BiFeO3 PbTiO3 Research Articles

Well-defined polymorph transformation sequences and novel tetragonal twin-domain patterns in the morphotropic phase boundary of Dy-modified BiFeO3–PbTiO3 single crystals

Well-defined polymorph transformation sequences and novel tetragonal twin-domain patterns are found in the MPB of Dy-modified BiFeO3–PbTiO3 single crystals.

Bulk-like ferroelectricity and magnetoelectric response of low-temperature solution-processed BiFeO3–PbTiO3 films on Ni for metallic MEMS

Simple and cost-effective procedures for the direct integration of ferroelectric perovskite oxides into Ni structures are necessary to realize related multifunctional metallic microelectromechanical systems, such as dual-source energy harvesters. This is especially difficult in the case of lead-containing morphotropic phase boundary materials for high piezoelectric response because the two components are thermodynamically incompatible and the formation of NiOx or perovskite oxide reduction takes place depending on the processing conditions. We show here that low-temperature solution processing is an effective means to kinetically limit nickel oxidation, capable of providing BiFeO3–PbTiO3 films on Ni plates at only 500 °C. Bulk-like ferroelectric properties and a distinctive magnetoelectric response were attained. This perovskite system, not explored before on Ni, has a much larger switchable polarization than the widely studied Pb(Zr,Ti)O3, and it is shown here to present an excellent downscaling behavior of ferroelectric properties until the verge of the nanoscale.

Controlling the piezoelectric properties in bulk BiFeO3–PbTiO3–Li0.5Bi0.5TiO3 ceramic by quenching and annealing

Controlling the piezoelectric properties in bulk BiFeO3–PbTiO3–Li0.5Bi0.5TiO3 ceramic by quenching and annealing

Investigation on degree of non-ergodicity and local piezoelectric properties in Na0.5Bi0.5TiO3–BiFeO3–PbTiO3 system

Knowledge of the statics and dynamics of ferroelectric domains is of immense importance since they are directly correlated with macroscopic polarization and strain. For the present work, piezoresponse force microscopy (PFM) is used to afford insight into field-induced phase transitions and local switching properties of a (1–2x)Na0.5Bi0.5TiO3–xBiFeO3–xPbTiO3 system for compositions, x = 0.01, 0.03, 0.05, and 0.07. Rietveld analysis of x-ray diffraction data reveals crystallization of the compound in single and dual phases in the chosen compositions. Upon the application of a local electric field, a phase transition from relaxor to normal ferroelectric (FE) is observed for all samples. A decrease in degree of non-ergodicity is realized within this composition range, which is found by analyzing the stability of field-induced ferroelectric domains. The field-induced FE domains for lower concentrations of x are found to be irreversible and a reversible nature was found for higher values of x. In addition, spatial variations of local switching parameters are investigated with the help of switching spectroscopic-PFM and a maximum local d33 was found for compositions having dual phases.

Structural mechanisms of large piezoelectric responses in BiFeO3-PbTiO3 based solid-solution ceramics

Achieving large piezoelectric response and high Curie temperature, simultaneously, are of great demand but have been rarely achieved in BiFeO3-PbTiO3 (BF-PT) based morphotropic phase boundary (MPB) systems. In this work, in-situ synchrotron x-ray diffraction and transmission electron microscopy were carried out in BF-PT-0.19Ba(Zr,Ti)O3 high-temperature piezoceramic, a recently reported MPB composition with high piezoelectric coefficient, to elucidate the underlying structural mechanism. A field induced irreversible transition from tetragonal (T) P4mm phase to rhombohedral (R) R3c phase is identified although R and T phases are still coexisted after poling. This induces the significantly enhanced irreversible domain switching of both R and T phases and the reversible domain switching of R phase but only a slightly enhanced reversible switching of T phase of as compared with other BF-PT-x Ba(Zr,Ti)O3 MPB compositions, leading to the significant increase of lattice strain up to ∼0.15% but only a slightly increase of strain from extrinsic domain switching due to the strong coupling between lattice strain and domain switching in both R and T phases, although the strain contribution seems to be composition independent after the field induced irreversible phase transition. The present study demonstrates a new performance enhancement mechanism to design the high-performance BF-PT based high-temperature piezoelectric ceramics in terms of the different roles of R and T phases within MPB.

