Coupling Factor K33 Research Articles

Piezoelectric properties and electromechanical coupling factors of a novel 1–1–3 composite with two lead-free ferroelectric components

Abstract A lead-free 1–1–3 composite is put forward for the first time wherein two ferroelectric components (single crystal and ceramic parallel rods) are distributed regularly in the polymer medium. Effective piezoelectric coefficients d3j*, g3j*, e3j*, and h3j*,and electromechanical coupling factors k3j* (j = 1 and 3), kt*, and kp* are studied when changing volume fractions of the lead-free ferroelectric components in the 1–1–3 composite based on [0 0 1]-poled domain-engineered single crystal. Links between the piezoelectric coefficients and electromechanical coupling factors of the composite are studied in a wide range of volume fractions m of single crystal at volume fractions of ceramic mc = 0.03–0.10. New m – mc diagrams show regions of large electromechanical coupling factors k33* ≈ 0.7–0.9 (longitudinal mode) and kt* ≈ 0.7–0.9 (thickness mode), as well as regions where conditions for a large anisotropy | k33* / k31* | ≥ 5 and | kt* / kp* | ≥ 5 hold. The parameters of the novel 1–1– 3 composite are compared to those of the related 1–3-type composites subjected to different averaging procedures and a modification of the ceramic / polymer matrix. The large g33*, h33*,k33*, kt*, | k33*/k31* |, and | kt*/kp* | values of the studied lead-free 1–1–3 composite contribute to its effective use as piezoelectric sensors and transducers operating on longitudinal (or thickness) oscillation modes.

Optimizing High-Power Performance of [001]-Oriented Pb(Mg1/3Nb2/3)-PbTiO3 Through Combined DC and AC Polarization Above Curie Temperature

Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals (PMN-PT SCs) are widely utilized in high-performance piezoelectric devices due to their exceptional piezoelectric properties. Among the various post-processing techniques for domain engineering in PMN-PT SCs, alternating current polarization (ACP) has become a widely adopted method for enhancing piezoelectric performance. This study proposes a new ultrahigh-temperature field-cooling polarization (UFCP) technique, combining direct current polarization (DCP) and ACP with field cooling above the Curie temperature. Dielectric spectra indicate that the UFCP method promotes electric field-induced phase transitions above the Curie point, forming a stable multiphase configuration. The transverse piezoelectric coefficient d31 of UFCP SCs is 1126 pC/N, and the electromechanical coupling factor k31 is 0.559. Compared with traditional DCP, UFCP increases d31 by 68.6%, the mechanical quality factor Qm by 16.7%, and the piezoelectric figure of merit (FOM) by 98.3%. Furthermore, under high-power excitation with a root-mean-square voltage of 15 V, UFCP achieves a 343% increase in power and a 130.5% improvement in the FOM compared with DCP, demonstrating its potential for enhancing high-power performance in practical applications.

Ultrahigh piezoelectric performances of (K,Na)NbO3 based ceramics enabled by structural flexibility and grain orientation

(K,Na)NbO3-based ceramics are deemed among the most promising lead-free piezoelectric materials, though their overall piezoelectric performance still lags behind the mainstream lead-containing counterparts. Here, we achieve an ultrahigh piezoelectric charge coefficient d33 ∼ 807 pC·N−1, along with a high longitudinal electromechanical coupling factor (k33 ∼ 88%) and Curie temperature (Tc ∼ 245 °C) in the (K,Na)(Nb1-xSbx)O3-Bi0.5Na0.5ZrO3-BiFeO3 (KNN-xSb) system through structural flexibility and grain orientation strategies. Phenomenological models, phase field simulations and high-angle annular dark-field scanning transmission electron microscopy reveal that the structural flexibility originates from the high Coulomb force between K+/Na+ ions and Sb ions in the KNN-xSb system, while the grain orientation promotes the displacement of B-site cations leveraging the engineered domain configuration. As a result of its excellent comprehensive piezoelectric properties, the textured KNN-5Sb/epoxy 1-3 piezoelectric composite is found to possess a broader bandwidth BW = 60% and higher amplitude output voltage than commercial PZT-5 and other KNN counterparts. These findings suggest that the textured KNN-5Sb ceramics could potentially replace current lead-based piezoceramics in transducer applications.

