C) and high temperature stability (less than 10% variations for electrical properties from 20 °C to 160 °C) are obtained simultaneously in PBZTN-0.540 ceramics. The flourishing development of emerging electromechanical applications has stimulated an urgent demand for ferroelectric ceramics with high piezoelectric properties and broad temperature usage range. However, it remains a challenge to simultaneously obtain good piezoelectricity and reliable temperature stability in lead zirconate titanate (PZT)-based piezoelectric ceramics. To solve this issue, a synergetic strategy was proposed to introduce lead vacancies through niobium doping and construct morphotropic phase boundary (MPB). In this work, Pb 0.905 Ba 0.085 (V Pb″ ) 0.01 [(Zr x Ti 1 -x ) 0.98 Nb 0.02 ]O 3 (PBZTN- x ) material system was designed. Good comprehensive properties ( d 33 = 864 pC/N, k p = 84%, T C = 201°C) and excellent temperature stability (less than 10% variation of electrical properties from 20°C to 160°C) were obtained in PBZTN-0.540 ceramics. Good piezoelectricity can be attributed to high extrinsic contribution (domain wall motion) induced by Pb 2+ vacancies and the existence of nano-domains emerged at MPB, while excellent temperature stability is mainly attributed to the minimized local stress in the lattice and the stable domain structure.

Features of coexistence of tetragonal and orthorhombic phases in lead-free ferroelectric solid solutions

A model of a heterophase sample with interlayers is proposed to describe coexistence of tetragonal and orthorhombic phases in lead-free perovskite-type ferroelectric solid solutions. Versions of phase coexistence are analyzed at variations of unit-cell parameters of (Ba, Ca)(Ti, Zr)[Formula: see text] and (K, Na)(Nb, Sb)[Formula: see text]-(Ba, Ca)[Formula: see text] with compositions near morphotropic phase boundaries. Large regions of the tetragonal and orthorhombic phases are split into [Formula: see text] and [Formula: see text] domains, respectively. The interlayer of the orthorhombic phase is either single-domain or split into [Formula: see text] domains. A complete stress relief can be achieved at an elastic matching of the polydomain/single-domain or polydomain/polydomain phases. It is shown that different phase contents in ([Formula: see text])[Formula: see text]([Formula: see text])[Formula: see text] powder and ceramic are caused by different non-[Formula: see text] domain structures in the phases. The interlayer of the orthorhombic phase plays an important role in forming the phase content in solid solutions. Agreement is shown when comparing the evaluated volume fractions of the orthorhombic phase to experimental data.

Growth and characterization of sodium potassium niobate single crystals near morphotropic phase boundaries

By using a high-temperature solution approach, lead-free single crystals of sodium potassium niobate Kx Na(1-x)NbO3 have been grown at three different phase boundary compositions (x = 0.17, 0.35, and 0.50). The monoclinic and orthorhombic crystal structures are present in the compositions × = 0.17 and × = 0.50 related crystal structures. Ferroelectricity is induced at lower temperatures and requires a smaller critical electric field when KNbO3 content is included into NaNbO3 crystals. Studies using the scanning electron microscope (SEM) and atomic force microscope (AFM) have shown how the sodium potassium niobate (KNN) crystals grow morphologically. With an increase in potassium concentration in the KNN system, the average step size falls. KNN crystals were subjected to impedance analyzer-based dielectric investigations. With an increase in concentration, a decrease in dielectric loss was found. The compositions with potassium concentrations of x = 0.50, 0.35, and 0.17 were found to have piezoelectric coefficients (d33) of 72 pC/N, 63 pC/N, and 52 pC/N, respectively.

Grain to grain heterogeneity in PZT thin films as probed by in situ biasing XRD

Piezoelectric thin films are particularly difficult to model at the grain scale. Moreover, this problem is sparsely experimentally documented due to the lack of adequate methods. Here, an original methodology is proposed to study the behavior of single grains during in situ biasing. Pb(Zr,Ti)O3 films have been evaluated thanks to an in situ biasing x-ray diffraction technique performed on a synchrotron source with a sub-micronic x-ray beam. Small capacitors have been biased with DC voltage between 0 and ±20 V and at each step of bias a set of spotty Debye rings have been recorded. By selecting an appropriate region of interest, the evolution of a single grain peak has been followed. The fine analysis of these peaks allows to calculate the effective piezoelectric coefficient d33,eff, the proportion of each domain variants, the tetragonality inside each grain, as well as their evolution during the electrical biasing. A higher heterogeneity in samples with morphotropic phase boundary composition is observed. This study contributes to a better understanding of the local behaviors in piezo/ferroelectric polycrystalline films and in the improvement of their performance for different applications.