Inducing ferromagnetism and magnetoelectric coupling in the ferroelectric alloy system BiFeO3–PbTiO3 via additives

There is a growing interest in BiFeO3-based alloys because of the possibility it offers for developing high-temperature high-performance piezoelectric materials and for their interesting multiferroic properties. Often such ceramics are synthesized with additives either to reduce/suppress leakage current that the system inherits from the parent compound BiFeO3 or to promote sintering via formation of the liquid phase. We demonstrate here the propensity for stabilizing ferromagnetism in the ferroelectric solid solution BiFeO3–PbTiO3 (BF–PT) when synthesized with additive MnO2. Detailed investigation revealed that the ferromagnetic property of the ceramic is extrinsic and caused by the additive enabled precipitation of trace amount of the ferrimagnetic Pb-hexaferrite phase, not easily detected in conventional x-ray diffraction measurements. We also show that the ferromagnetic property is induced in Co-modified BF–PT. However, in this case, the additive stabilizes the CoFe2O4 spinel ferrite phase. While our findings offer a strategy to develop particulate magnetoelectric multiferroic composites using additive assisted precipitation of the ferrimagnetic phase(s) in BiFeO3-based ferroelectric alloys, it also helps in better understanding of the electromechanical response in BFO-based alloys.

Phase formation and performance of high Curie temperature Bi(Ni0.5Ti0.5)O3–BiFeO3–PbTiO3 ceramics

0.55 Bi(Ni0.5Ti0.5)O3–0.05BiFeO3–0.4PbTiO3 ((0.55BNT–0.05BF–0.4PT)) ceramics were prepared by low-temperature solid-phase sintering method due to adding sintering additives. The 800 °C calcined powders present relatively pure perovskite structure. The 990 °C–1030 °C sintered ceramics exhibit pure perovskite structure, and the density is increased significantly as compared with the undoped ones due to the addition of 0.5 wt% LiBO2. The “0.55BNT–0.05BF–0.4PT” samples sintered at 1010 °C have large density, compact microstructural morphology, high Curie temperature and excellent electrical properties. The ceramics show apparent relaxor ferroelectric behavior and dielectric relaxation characteristic. Grains conduction contributes mainly to the high-temperature conduction, which can be attributed to the migration of oxygen vacancies produced due to the evaporation of ions during sintering.

Structural, capacitive and resistive characteristics of (Pb0.6Bi0.2Sm0.2)(Fe0.4Ti0.6)O3

Samarium substituted BiFeO3–PbTiO3 ceramic compound of (Pb0.6 Sm0.2 Bi0.2)(Fe0.4Ti0.6)O3 has been fabricated by mixed oxide solid state reaction method. The crystallographic structure from XRD study, distribution of grains from SEM micrograph, dielectric behavior, conductivity spectrum, impedance along with electric modulus spectroscopy have been illustrated. The experimental results corroborate the impact of samarium substitution in BiFeO3–PbTiO3 entailing reduced grain size, higher dielectric response with reasonably dielectric loss and enrichment in capacitive behavior with negative temperature coefficient of resistance. The temperature dependent conductivity spectra exhibit Arrhenius behavior, whereas the frequency dependent conductivity spectra follow the Jonscher universal power law. The basic correlated barrier hopping (CBH) model governs the charge transport mechanism in the fabricated compound. The exploration reveals the enriched dielectric and electrical behavior that endorse the samarium substituted material as a potential ceramic entity for designing electronic devices such as capacitors and ferroelectric accessories.

Achieving Large Switchable Polarization and Enhanced Piezoelectric Response in BiFeO3‐PbTiO3 Solid Solution Ceramics

AbstractPerovskite materials based on BiFeO3‐PbTiO3 (BFPT) solid solutions are promising for various applications thanks to the extremely large spontaneous polarization (Ps) and existence of multiferroic morphotropic phase boundary. For applications in piezoelectric and memory devices, complete switching of Ps is needed, which is hard to achieve practically. In this work, a simple modified mixed‐oxide reaction method is developed allowing to prepare Dy‐ and Sm‐modified BFPT ceramics with significantly improved properties. The MPB compositions demonstrate well‐saturated ferroelectric hysteresis loops with large switchable remanent polarization of 60 µC cm−2 and enhanced piezoelectric properties with a large‐signal piezoelectric coefficient d33* = 214 pm V−1 and a direct piezoelectric coefficient d33 = 128 pC N−1, which is one and a half times larger than the best d33 value reported for the BFPT ceramics so far. The Curie temperature reaches 539 °C, suggesting a potential for high‐temperature applications. The domain structure is studied by piezoresponse force microscopy. It is found that the enhanced dielectric/piezoelectric properties are mainly due to polarization rotation/extension (intrinsic) mechanism, while the extrinsic contributions of the interphase and domain walls are virtually absent. The strategies for improvement of properties of BFPT and related materials are proposed.