Giant Piezoelectric Coefficient of Polyvinylidene Fluoride with Rationally Engineered Ultrafine Domains Achieved by Rapid Freezing Processing.

Domains play an essential role in determining the piezoelectric properties of polymers. The conventional method for achieving ultrafine piezoelectric domain structures for polymers is multiphase polymerization, which is not the primary choice for industrial-scale applications because of its complex synthesis and weak mechanical properties. In this study, it is demonstrated for the first time that a nanoscale domain design can be achieved in a commercially available polyvinylidene fluoride (PVDF) homopolymer through a simple fabrication method involving cyclic compression and rapid freezing. The domain-engineered PVDF exhibits largely enhanced piezoelectric output with a record-breaking piezoelectric coefficient (d33) of 191.4 picocoulombs per Newton (8.9 times higher than that of PVDF without engineered domain structure) and electromechanical coupling factor (k33) of 77.1%. Moreover, nanoscale domain-induced ferroelectric and dielectric evolutions are revealed. A smaller domain is found to be beneficial for domain switching. An in-depth understanding of the interplay between the domain structure and piezoelectric properties reveals a simple, low-cost method for fabricating high-performance polymeric piezoelectric.

Electrical Properties of Textured Bismuth Layer-Structured Ferroelectric Ceramics with Large Number of Layers (m = 5)

Bismuth layer-structured ferroelectrics (BLSF) ceramics are attractive materials for high temperature sensor applications, because of their high Curie temperature Tc (300–900 °C), and the large anisotropy of their electromechanical coupling factor kt/kp or k33/k31. In this study, BLSF ceramics with a large number of layers, namely, (K0.5Bi0.5)2Bi4Ti5O18 + MnCO3 0.3 wt%+ Bi2O3 0.025 wt% (KBT5) and Sr0.75Ca0.25Na0.5Bi4.5Ti5O18 + CeO2 1 wt% [(SC)NBT5] ceramics, were prepared by ordinary firing (OF) and hot forging (HF) methods, and their electrical and piezoelectric properties were examined. Both KBT5 and (SC) NBT5 ceramics showed high Tc values of 545 and 424 °C, respectively. The OF-KBT5 ceramic had an electromechanical coupling factor k33 of 0.14 and a piezoelectric constant d33 of 20 pC/N, whereas the HF-KBT5 ceramic had k33 of 0.17 and d33 of 31 pC/N. On the other hand, the OF-(SC) NBT5 ceramic had k33 of 0.13 and d33 of 17 pC/N, whereas the HF-(SC) NBT5 ceramic had k33 that increased to 0.32 and d33 to 41 pC/N. The k33 and d33 of the HF ceramics were improved compared with those of the OF ceramics. Thus, the KBT5 and (SC) NBT5 ceramics with oriented grains were shown to have good piezoelectric properties with high Tc.

Investigations of high-Performance Ultrasonic Transducers based on PMN-PT Single Crystals

Ultrasonic transducers for NDE applications are commonly based on Lead Zirconate Titanate or PZT, an inorganic compound and ceramic perovskite material. Until now the advantages of PMN-PT are used in medical applications, but are not implemented in NDE. Lead Magnesium Niobate-Lead Titanate (PMN-PT) is well known for its high sensitivity and broad frequency spectrum. While conventional PZT materials have an electromechanical coupling factor K33 (a measure of the conversion between electrical and acoustic energy) of about 0.72, PMN-PT materials reach peak values of more than 0.93. For applications with low signal amplitudes, high electronic noise and small transducer elements, the performance of ultrasonic probes can be significantly enhanced by using Lead Magnesium Niobate-Lead Titanate (PMN-PT) instead of PZT. This single-crystal material offers significantly better piezo parameters and leads to a higher sensitivity and larger bandwidth. There is a better depth resolution possible with this transducers as practical tests have shown. Similar to PZT it can also be fabricated in 1-3 piezo- composite technology. In a cooperation between Fraunhofer IKTS, iBULe Photonics, and IFU Diagnostic Systems, PMN-PT ultrasonic transducers are developed and optimized. The performance of phased array probes and single element transducers was measured by a so called PCUS® pro electronic front end from Fraunhofer and compared with equivalent PZT-based probes. As a result various single element and phased array transducers with im-proved performances are available for NDT of typical aerospace materials and applications. These test setups were used to weigh up the advantages and disadvantages, such as achievable precision or costs, for the implementation of a PMN-PT-based UT matrix probe. Based on this, a wiring variant adapted to the PMN-PT was developed and optimised for the matrix setups by pre- assembling the matching layers. The most favourable setup turned out to be bonding the PMN- PT composites to the prefabricated matching layers together with a rigid-flexible PCB frame. This enabled direct wire bonding of 64 matrix elements to the matching PCB pads on the rigid frame.

