Rhombohedral Side Research Articles

Effects of Sm-substitution on dielectric, ferroelectric, and piezoelectric properties of 0.36(Bi1-xSmx)ScO3-0.64PbTiO3 ceramics

Dielectric, ferroelectric, and piezoelectric properties of 0.36(Bi1-xSmx)ScO3-0.64PbTiO3 (BSPT-xSm) ceramics were investigated to assess effects of Sm-substitution on 0.36BiScO3-0.64PbTiO3 for high temperature piezoelectric device application. Optimal sintering was achieved at 1200°C when the BSPT-xSm ceramics were fully densified and crystallized with a perovskite structure without any secondary phase. The substitution of Bi3+ with Sm resulted in degradation of rhombohedral side in BSPT-xSm ceramics having morphotropic phase boundary. In addition, variations of grain size and ferroelectric behavior after Sm-substitution were insignificant. However, dielectric constant (εT33/ε0) was significantly enhanced with an increasing of amount of Sm to 5%. Although a slight decrease of relative density in case of x exceeding 3% led to deterioration of piezoelectric values of d33, kp, and d33*, the BSPT-3%Sm ceramic exhibited excellent values of d33 of 628 pC/N, kp of 62.4%, and d33* of 718 pm/V at 4.5 kV/mm, along with a high ferroelectric transition temperature of 421°C. The highly increased diffusion coefficient of 1.909 also implies that the Sm-substitution contributed to relaxor-like ferroelectric behavior of BSPT ceramics.

Photoluminescence effects and probing phase transition of Sm3+-doped Ba(Ti0.8Hf0.2)O3-(Ba0.7Ca0.3)TiO3 phosphor prepared by hydrothermal method

A series of [(Ba(1-0.3y)Ca0.3y)1-xSmx][Ti(0.8+0.2y)Hf(0.2-0.2y)]O3 (Sm3+-doped (1-y)Ba(Ti0.8Hf0.2)O3-y(Ba0.7Ca0.3)TiO3, abbreviated as Sm3+-doped BCTH, or (1-y)BHT-yBCT:xSm3+, x = 0.0005–0.03, y = 0.2–0.7, y representing the mole fraction of (Ba0.7Ca0.3)TiO3) nano phosphors were prepared by a hydrothermal method. The Sm3+ ions doping amount and triple-point morphotropic phase boundary (TMPB) composition dependent photoluminescence properties were systematically investigated. The hydrothermal synthesized powders present rather pure pseudo-cubic perovskite phase structure at room temperature and locate on the rhombohedral side of MPB. Under the excitation of 409 nm light, the powders exhibit dominant orange-red emission peaks with characteristic emission of the Sm3+ ions at around 564 nm, 596 nm, 644 nm, and 703 nm, relating to the transitions of 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The BHT-0.5BCT:0.005Sm3+ powder exhibits optimal emission in these Sm3+-doped BCTH powders. Furthermore, the phase transition temperature can be characterized by the multi-feature changes of the temperature dependent fluorescence intensity.

Accelerated discovery of high-performance piezocatalyst in BaTiO3-based ceramics via machine learning

The study of piezocatalysis has become an important topic in piezoelectric research, especially for addressing environmental issues. However, the reliance on nanofabrication seriously hinders investigating materials with complex compositional design for higher performance and large-scale application. In this work, we use a machine learning strategy to efficiently sample the vast compositional space for ceramic powders with excellent piezoelectric response that we expect to impact piezocatalytic performance. The ceramics, synthesized by solid state reaction methods, belong to the multi-component system (Ba1−x−yCaxSry)(Ti1−u−v−wZruSnvHfw)O3 with target property d33, the piezoelectric coefficient. The highest d33 tends to occur within the phase boundary region with coexisting rhombohedral, orthorhombic and tetragonal phases, especially on the rhombohedral phase side. We select (Ba0.95Ca0.05)(Ti0.9Sn0.1)O3 as it combines a relatively large d33 with the fewest number of elements. Its sintered ceramic exhibits a high d33 of 605 ± 14 pC/N, consistent with the machine learning prediction 633 ± 70 pC/N. The mechanically-ground ceramic powders have an excellent piezocatalytic activity with a degradation rate of (2.16 ± 0.28) × 10−2 min−1 for RhB dye solution, comparable to the performance of previously reported nanoparticles. Our work provides further insight into the nature of piezoelectricity in BaTiO3 based ceramics, and affords an effective strategy for searching for superior piezocatalysts suitable for large-scale applications.