Additives effect on the multiferroic behaviour of BiFeO3–PbTiO3

The use of additives as a sintering aid for promoting densification is well-known in processing structural ceramics. In leaky ferroelectric ceramics (e.g., BiFeO3-based systems), additives are also used to reduce the leakage current, improve the poling efficiency and the piezoelectric response of a material. A less investigated aspect is how additives affect the multiferroic (ferroelectric and magnetic) features of BiFeO3-based ceramics. In this work, we report a systematic study of the effect of different additives viz, MnO2, CuO, K2CO3 and KMnO4 on the microstructural, electromechanical, and magnetic properties of Dy-modified BiFeO3–PbTiO3. We found that all the additives help in the precipitation of the ferrimagnetic dysprosium iron garnet phase. The additives containing potassium (K) tend to suppress the grain size. We found that the best combination of ferroelectric and ferromagnetic behaviour was found in a mixture of additives.

The evolution of structure and electrical properties for BiFeO3–PbTiO3–Ba(Zr0.3Ti0.7)O3 high-temperature piezoceramics near the morphotropic phase boundary

The development of piezoceramics with high Curie temperature and high piezoelectrical performance has always been a long-cherished goal for many researchers. In this work, we have fabricated 0.55BiFeO3-(0.45-x)PbTiO3-xBa(Zr0.3Ti0.7)O3 ternary ceramics near the morphotropic phase boundary (MPB) by conventional solid-state method. XRD patterns indicate that there is an evolution from the tetragonal (T) to pseudo-cubic (PC) phase with BZT content increasing from 0.125 to 0.225. Also, the slim P-E loop transforms into a saturated shape with the decrease of coercive field Ec. Piezoresponse force microscope (PFM) analysis reveals that when x (BZT content) increases, domain density increases. The optimum piezoelectric coefficient d33 (~220 pC/N) is obtained at x = 0.175, while Curie temperature TC and dielectric loss tanδ are 434 °C and 0.019, respectively. These results show that BF-PT-based piezoceramics are competitive candidates in future high-temperature applications of piezoelectric ceramics.

Role of magnetic ordering in the phase coexistence at the structural instability of the multiferroic BiFeO3–PbTiO3

A promising approach for obtaining a large magnetoelectric response at room temperature in single-phase materials is to make use of phase-change phenomena at structural instabilities of a multiferroic state. This is the case of perovskites showing the morphotropic phase boundary (MPB) between ferroelectric polymorphs with differentiated magnetic orderings, like in BiFeO3–PbTiO3. Indeed, distinctive magnetoelectric effects were recently shown in Mn-modified BiFeO3–PbTiO3, associated with the electric field-induced phase transition between the coexisting MPB phases. We report here analogous effects under the magnetic field in 0.7BiFeO3–0.3PbTiO3, which shed light on the reversibility of the phase-change phenomena and the role of the magnetic ordering in the phase coexistence at the structural instability characteristic of the MPB. Results demonstrate magnetic field-driven phase-change phenomena.

Studies of structural and electrical properties of (Pb0.9Bi0.05Dy0.05)(Fe0.1Ti0.9)O3 ceramic

In this communication, detailed studies of structural, dielectric, and electrical characteristics of dysprosium (Dy)-modified bismuth ferrite–lead titanate (BiFeO3–PbTiO3) solid solution, [i.e., (Pb0.9Bi0.05Dy0.05)(Fe0.1Ti0.9)O3)], prepared by a standard high-temperature solid-state reaction route, have been reported. From the preliminary X-ray structural analysis with Rietveld refinement method, the structure of the material is found to be tetragonal. Detailed analysis of surface morphology, X-ray energy-dispersive spectra and elemental mapping has shown uniform distributions of grains of varying size and elemental composition of the compound. The frequency dependence of the dielectric constant has been explained by the Maxwell–Wagner model. As both the components of the solid solution (BiFeO3 and PbTiO3) have high-temperature ferroelectric transition, no dielectric anomaly has been observed in the said experimental range of our temperature dependence of dielectric studies. The detailed analysis of Nyquist plots, using impedance data collected in a wide range of frequency and temperature shows the contributions of both grains and grain boundaries in the resistive and capacitive characteristics of the prepared material. Both negative and positive temperature coefficients of resistance behaviour are observed in the material. The frequency and temperature dependence of ac conductivity obeys Jonscher’s power law and Arrhenius equation. The occurrence of electric field dependence (P–E) hysteresis loop at room temperature shows the ferroelectric property of the material.