Attempt for excellent piezoelectric performance in Sb-free (K,Na)NbO3-based ceramics

Piezoelectric temperature stability is often a very important item for piezoelectric materials when putting them into practical applications like filters and ultrasonic transducers. Phase transitions of (K,Na)NbO3-based compositions that contain neither toxic Pb nor Sb elements were tailored to simultaneously acquire enhanced piezoelectric properties and good piezoelectric temperature stability in this study. Specifically, dense 0.94(K0.48Na0.52)NbO3-0.03BaZrO3-0.01BaSnO3-0.02(Bi0.5Na0.5)ZrO3 ceramic and its further compositionally modified one by 1 wt% MnO2 were prepared. Both of these two ceramics display quite weak piezoelectric temperature dependence in the usage temperature range between −30 °C–100 °C, but the one modified by MnO2 has the significantly improved piezoelectric properties with a high piezoelectric coefficient d33 of 310 pC/N and large electromechanical coupling factors kp and k33 of 0.57 and 0.73 at room temperature. The obtained excellent piezoelectric performance is considered to be associated closely with the stable piezoelectric characteristic of the orthorhombic phase and the diffused rhombohedral-orthorhombic and orthorhombic-tetragonal phase transitions.

Design Optimization of Piezocomposites Using a Homogenization Model: From Analytical Model to Experimentation.

In the process of activating non-conductive smart-structures using piezoelectric patches, one possible method is to add a conductive layer to ensure electrical contact of both electrodes of the ceramic. Therefore, depending on the stiffness and the thickness of this layer, changes in the overall piezoelectric properties lead to a loss in the electromechanical coupling that can be implemented. The purpose of this work is to study the impact of this added electrode layer depending on its thickness. A model of the effect of this layer on the piezoelectrical coefficients has been derived from the previous approach of Hashimoto and Yamagushi and successfully compared to experimental data. This global model computes the variation of all the piezoelectric coefficients, and more precisely of k31 or d31 for various brass electrode volumes relative to the ceramic volume. A decrease in the lateral electromechanical coupling factor k31 was observed and quantified. NAVY II PZT piezoelectric transducers were characterized using IEEE standard methods, with brass electrode thicknesses ranging from 50 to 400 microns. The model fits very well as shown by the results, leading to good expectations for the use of this design approach for actuators or sensors embedded in smart-structures.

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.

Textured BiScO3-PbTiO3 piezoelectric ceramics with both high electromechanical coupling factor and high curie temperature

High-temperature piezoelectric devices require piezoelectric ceramics with high Curie temperatures and high-temperature stability of piezoelectric properties to avoid the depolarization of piezoelectric ceramics during application. However, piezoelectric materials with high Curie temperatures usually have restrained piezoelectric properties. Crystallographic orientation via texture engineering is a practicable way to improve piezoelectric performance. Here, we propose a sintering-aid-assisted template grain growth strategy to texture BiScO3-PbTiO3 ceramics to overcome the low orientation issue that challenges the texturing of BS-PT for decades. By judiciously selecting B2O3-CuO as sintering aids, we fabricated highly ⟨001⟩-textured 0.43BS-0.57PT ceramics with Logtering factors &amp;gt;99.0% that possess high piezoelectric coefficients d33 of 474–612 pC/N while maintaining relatively high Curie temperatures of 370–402 °C. Importantly, this work addresses a long-standing issue presented in BS-PT ceramics, i.e., the low electromechanical coupling property of BS-PT ceramics (k33 &amp;lt; 0.70) by improving the electromechanical coupling factor k33 to 81.2%. The newly designed textured BS-PT ceramics are thought to be promising candidates for the design of high-temperature piezoelectric transducers and actuators.

Inch-Size Molecular Ferroelectric Crystal with a Large Electromechanical Coupling Factor on Par with Barium Titanate.