Ultrahigh piezoelectricity in (Ba,Ca)(Ti,Sn)O3 lead-free compounds with enormous domain wall contribution

The development of lead-free piezoelectric ceramics with high piezoelectric coefficient d33 is of great demand to replace lead-based counterparts. However, a plateau of the piezoelectricity has been reached over years for lead-free ceramics through traditional strategies of constructing phase boundary. Here, we introduce a new strategy in a ternary 0.818BaTiO3-(0.182-x)CaTiO3-xBaSnO3 system close to the rhombohedral side of the tetragonal-orthorhombic-rhombohedral phase boundary, where an ultrahigh d33 value up to ∼860 pC N−1, higher than that of most lead-based piezoelectric ceramics and nearly all lead-free ceramics, can be realized at x = 0.108. Nonlinear dielectric and piezoelectric measurements, in-situ synchrotron x-ray diffraction and composition-dependent domain morphology evolution reveal significantly enhanced domain wall mobility after the composition substitution, contributing to almost ∼80% of the whole d33 value. Such a large piezoelectric coefficient together with a low piezoelectric hysteresis (8%) demonstrates good practical application potentials of high performance soft lead-free piezoelectric ceramics. The current study also provides a new paradigm for largely enhancing the piezoelectric coefficient of lead-free piezoelectric phase-boundary compositions.

Investigation on microscopic mechanisms of high-Curie temperature PMN-PH-PT piezoelectric ceramics

High-Curie temperature (TC) piezoelectric ceramics 0.15Pb(Mg1/3Nb2/3)O3-0.38PbHfO3-0.47PbTiO3 (0.15PMN-0.38PH-0.47PT) were fabricated via the citrate method, which shows pure perovskite structure. The ceramics have composition locating at the rhombohedral side around the morphotropic phase boundary (MPB), and present enhanced electrical properties as compared with those prepared by the solid-state reaction method via the columbite precursor technique. Temperature-dependent Raman spectroscopy not only proves the occurrence of the ferroelectric to paraelectric phase transition around TC, but also detects the successive phase symmetry transitions, which correlate with the polar nanoregions (PNRs) or the coexistence of multiple ferroelectric phases. Large quantities of fine stripe nanoscale ferroelectric domains are observed by piezoresponse force microscopy (PFM) in the 0.15PMN-0.38PH-0.47PT ceramics, which form the larger micron island domains. Temperature-dependent Raman spectra and PFM results indicate that the excellent dielectric, ferroelectric and piezoelectric properties of the 0.15PMN-0.38PH-0.47PT ceramics can be attributed to either the existence of the PNRs with low symmetry or the multiple-ferroelectric-phases coexistence around room temperature and the fine stripe ferroelectric domains.

Phase-field simulation of magnetic microstructure and domain switching in (Tb0.27Dy0.73)Fe2 single crystal

The morphotropic phase boundary (MPB), separating two ferroic phases with rhombohedral and tetragonal crystal symmetries, has been utilized extensively in ferroelectrics because it can lead to high-performance piezoelectricity. Recently, a parallel ferromagnetic MPB was experimentally reported and was suggested that the optimal point for magneto-mechanical applications might lies on the rhombohedral side. However, the insight of the domain structures and switching mechanism near ferromagnetic MPB is still unclear. In this work, phase-field micromagnetic microelastic modeling was employed to simulate the domain formation and magnetization switching of (Tb0.27Dy0.73)Fe2, whose composition is around the rhombohedral side of ferromagnetic MPB. The results show that four kinds of domains of the rhombohedral phase automatically form twins of {110} or {100} boundaries with 71° and 109° domain walls after a process of nucleation and growth. The rhombohedral domain evolution and phase volume fraction under the external field of 120 kA/m along different directions are investigated. In ferromagnetics subject to an alternating magnetic field, domain magnetization switches to cause a magnetization hysteresis loop and an associated butterfly magnetostriction loop with the alternating magnetic field.