Coexistence of two ferroelectric phases and improved room-temperature multiferroic properties in the (0.70)BiFe1 − xCoxO3–(0.30)PbTiO3 system

In the present time, the focus of many researchers is to enhance the multiferroic properties of pure and doped BiFeO3 (BFO) based materials. However, the materials community has not yet achieved the desired multiferroic properties in single doped BiFeO3. Therefore, we decided to start with the well known system BiFeO3–PbTiO3, with good ferroelectric properties, as compared to undoped BFO and Co2+ as dopant, to obtain the (0.70)BiFe1 − xCoxO3–(0.30)PbTiO3 system. In this paper, the structural, magnetic, and ferroelectric properties of (0.70)BiFe1 − xCoxO3–(0.30)PbTiO3, with 0.00 ≤ × ≤ 0.12, prepared by a simple solgel route is presented. The inclusion of Co2+ leads to notable changes in the structural and magnetic properties. X-ray diffraction studies revealed that the samples crystallize into two ferroelectric phases: rhombohedral (R3c) and tetragonal (P4mm) up to x = 0.06; afterward, it leads to nearly a single phase tetragonal structure for x = 0.09 and 0.12. The magnetic properties are enhanced in a significant manner with Co2+ doping and are ascribed to structural changes (change in Fe–O–Fe bond length) and the suppression of the spiral spin structure characteristic of BiFeO3. The theoretical analysis of the magnetic data shows that the ferromagnetic part also increases with Co2+ doping. Ferroelectric properties are also enhanced with Co doping due to a decrease in the DC current density. The observed room temperature multiferroic properties of this compound foresee great potential for magnetoelectric devices.

Magnetic enhancement of ferroelectric polarization in a particulate multiferroic composite derived in situ via additive assisted sintering of a pseudo ternary alloy system BiFeO3–PbTiO3–DyFeO3

We report here the synthesis of a self-grown 0–3 particulate multiferroic composite by controlled precipitation of the ferrimagnetic garnet phase using additive (MnO2) assisted sintering of a multi-cation ferroelectric system (Bi, Pb, Dy)(Fe, Ti)O3. The particulate multiferroic composite derived in this manner exhibits a favorable microstructure, wherein, although the volume fraction of the garnet phase is kept low (6%), which helps in retaining the electrical insulating character of the specimen, the number fraction of the garnet grains vis-à-vis the ferroelectric grains is ∼1:1. The composite shows a nearly ∼50% increase in saturation polarization at room temperature under a modest magnetic field of 1 T, suggesting a considerable improvement in ferroelectric domain switching due to the efficient strain transfer from the minority garnet grains to the majority piezoelectric grains.

Landau–Devonshire derived phase diagram of the BiFeO3­–PbTiO3 solid solution

Since the construction of the first structural phase diagram of the BiFeO3–PbTiO3 solid solution, there has been ambiguity as to the true location of the morphotropic phase boundary (MPB). In this study, a Landau–Devonshire derived phase diagram has been constructed in order to provide a mathematically derived perspective. The compositional dependence on properties has been modeled as a linear dependence between the Landau coefficients of each end member. It is found that the only structural phases found below TC are rhombohedral and tetragonal, which at 25 °C shows an MPB at 0.696BiFeO3–0.304PbTiO3. The MPB also shows temperature dependence similar to other ferroelectric solid solutions in which the tetragonal–rhombohedral phase transition moves toward higher BiFeO3 contents at higher temperatures. Although the replication of the experimentally observed phase diagram can be constructed, this method is found to be insufficient for describing the spontaneous strain behavior.