Molecular ferroelectrics with large piezoelectric responses have long been sought for their advantages of light weight, mechanical flexibility, and easy preparation, in contrast to the widely used inorganic counterparts. Representatively, a molecular ferroelectric crystal [Me3NCH2Cl]CdCl3 (TMCM-CdCl3) has been found to show a large piezoelectric coefficient d33 of 220 pC/N exceeding that of BaTiO3 (You et al. Science2017, 357, 306-309). However, although the d33 of molecular ferroelectrics has achieved great progress, their electromechanical coupling factor k33, which is essential for various piezoelectric applications, including ultrasonic transducers and actuators, was rarely explored and is far below the level of inorganic ferroelectrics. The major reason for this situation is the great challenge of growing large-size crystals which is a key limiting factor for measuring k33. Here, we grew inch-size crystals of organic-inorganic perovskite ferroelectric TMCM-CdCl3 with a high d33 (383 pC/N) for investigating its piezoelectric responses including the k33 (0.483) by the resonance method. Such high k33 (0.483) is much larger than those of other molecular ferroelectrics and competitive with that of BaTiO3 (0.5). In addition, TMCM-CdCl3 has a low elastic modulus of 13.03 GPa, an order of magnitude lower than that of BaTiO3. This finding sheds light on the exploration of large electromechanical coupling factors in molecular ferroelectrics for potential applications in flexible and portable piezoelectric devices.

Piezoelectric acoustic wave characteristics of Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal substrate: A comparative study with and without SiO2 overlay

This paper investigates the excitation and propagation characteristics of a piezoelectric acoustic wave propagating in a rotated Y-cut X-propagating Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) relaxor-based ferroelectric single crystal substrate. Numerical simulations were performed to evaluate the acoustic wave properties by FEM software COMSOL. For comparison, two types of structures are taken into consideration: one is the traditional metal electrode/YX-PIN-PMN-PT and the other is silicon dioxide (SiO2) overlay/metal electrode/YX-PIN-PMN-PT substrate. It is shown that shear-horizontal (SH)-type piezoelectric boundary acoustic waves (PBAW) exist in the SiO2 overlay/metal electrode/YX-PIN-PMN-PT substrate and offer a fairly large electromechanical coupling factor K2 of 30%. Compared to a surface acoustic wave excited in the metal electrode/YX-PIN-PMN-PT substrate, enlarged phase velocity and significantly improved quality factor (∼3500) are simultaneously obtained for SH-type PBAW, which are promising for electromechanical transducer applications with high performance.

Fabrication of ceramic fibers with excellent eletromechanical properties

One-dimensional (1D) piezoelectric materials have been used in many electronic applications due to their high aspect ratio (length/diameter ratio). The modified polysulfone spinning method was used to prepare 0.02Sm-doped 0.47Pb(Mg1/3Nb2/3)O3-0.18PbZrO3-0.35PbTiO3 (abbreviated as Sm-PMN-PZT) ceramic fibres. The grain size and diameter of the Sm-PMN-PZT ceramic fibres were ∼4.5 μm and ∼500 μm, respectively. The piezoelectric coefficient (d33), relative dielectric permittivity (ε33/ε0), and coupling Factor k33 were found to be ∼780 pC/N, ∼6820, and ∼0.71, respectively. Based on the polarization versus electric field and dielectric permittivity versus temperature curves, the spontaneous polarization, coercive field, and Curie temperature were found to be ∼28.33 μC/cm2, ∼7.27 kV/cm, and ∼160 °C, respectively. These results indicated that Sm-PMN-PT ceramic fibres could be used in advanced electromechanical devices where high-performance 1D piezoelectric materials are needed.