Effects of Nano-Sized In2O3 on Sintering Behavior and Electrical Properties of 0.28Pb(In1/2Nb1/2)O3-0.40Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 Ceramics

0.28Pb(In1/2Nb1/2)O3-0.40Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 ceramics were synthesized by conventional solid-phase method using nano-sized In2O3. All the sintered 0.28PIN-0.40PMN-0.32PT ceramics have pure perovskite structure with composition locating at rhombohedral side around the morphotropic phase boundary (MPB) region. The 0.28PIN-0.40PMN-0.32PT ceramics belong to displacive driving ferroelectrics with apparent diffused phase transition characteristic. Although the rhombohedral-tetragonal ferroelectric phase transition temperature (TR-T) increases only to ∼120 °C due to the solid solution of Pb(In1/2Nb1/2) (PIN), the 0.28PIN-0.40PMN-0.32PT ceramics present high piezoelectric thermal stability till around the Curie temperature (Tm), which extremely widens the working temperature range and makes the 0.28PIN-0.40PMN-0.32PT ceramics suitable for high-temperature piezoelectric applications.

Relationship between composition and electromechanical properties of CuO-doped textured PYN-PMN-PT ceramics

This study reports the effects of composition and the presence of residual template particles on the electromechanical properties of random and textured CuO-doped Pb(Yb1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics. Fully textured PYN-PMN-PT ceramics were produced with [001]-oriented barium titanate (BT) particles. The strain of all textured compositions was improved by 40–82 %, and the coercive field was increased by −1 kV/cm relative to ceramic compositions. Textured 20PYN-46PMN-34PT ceramics had the best combination of properties including a high Ec of 9.8 kV/cm and a low strain hysteresis of 8.5 %. Rayleigh analysis of textured PYN-PMN-PT ceramics showed that more rhombohedral compositions have greater strain because of improved extrinsic and intrinsic contributions to the piezoelectric response. These results demonstrate that textured PYN-PMN-PT is a promising material for high power transducers, however compositions must be sufficiently on the rhombohedral side of the morphotropic phase boundary to compensate for the phase-shifting effects of residual stresses from residual BT template particles.

Ultrasensitive magnetostrictive responses at the pre-transitional rhombohedral side of ferromagnetic morphotropic phase boundary

The morphotropic phase boundary (MPB) has been utilized extensively in ferroelectrics and recently been extended to ferromagnets, especially for the magnetostrictive materials. Here, guided by phenomenological theories and phase-field simulations, we proposed a design strategy for obtaining the ultrasensitive magnetoelastic response at the pre-transitional rhombohedral side of ferromagnetic MPB, by further flattening the energy landscape while maintaining large intrinsic magnetostriction. To validate this, we judiciously introduced the light-rare-earth-based $$\hbox {Tb}_{0.1}\hbox {Pr}_{0.9}$$ system to the Co-doped $$\hbox {Tb}_{0.27}\hbox {Dy}_{0.73}\hbox {Fe}_{2}$$ alloy, as $$\hbox {Tb}_{0.1}\hbox {Pr}_{0.9}$$ is an anisotropy compensation system with large intrinsic strains and the transition metal dopant of Co tends to optimize the magnetostriction. Phase-field modeling was used to determine the detailed magnetic domain evolution of the investigated multi-component Laves phase compounds, the results of which were compared with experimental results. At room temperature, an ultrahigh magnetoelastic response $${d}_{33}$$ was found in $$\hbox {Tb}_{0.253}\hbox {Dy}_{0.657}\hbox {Pr}_{0.09}(\hbox {Fe}_{0.9}\hbox {Co}_{0.1})_{2}$$ recompensation system especially at low fields, which is superior to that of the commercial $$\hbox {Tb}_{0.27}\hbox {Dy}_{0.73}\hbox {Fe}_{2}$$ (Terfenol-D) polycrystal. The ultrahigh magnetostrictive sensitivity, together with low raw material cost makes it one of the strongest candidates for magnetostriction applications.

Symmetry-bridging phase as the mechanism for the large strains in relaxor-PbTiO3 single crystals

Relaxor-PbTiO3 piezoelectric single crystals have been of a great interest, since the discovery of ultrahigh piezoresponse demonstrated in <001> -oriented crystals of the composition at the rhombohedral side of morphotropic phase boundary. It has been proposed that the exceptionally large piezoelectric properties should originate from an electric-field-induced polarization rotation that involves a reversible phase transformation between rhombohedral and tetragonal via monoclinic symmetry. However, this commonly accepted polarization rotation mechanism has its limit in explaining still the excellent piezoelectricity even at a small excitation field far below the coercive field. Here, we show by a comparative study using single crystals from two distinct processing techniques, the polarization rotation has, if ever, little influence on the strain properties of <001 > -oriented rhombohedral relaxor-PbTiO3 single crystals. Instead, they may come from a reversible shear-mode piezoelectric contribution from electric-field-susceptible ‘symmetry-bridging’ unit-cell-level phases, the polarization direction of which spans monoclinic symmetry.

