Morphotropic Phase Boundary Composition Research Articles

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.

Investigation of Dielectric Properties of Quaternary Ceramic 0.47BNT-0.04BT-0.37PMN-0.18PT

Dielectric dispersion analysis has been carried out for the first time on a new quaternary ceramic [0.47(Bi0.5Na0.5)TiO3-0.04BaTiO3-0.31Pb(Mg1/3Nb2/3)O3-0.18PbTiO3] having a morphotropic phase boundary composition. The measurement of the dielectric parameters has been carried out in the frequency range of 200 Hz to 2 MHz and temperature range from 30 oC to 300 oC. The material showed high dielectric constant, low dielectric loss, negligible DC conductivity and high ferroelectric to paraelectric transition temperature. A clear Debye type relaxation was observed in the dielectric constant and dielectric loss data. An interesting feature of two Debye peaks has been noticed in dielectric loss versus frequency curves in the temperature range 125 oC to 175 oC. These peaks shift towards higher frequencies when temperature is increased. The extracted relaxation times of the two peaks are three orders of magnitude different and have been found to follow the Arrhenius law with significantly different activation energies.

Tuning the electrical conductivity and Maxwell-Wagner relaxation in BiFeO3–BaTiO3 piezoceramics

Recent research has emphasized the investigation of BiFeO3–BaTiO3 (BFO–BT) piezoelectric ceramics due to their elevated Curie temperature. Nevertheless, the substantial electrical conductivity of these ceramics poses practical challenges. This study evaluates the influence of post-annealing and manganese (Mn) doping on the conductivity, dielectric behavior, and ferroelectric properties of (1-x)BFO–xBT ceramics with a morphotropic phase boundary composition (x = 0.33). The results demonstrate that the conductivity of the ceramics in the as-sintered state is affected by Maxwell-Wagner effects arising from variations in conductivity at grain boundaries. Annealing under specific atmospheres indicates that the electrical conductivity is of the p-type, potentially associated with Fe4+ defects. Furthermore, annealing in a carefully controlled atmosphere or the introduction of Mn doping significantly alleviate these effects, leading to an enhancement in domain switching characteristics. The insights garnered from this investigation regarding annealing and doping have the potential to advance lead-free BFO–BT piezoelectric ceramics.

Achieving High Piezoelectric Performance across a Wide Composition Range in Tetragonal (Bi,Na)TiO3-BaTiO3 Films for Micro-electromechanical Systems.

Tetragonal (1-x)(Bi,Na)TiO3-xBaTiO3 films exhibit enhanced piezoelectric properties due to domain switching over a wide composition range. These properties were observed over a significantly wider composition range than the morphotropic phase boundary (MPB), which typically has a limited composition range of 1-2%. The polarization axis was found to be along the in-plane direction for the tetragonal composition range x = 0.06-1.0, attributed to the tensile thermal strain from the substrate during cooling after the film formation. A "two-step increase" in remanent polarization against an applied maximum electric field was observed at the high-field region due to the domain switching, and a very high piezoelectric response (effective d33 value, denoted as d33,f) over 220 pm/V was achieved for a wide composition range of x = 0.2-0.5 with high tetragonality, exceeding previously reported values for bulk ceramics. Moreover, a transverse piezoelectric coefficient, e31,f, of 19 C/m2 measured using a cantilever structure was obtained for a composition range of at least 10 atom % (for both x = 0.2 and 0.3). This value is the highest reported for Pb-free piezoelectric thin films and is comparable to the best data for Pb-based thin films. Reversible domain switching eliminates the need for conventional MPB compositions, allowing an improvement in the piezoelectric properties over a wider composition range. This strategy could provide a guideline for the development of environmentally acceptable lead-free piezoelectric films with composition-insensitive piezoelectric performance to replace Pb-based materials with MPB composition, such as PZT.

Piezoelectric, ferroelectric and dielectric characterizations of a new ceramic solid solution (1-x)Ba(Cu1/3Nb2/3)O3-xPbTiO3 with morphotropic phase boundary

The understanding of structure-property co-relations is a key to utilising the materials for their best performances. This paper focuses on the physical property characterization of a new binary solid solution series with formula (1-x)Ba(Cu1/3Nb2/3)O3-xPbTiO3. A unique type of crystal structure evolution as a function of composition has been observed for this solid solution series, where a two-phase coexistence is observed in a very large span of compositions at room temperatures. The microstructure, piezoelectric, ferroelectric and dielectric properties along with their entanglement with crystal structure, have been investigated in detail. The compositional homogeneity of selected compositions has been verified with EDS and XPS. The higher responses in the physical properties have been observed near morphotropic phase boundary compositions. On heating above room temperature, peaks in dielectric permittivity responses have been observed that correspond to the phase transitions of non-centrosymmetric phases. The solid solution's best piezoelectric and ferroelectric responses are observed for the x = 0.70 composition showing higher densification, larger grain size and low dielectric losses, and lies near the morphotropic phase boundary region. The solid solution has enormous potential in piezoelectric industries as it possesses morphotropic phase boundary and high-temperature piezoelectricity.