Structural, dielectric and electrical characteristics of yttrium modified 0.7BiFeO3-0.3PbTiO3

Some yttrium modified BiFeO3–PbTiO3 (BYFO-PT) compounds have been fabricated using a standard ceramic technology (solid-state route). The structural analysis from X-ray diffraction (XRD) data ensures the formation of the rhombohedral phase of the compounds. The prepared materials have major bismuth ferrite (70%) and lead titanate (30%) with few impurity phases. The materials are found to have a high dielectric constant and low tangent loss. The relaxation mechanism is identified from the peaks appearing in impedance and modulus curves. The materials show a negative temperature coefficient of resistance (NTCR) semiconductor type behavior in the temperature range of 250 °C–400 °C. In addition, grain and grain boundary effects are observed through the Nyquist plots. The activation energy (Ea) of the compounds is calculated from the slope of inverse temperature versus AC conductivity at the high-temperature range. The ferroelectric nature of the compounds is confirmed by electric field dependent polarization (PE-hysteresis) loops.

Temperature and Frequency Dependent Multiferroic Features of Gadolinium Doped BiFeO3-PbTiO3 Electronic System

Multiferroic gadolinium (Gd) doped BiFeO3 (BFO) and PbTiO3 (PT) samples [(Pb1−xBi0.5xGd0.5x)(FexTi1−x)O3] with x = 0.1, 0.3, 0.5 and 0.7 are formulated by adopting the solid state reaction process. The impact of gadolinium substitution in the crystal structure, morphological behavior and electrical properties has been studied. By altering the Gd concentration in the solid solution a change in the structure is observed that is from tetragonal to rhombohedral. The size of the grain in the compounds reduces as a result of enrich in gadolinium content of the furnished sample. The subsidence of lead minimizes the toxic behavior of the material with significant improvements in dielectric response of gadolinium modified BiFeO3–PbTiO3 synthesized system. From the impedance study, the material presents negative temperature coefficient of resistance characteristics and the impedance is due to the presence of grain and grain boundary effect inside the materials. It is realized that the remnant polarization decreases and frequency dependent ac conductivity increases with the concentration of gadolinium in the electronic system. From conductivity study, the equipped electronic materials show non-exponential type of conductivity relaxation.

Influence of Cr3+ doping on multiferroic properties in the morphotropic phase boundary compositions of BiFeO3–PbTiO3 system

In this paper, we have investigated the effect of Cr3+ substitution on the crystal structure, microstructure, dielectric and magnetic behavior of the morphotropic phase boundary (MPB) composition of the multiferroic ceramic 0.675BiFe(1−x)CrxO3–0.325PbTiO3 (x = 0, 0.02 and 0.05). The average grain size of the specimens increased from ~ 150 nm for x = 0 to 470 nm for x = 0.05. Rietveld refinement analysis of the X-Ray powder diffraction patterns confirmed the coexistence of multiphase i.e. monoclinic Cc and tetragonal P4 mm polymorphs for all the compositions. The system exhibits weak ferromagnetism for x = 0.05. We estimated the magnetoelectric interaction constant (γ ~ 0.31) for x = 0.05 by Ginzburg–Landau theory. The value of magnetoelectric coupling coefficient ( $$\alpha_{ME}$$ ) is found to be 0.054 mV/cm-Oe, 0.073 mV/cm-Oe, 0.133 mV/cm-Oe for x = 0, 00.02 and 0.05, respectively. High temperature dielectric data also reveals that Curie temperature decreases with increasing Cr3+ concentration.

Effect of Nd3+ substitution on structural, ferroelectric, magnetic and electrical properties of BiFeO3–PbTiO3 binary system

In this paper, we have reported the effect of rare earth Nd3+ ion substitution on crystal structure, ferroelectric, electrical and magnetic behavior of morphotropic phase boundary (MPB) composition of polycrystalline ceramics 0.7Bi(1−x)NdxFeO3–0.3PbTiO3(BNFPT), where x = 0, 0.05, 0.10. Rietveld refinement of XRD profiles confirms coexistence of rhombohedralR3c and tetragonal P4mmpolymorphs forming MPB for all the compositions. We observed that the remnant polarization Pr increases with increasing Nd3+ concentration. Piezoelectric studies show gradual increase in piezoelectric coefficient (d33) from 11 to 34 pC/N with increase in Nd3+ concentration for BNFPT samples. All compositions exhibit weak ferromagnetic character. For the same composition range, the study of dielectric behavior revealed gradual decrease in Curie temperature (Tc) as we increased doping content of Nd3+.