Full matrix electromechanical properties of textured Pb(In1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 ceramic

Textured relaxor-PbTiO3 (PT) ceramics possess advantages of crystal-like properties, high composition homogeneity, and low cost, and have, thus, received considerable attention from the piezoelectric community. To promote the applications of textured relaxor-PT ceramics, here we characterize the full electromechanical parameters (elastic, dielectric, and piezoelectric coefficients) and the frequency dependence of the coercive field (EC) for the recently reported textured Pb(In1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 (PIN-PSN-PT) ceramic. Our results show that the textured PIN-PSN-PT ceramic possesses high piezoelectric coefficients (d31 = −365 pC N−1, d33 = 770 pC N−1, and g33 = 40.4 × 10−3 m2 C−1) and electromechanical coupling factors (k33 = 87% and kp = 82%), far outperforming those of the commercial ceramic PZT-5H (d31 = −274 pC N−1, d33 = 593 pC N−1, g33 = 1.97 × 10−2 m2 C−1, k33 = 75%, and kp = 65%). In addition, the textured PIN-PSN-PT ceramic exhibits lower dielectric constants (ɛ33S = 478) compared with PZT-5H and relaxor-PT crystals, which can greatly promote the sensitivity of receiving transducers. Moreover, the textured PIN-PSN-PT ceramic with a high Tr−t (172 °C) shows better thermal stability compared to commercial relaxor-PT crystals (Tr−t &amp;lt; 130 °C). The results presented here will benefit the development of piezoelectric devices made of textured ceramics.

Relaxor ferroelectric polymer exhibits ultrahigh electromechanical coupling at low electric field.

Electromechanical (EM) coupling-the conversion of energy between electric and mechanical forms-in ferroelectrics has been used for a broad range of applications. Ferroelectric polymers have weak EM coupling that severely limits their usefulness for applications. We introduced a small amount of fluorinated alkyne (FA) monomers (<2 mol %) in relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) terpolymer that markedly enhances the polarization change with strong EM coupling while suppressing other polarization changes that do not contribute to it. Under a low-dc bias field of 40 megavolts per meter, the relaxor tetrapolymer has an EM coupling factor (k33) of 88% and a piezoelectric coefficient (d33) >1000 picometers per volt. These values make this solution-processed polymer competitive with ceramic oxide piezoelectrics, with the potential for use in distinct applications.

Temperature-dependent structure and electromechanical properties of Er doped PMN-PT single crystal grown by modified Bridgman technique

In this work, the Er-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal with a large size was successfully grown by the modified Bridgman technique. The temperature dependent phase structure, domain configuration and electromechanical properties of the single crystal with the composition of 2 wt%Er-0.66PMN-0.34PT (Er-0.66PMN-0.34PT) were investigated in detail. For [001]C oriented Er-0.66PMN-0.34PT single crystal, it is found that the room temperature phase structure is the coexistence of rhombohedral (R) and monoclinic (M) phases and M phase is dominated. The piezoelectric constant d33 through the converse piezoelectric effect is about 2410 pC/N. The phase transition from R+M to tetragonal (T) phase begins at 80 ℃ and finishes at 120 ℃. Between 80 ℃ and 120 ℃, the single crystal belongs to the coexistence of R, M and T phases. At 135 ℃, the T phase and polar nanoregions (PNRs) transform into cubic phase and PNRs. The compliance constantss33Dand s33E, longitudinal coupling factor k33 and piezoelectric constant d33 increase by 32%, 77%, 34% and 133%, respectively, with temperature increasing from 22 ℃ to 80 ℃. The ultrahigh increase of d33 is derived from the increase of dielectric constant due to easier polarization rotation and domain wall movement at elevated temperature. Our results will helpful for the study of rare-earth doped relaxor ferroelectric single crystals.

High piezoelectricity after field cooling AC poling in temperature stable ternary single crystals manufactured by continuous-feeding Bridgman method

After field cooling (FC) alternating current poling (ACP), we investigated the dielectric and piezoelectric properties of [001]pc-oriented 0.24Pb(In1/2Nb1/2)O3 (PIN)-0.46Pb(Mg1/3Nb2/3)O3 (PMN)-0.30PbTiO3 (PT) (PIMN-0.30PT) single crystals (SCs), which were manufactured by continuous-feeding Bridgman (CF BM) within morphotropic phase boundary (MPB) region. By ACP with 4 kVrms/cm from 100 to 70 °C, the PIMN-0.30PT SC attained high dielectric permittivity (ε33T/ε0) of 8330, piezoelectric coefficient (d33) of 2750 pC/N, bar mode electromechanical coupling factor k33 of 0.96 with higher phase change temperature (Tpc) of 103 °C, and high Curie temperature (TC) of 180 °C. These values are the highest ever reported as PIMN-xPT SC system with Tpc > 100 °C. The enhancement of these properties is attributed to the induced low symmetry multi-phase supported by phase analysis. This work indicates that FC ACP is a smart and promising method to enhance piezoelectric properties of relaxor-PT ferroelectric SCs including PIMN-xPT, and provides a route to a wide range of piezoelectric device applications.