Designing high piezoelectric properties at the BaTiO3–PbZrO3–PbTiO3 phase boundary by Landau–Devonshire theory

Ferroelectric materials possessing exceptional piezoelectric attributes have garnered widespread utilization in various applications. Solid solution systems improve piezoelectric properties through multiphase mixing, but the methodologies for effective design remain wanting. Based on the Landau–Devonshire theory, we propose a theoretical design method. Binary materials with morphotropic phase boundary (MPB) compositions are added with new elements to increase the free energy of the original stabilized phase and lower the energy barrier (EB). Flatter EBsand higher piezoelectric coefficients are found at the phase boundaries of the ternary system. By calculating the phase diagram, piezoelectric coefficient, dielectric constant, polarization, and EBs, we reveal the origin of the highest piezoelectric coefficient at the phase boundaries. This study underscores the importance of the EBs for polarization rotation in characterizing piezoelectric properties and proposes a theoretical design method for exploring materials with high piezoelectric coefficients.

Large piezoelectricity with enhanced thermal stability in BiScO3-BiInO3-PbTiO3 ternary perovskite ceramics

Simultaneously achieving large piezoelectricity and excellent thermal stability in a piezoceramic is highly desired for constructing advanced high-temperature electromechanical coupling devices. Here, a large high-temperature piezoelectric coefficient (d33 = 523 pC/N at 200 °C) with a small fluctuation rate (η ≤ ±10 %) over an ultra-broaden temperature range of 48–342 °C was achieved in novel zBiScO3-xBiInO3-yPbTiO3 (zBS-xBI-yPT) ternary perovskite piezoceramics with a high Curie temperature of 440 °C. The morphotropic phase boundary (MPB) of multiphase coexistence can be driven and optimized in this system, which is mainly responsible for the enhanced piezoelectricity, and the optimal MPB composition is located at x/y/z = 0.010/0.625/0.365. The excellent temperature stability of the optimal MPB sample should be attributed to the increase in the number of thermally stable irreversible non-180° domains. zBS-xBI-yPT perovskite ceramics with excellent comprehensive high-temperature piezoelectric properties exceed many reported lead-based counterparts, and are more suitable for electromechanical coupling applications at harsh elevated temperatures.

Achieving ultrahigh electromechanical properties with high TC in PNN-PZT textured ceramics

<001> textured Pb(Ni1/3Nb2/3)O3-PbZrO3-PbTiO3 (PNN-PZT) ceramics were prepared by templated grain growth (TGG) technique using 0.36PNN-xPZ-(0.64-x)PT (x = 0.23, 0.25 and 0.27) powder matrix. Optimum template content was derived to achieve the best electromechanical properties of textured ceramics. The piezoelectric coefficient d33 = 1165 pC/N, Curie temperature TC = 197 °C, longitudinal mode electromechanical coupling factor k33 = 0.86 and a very large effective piezoelectric strain coefficient d33* = 2041 pm/V were simultaneously achieved at the morphotropic phase boundary (MPB) composition (x = 0.25) with 3 vol.% BaTiO3 (BT) templates. Domain structures of textured ceramics were analyzed in detail to reveal the origin of these high piezoelectric and electromechanical properties.

Outstanding piezoelectric performance of BiScO3-PbTiO3-based ceramics over a wide high-temperature region

Piezoceramics with high piezoelectric performance in a wide elevated temperature range are the best potential stocks used in advanced high-temperature piezoelectric devices. Here, novel ternary perovskite piezoceramics of (0.997-x)BiScO3-xPbTiO3-0.003Bi(Zn2/3Nb1/3)O3 (BS-xPT-BZN) are synthesized and investigated. The morphotropic phase boundary (MPB) composition of the BS-xPT-BZN system is located at x = 0.625, which exhibits a high Curie temperature (TC) of 442 °C. More excitingly, the in-situ piezoelectric coefficient (d33) of the x = 0.625 MPB sample is not only as high as 558 pC/N at 200 °C, but also has a fluctuation rate of less than ± 10 % in the ultra-wide high-temperature range of 100 ∼ 308 °C. The above excellent comprehensive high-temperature piezoelectric performance should be attributed to the synergistic effect of composition-related MPB and dispersion characteristics and thermally stable ferroelectric domain state. The results demonstrate that BS-xPT-BZN ceramics can be used as very competitive perovskite piezoelectrics to construct piezoelectric devices for applications in harsh high-temperature environments.