Electric field-induced irreversible phase transformations in Pb(Zr, Ti)O3-based piezoceramics

La-modified Pb(Zr,Ti)O3 (PLZT) (d33 ∼ 650 pC/N) and unmodified Pb(Zr1-x, Tix)O3 in the composition range (0.35 = x ≤ 0.51) were electrically poled through a novel powder poling technique. The mechanisms of large piezoelectric response in morphotropic phase boundary (MPB) and non-MPB-based compositions were discussed. Structural analysis suggests MPB-based compositions undergo irreversible structural phase transformation and lattice distortion after poling, and non-MPB undergo irreversible structural phase transformation. In the framework of theories, it has been argued that the MPB compositions satisfy the polarization rotation cum structural distortion phenomenon and non-MPB-based compositions follow the polarization rotation model.

Effect of local compositional heterogeneity on the piezoelectric property at ferroelectric morphotropic phase boundary – A phase field study

In this work, the effect of local compositional heterogeneity on the domain structure and piezoelectricity at ferroelectric morphotropic phase boundary (MPB) is studied by phase field simulations. It is found that the local compositional heterogeneity leads to a unique domain structure at MPB, i.e., a mixture of tetragonal, monoclinic and rhombohedral domains. Although polarization rotation occurs for both MPB samples with and without local compositional heterogeneity, the piezoelectric d33 coefficient becomes reduced for the sample with local compositional heterogeneity because polarization rotation becomes more difficult on average. This work unravels the effect of local compositional heterogeneity on the piezoelectric property of ferroelectric MPB.

Field dependent energy density and induced relaxor ferroelectric to relaxor antiferroelectric property investigation in potassium modified NKBT – ST ceramics

Lead free 0.60 (Na0.5-xKxBi0.5TiO3) – 0.40 (SrTiO3) perovskite ferroelectric ceramics were synthesized effectively by a conventional solid-state reaction root. X – ray diffraction and Rietveld refinement revealed the co-existence of dual phase crystal symmetries for the ceramics around the morphotropic phase boundary in all samples. The coexistence of rhombohedral (R3c) and cubic (Pm3m) phases occurred up to the dopant concentration x = 0.07, succeeding a tetragonal (P4bm) with cubic (Pm3m) symmetries were observed for higher dopant concentrations x = 0.12 and 0.15 respectively. SEM micrographs indicate that the formation of well packed dense microstructure with the nonuniform distribution. Temperature dependent dielectric measurement provoke the dielectric relaxation at low temperature near at depolarization temperature (Td). And then, the incorporation of ST in NKBT host matrix triggers the shifting of Curie temperature (Tm) towards the low temperatures. A stable relaxor ferroelectric like behavior up to the dopant concentration x = 0.07, and antiferroelectric like relaxor behavior was triggered progressively up to x = 0.15 was observed through in P-E loop studies. The electric field dependent recoverable energy storage performance at room temperature was calculated and a significant energy storage density (Wrec) and energy storage efficiency (η) values noticed for x = 0.15 ceramic, which shows the x = 0.15 ceramic optimistic for energy storage applications in dielectric capacitors.

Enhanced electric field control of magnetism in ternary BiFeO3-based ceramics

We report an unambiguous observation of a room temperature (RT) converse magnetoelectric effect (CME) in ternary BiFeO3-based systems near a morphotropic phase boundary (MPB). The results of in situ XRD diffraction at different applied electric fields reveal that the lattice distortion and phase transitions dominate the RT CME in the samples near the MPB. Our results provide an experimental proof and an explanation for the electric-field control of the magnetism effect obtained at the MPB, which may provide an effective way to design multiferroics for potential applications in magnetoelectric devices with low power consumption.

Exotic role of poling protocol on augmentation of magnetoelectricity in BCZT/CNZF layered composites

Here, we report exotic role of electrical poling of layered BCZT-CNZF bulk composite for a sustainable advancement of magnetoelectric (ME) technology. Practically, it seems quite difficult to access full potential of ME composites due to their weak ME coupling performances. Using a standard poling protocols, we successfully deployed coupling performance of laminated ME composite, comprises of ferroelectric (FE) layer of BCZT and a ferrite layer of CNZF. However, the ME coupling constant of laminated composite is optimized by lowering volume fraction of FE component to strengthen the mechanical strain in piezoelectric layer, while fixing the thickness of the magnetostrictive ferrite layer. Here, we employed systematic zero field cooled (ZFC) and field cooled (FC) electrical poling protocol on morphotropic phase boundary (MPB) based BCZT composition, well-appreciated for it’s remarkable electromechanical activity. We report a record augmentation in magnetoelectric coupling as a consequence of prudent field cooled poling mechanism. On the basis of our findings, we emphasize that the degree of magnetoelectricity may be significantly improved for miniaturization of efficient devices via proper execution of poling technique.