Optimized piezoelectric properties and temperature stability in PSN‐PMN‐PT by adjusting the phase structure and grain size

AbstractFor relaxor ferroelectric materials, improving the piezoelectric properties and temperature stability simultaneously is still a great challenge up to now. In this work, the structure, electric properties, and thermal stability of xPSN‐(1 − x)PMN‐0.4PT (x = 0.15, 0.29, 0.43, and 0.5) ceramics were studied systematically by experiment and phase field simulation. A high Curie temperature Tc of 255℃ and good longitudinal electricmechanical coupling factor k33 of 0.75 and piezoelectric constant d33 of 650 pC/N are achieved in x = 0.43 ceramics with monoclinic C and tetragonal phases coexistence at room temperature. At 30℃, this composition ceramics sintered at 1260℃ shows the remnant polarization Pr and coercive field Ec are about 36.8 µC/cm2 and 8.2 kV/cm respectively. Moreover, as the temperature increases to 150℃, these values remain as high as 22.6 µC/cm2 and 5.7 kV/cm. In the temperature range of 30–230℃, the variation of k33 and d33 is about 24% and 25%. These high piezoelectric performance and superior temperature stability are related to the more complex domain structures caused by phase coexistence and larger grains with more stable domain structure due to internal stress. The former is beneficial in improving the piezoelectric properties, and the latter dominates the enhanced temperature stability.

Quenching effects on depolarization temperature and &lt;sup&gt;18&lt;/sup&gt;O tracer diffusion in (Bi&lt;sub&gt;0.5&lt;/sub&gt;Na&lt;sub&gt;0.5&lt;/sub&gt;)TiO&lt;sub&gt;3&lt;/sub&gt; ceramics with acceptor and donor additives

Lead-free ferroelectric and piezoelectric ceramics, (Bi0.5Na0.5)TiO3 (BNT), with Mg and Nb additives were prepared and the concentration of oxygen vacancies as the 18O tracer diffusion of these ceramics were clarified by secondary ion mass spectroscopy (SIMS). Moreover, the samples were quenched after sintering to examine the depolarization temperature Td, and then their electrical properties were investigated. As a result, the obtained values of volume diffusion coefficient D of BNT doped with 0.4 wt % Mg and 0.4 wt % Nb were determined to be 9.2 × 10−11 and 1.1 × 10−13 cm2/s, respectively. The oxygen vacancy concentration increased with the amount of Mg added and decreased with that of Nb added. Moreover, quenching increased Td by ∼50 °C in BNT with the Mg additive (Mg x) and ΔTd also increased. Thus, the effect of quenching was promoted by Mg x. On the other hand, the Td of BNT with the Nb additive (Nb y) also increased despite the low concentration of oxygen vacancies. This is because the D of pure BNT (no additives) was revealed found to be 2.5 × 10−11 cm2/s, that is, pure BNT originally contained a high concentration of oxygen vacancies. The concentration was maintained even after quenching, then D showed 1.8 × 10−11 cm2/s. In addition, the electromechanical coupling factor k33 of the quenched ceramics remained similar to that of the ordinarily fired samples of BNT with the Mg and Nb additives.

An analysis of the ferroelastic transition in Pb(Zr0.53Ti0.47)O3:Gd through the elastic stiffness constant

ABSTRACT The values of PZT53/47 doped with 0.6% Gd2O3 show an anomalous behavior near 132°C as a consequence of a ferroelastic transition. A non-linear fit to the experimental data of the elastic stiffness variation shows that it behaves according to the theoretical law describing pseudoproper ferroelastic transitions. Through Raman spectrum analysis, the frequency of soft mode A1(1TO) has a minimum in the 132–136°C temperature interval associated with the coupling to the component of the deformation. The quantitative evaluation of the order parameter by hard mode spectroscopy ratified the occurrence of a ferroelastic phase transition. The behavior of both piezoelectric coefficients d31 and the electromechanical coupling factor k31 can be taken as evidence of the transition showing local maxima at 138°C as a consequence of the maximum deformation during the oscillations of the A1(1TO) mode.