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.

Bismuth as antiferroelectric phase-stabilizer in Pb(ZrSn)TiO3: Designing of a material with large strain and shape memory effect

This work highlights antiferroelectric (AFE) phase stabilizing effect of Bi substitution at the A-site in Pb[(Zr0.7Sn0.3)0.938Ti0.062]O3. The composition Pb0.985Bi0.01(Zr0.7Sn0.3)0.938Ti0.062O3 with 1% Bi substitution lies just outside the morphotropic phase boundary (MPB) toward the AFE side and allows an electric field driven atomic rearrangement for a disordered state. The disorder and randomness introduced through this substitution is seen to impact the electromechanical property like strain, quite drastically (Smax ∼ 0.3%). Keeping the optimal Bi inclusion and Zr: Sn as 70:30, the B-site of Pb0.985Bi0.01[(Zr0.7Sn0.3)xTi1-x]O3, is varied. The system is brought back to MPB for x = 0.933, and strain values of Smax ∼ 0.44% and a remnant strain Srem ∼ 0.27% are obtained for the optimized MPB composition Pb0.985Bi0.01[(Zr0.7Sn0.3)0.933Ti0.067]O3.

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 Nb substitution on the electronic property of lead-free piezoelectric (Na0.41K0.09Bi0.50)TiO3 single crystal: Optical absorption and photoelectron study

Single crystals of undoped and Nb doped sodium and potassium-bismuth titanate at the morphotropic phase boundary (MPB) composition [(Na0.41K0.09Bi0.50)TiO3: NKBT] were grown from high temperature solutions. The effect of Nb doping on the electronic property of NKBT was investigated by optical transmission and photoelectron spectroscopy (PES). The optical absorption shows that the bandgap having the lowest energy is indirect in nature and increases with the increase in the Nb concentration in the lattice. The estimated Urbach energy increases with the increase of Nb concentration signifying an increase in the disorder in the lattice on Nb doping. The PES revealed that the valence band maxima (VBM) exhibit red shift on Nb doping. It also revealed the presence of in-gap states probably due to Ti3+ defect and oxygen vacancy. Moreover, inline with the optical measurement, the PES showed that there is a decrease in the energy gap between the VBM and defect state with the Nb doping. Furthermore, the angle resolved PES measurement confirmed the presence of both the direct and indirect bandgaps in the crystal.

Large Thermal Conductivity Switching in Ferroelectrics by Electric Field-Triggered Crystal Symmetry Engineering

A convenient, reversible, fast, and wide-range switching of thermal conductivity is desired for efficient heat energy management. However, traditional methods, such as temperature-induced phase transition and chemical doping, have many limitations, e.g., the lack of continuous tunability over a wide temperature range and low switching speed. In this work, a strategy of electric field-driven crystal symmetry engineering to efficiently modulate thermal conductivity is reported with first-principles calculations. By simply changing the direction of an external electric field loaded in ferroelectric PbZr0.5Ti0.5O3, near the morphotropic phase boundary composition, we obtain the largest switching of thermal conductivity for ferroelectric materials at room temperature based on the dual-phonon theory, i.e., normal and diffuson-like phonons, with three different criteria. The calculation results indicate that with decreasing crystal symmetry, the degeneracy of phonon modes reduces and the avoid-crossing behavior of phonon branches enhances, leading to the increase of diffuson-like phonons and weighted phonon-phonon scattering phase space. A thermal switch prototype based on PbZr0.5Ti0.5O3 is further shown that can protect the Li-ion battery by modulating its temperature up to 17.5 °C. Our studies would pave the way for designing next-generation thermal switch with high speed, a wide temperature range, and a large switching ratio.

Piezoelectric Properties of {110}-Oriented A-Site Sr-Substituted Pb(Zr0.80Ti0.20)O3 Thin Films

A-site Sr-substituted Pb(Zr0.80Ti0.20)O3 composition (PSZT) with different Sr2+ content in the range, 0.15 ≤ x ≤ 0.20, and located near the AFE-FE phase boundary hold promise for microactuator applications. Thin films of PSZT with 1.0 µm thickness were fabricated on silicon substrates by chemical solution deposition by spin coating. The structure and texture of the thin films were determined through Raman spectral and XRD studies. We report, for the first time, the existence of the monoclinic phase in the AFET-FER morphotropic phase boundary (MPB) compositions. Correlation of piezoelectric constant, e31,f of the thin films and their texture is also reported.

Refractive index and domain structure of undoped and Nb doped (Na0.41K0.09Bi0.50)TiO3 (NBT-KBT) single crystal grown at MPB composition

Single crystals of undoped and Nb doped NBT-KBT with morphotropic phase boundary composition [(Na0.41K0.09Bi0.50)TiO3] were grown by spontaneous nucleation technique. The lattice parameter was found to be unaffected on Nb doping. Further the temperature dependent refractive indices were measured for four different wavelengths and the Sellmeier coefficients were calculated in the range of 30–160 °C. Refractive index was found to increase linearly with temperature (thermal coefficient of refractive index ∼10−4-10−5/°C). Further, the thermal coefficient was found to increase with the Nb concentration. A set of relations of the thermal coefficient of refractive index as a function of wavelength was established. In addition, the crystal was investigated using polarized light optical microscope. Regions with both ‘a’ and ‘c’ domains, typical of tetragonal structure, were observed in the samples. Further, the conoscopic study revealed that the material is of negative uniaxial type. The presence of domains related to the tetragonal and rhombohedral structures hints the possible coexistence of both the structures as expected for the morphotropic phase boundary composition. The outcome of the investigation would provide valuable inputs about NBT-KBT single crystals for photonic or optoelectronic applications.

Effect of A-site covalency on ferroelectric phase transition in Ba doped morphotropic phase boundary PbTiO3–BiFeO3 solid solutions

This work investigates the role of A-site chemical bonding in morphotropic phase boundary (MPB) compositions of PbTiO3–BiFeO3 solid solutions exhibiting high tetragonality. Ba substitution significantly reduces the ferroelectric critical temperature, which correlates well with the structural parameters and manifests marked change in the free energy profile of structural phases within the MPB regime. A reduction in the grain size with Ba substitution has been observed which shows the reduction in the grain growth with Ba incorporation. The presence of pinned defect dipoles has been confirmed from the observed elliptical hysteresis loops at room temperature, making high-temperature permittivity studies unique to unraveling the finer details of this system. Inter and Intra grain contributions in the electrical response are quantified from the equivalent circuit analysis and compared with the complex permittivity profile. The frequency and temperature-dependent ac conductivity responses were analyzed, and observed conductivity was related to charge carriers hopping between vacant sites.

Ultrahigh Energy Storage Density in Glassy Ferroelectric Thin Films under Low Electric Field.

The current approach to achieving superior energy storage density in dielectrics is to increase their breakdown strength, which often incurs heat generation and unexpected insulation failures, greatly deteriorating the stability and lifetime of devices. Here, a strategy is proposed for enhancing recoverable energy storage density(Wr ) while maintaining a high energy storage efficiency (η) in glassy ferroelectrics by creating super tetragonal (super-T) nanostructures around morphotropic phase boundary (MPB) rather than exploiting the intensely strong electric fields. Accordingly, a giant Wr of ≈86 J cm-3 concomitant with a high η of ≈81% is acquired under a moderate electric field (1.7 MV cm-1 ) in thin films having MPB composition, namely, 0.94(Bi, Na)TiO3 -0.06BaTiO3 (BNBT), where the local super-T polar clusters (tetragonality ≈1.25) are stabilized by interphase strain. To the knowledge of the authors, the Wr of the engineered BNBT thin films represents a new record among all the oxide perovskites under a similar strength of electric field to date. The phase field simulation results ascertain that the improved Wr is attributed to the local strain heterogeneity and the large spontaneous polarization primarily is originated from the super-T polar clusters. The findings in this work present a genuine opportunity to develop ultrahigh-energy-density thin-film capacitors for low-electric-field-driven nano/microelectronics.

Boosting the piezoelectric property of relaxor ferroelectric single crystal via active manipulation of defect dipole polarization

To further enhance the property of piezoelectric materials is of great significance to improve the overall performance of electro-mechanical devices. Here in this work, we propose a thermal annealing and high temperature poling approach to achieve significantly enhanced piezoelectricity in Pb(In1/2Nb1/2)O3Pb(Mg1/3Nb2/3)O3PbTiO3 (PIN-PMN-PT) crystals with a morphotropic phase boundary (MPB) composition. The main idea of our approach is to realize a more sufficiently polarized crystal via active manipulation of defects and orientation of defect polarization. Manipulation of defect dipoles by the high temperature poling is proved by the piezo-response force microscopy. Finally, a d33 of 3 300 pC/N and a SE of 0.25% are obtained, nearly 60% higher than that of conventionally poled crystals. Moreover, such a boosting of piezoelectric property is obtained under a maintained Curie temperature. Our research not only reveals the active control of defect dipole via modified poling method in the PIN-PMN-PT crystal, but also provides a feasible strategy to further improve the property of piezoelectric materials.