Is there a spontaneous ferroelectric phase transition in 0.83PbMg1/3Nb2/3O3-0.17PbTiO3 single crystal?

The macroscopic response of 0.83PbMg1/3Nb2/3O3-0.17PbTiO3 (PMN-17PT) single crystals has been investigated in order to resolve existing controversy about the structural phase transition in the rhombohedral side of (1-x)PbMg1/3Nb2/3O3-xPbTiO3 phase diagram. The combination of nonlinear dielectric spectroscopy, temperature dependant polarization and strain hysteresis loop measurements and ultrasonic spectroscopy revealed that ferroelectric phase occurs spontaneously in PMN-17PT single crystals. The experimental techniques applied in this work probe the bulk of the sample and can unambigously determine the existence of a spontaneous ferroelectric phase.The experiments showed that zero-field cooled sample has a normal ferroelectric hysteresis loop at room temperature. The electric-field dependence of induced polarization revealed that at a certain electric field the sample undergoes transformation from polydomain to monodomain-like states. The 1 s t order phase transition at 330 K was evidenced by the third order nonlinear dielectric susceptibility for monodomain sample. The nonlinear dielectric response of an unpoled sample does not show such abrupt jump and is more similar to the response of canonical relaxor PbMg1/3Nb2/3O3.Zero-field heating and zero-field cooling experiments also revealed very slow domain formation processes appearing at 300–320 K temperature. They are affected by the experimental conditions. There are evidences that on cooling the domains tend to grow in the sample.

Quenching effects on piezoelectric properties and depolarization temperatures of (Bi0.5Na0.5)TiO3-based solid solution systems

Lead-free ferroelectric and piezoelectric ceramics, (Bi0.5Na0.5(1−x)Li0.5x)TiO3 and (1 − y)(Bi0.5Na0.48Li0.02)TiO3–yBaTiO3 (abbreviated as BNLT100x and BNLBT4-100y, respectively), were fabricated by a quenching procedure after sintering, and then their electrical properties were investigated with the aim of increasing their depolarization temperature Td. From the measurements by a resonance–antiresonance method, the electromechanical coupling factors k33 of BNLT100x and BNLBT4-100y were exactly the same after the quenching treatment as compared with the nonquenched one. The Td of all BNLT100x quenched from 1100 °C reached around 240 °C, and they are almost 60 °C higher for x = 0, 0.02, 0.04, and almost 80 °C higher for x = 0.08 than those of nonquenched ceramics. We also found, from the measurement on BNLBT4-100y quenched from 1100 °C, that the Td values were enhanced to higher temperature by the quenching treatment, even in the case of rhombohedral side (100y < 6), tetragonal side (100y > 6), and MPB composition (100y = 6). Moreover, we confirmed that the rhombohedrality 90-α and the tetragonality c/a values were enhanced by the quenching treatment. This result revealed that, even in the tetragonal symmetry, the lattice distortion (tetragonality) could also be stabilized by the quenching treatment in BNT-based solid solution ceramics.

Optimizing structure and electrical properties of high-Curie temperature PMN-PHT piezoelectric ceramics via tailoring sintering process

Pseudo-ternary high-Curie temperature 0.15Pb(Mg 1/3 Nb 2/3 )O 3 -0.4PbHfO 3 -0.45PbTiO 3 (PMN-PHT) piezoelectric ceramics were prepared by the conventional ceramic processing via the columbite precursor method. The influences of sintering temperature and sintering time on structure and electrical properties of the PMN-PHT ceramics were investigated in order to tailor their performance further. The sintered PMN-PHT ceramics exhibit pure perovskite structure with composition locating at the rhombohedral side around the morphotropic phase boundary (MPB) of the PMN-PHT system. The PMN-PHT ceramics sintered at 1260 °C for 2 h exhibit the best dielectric, ferroelectric and piezoelectric properties. The high piezoelectric response of the PMN-PHT ceramics is considered as relating to the MPB effect and their dense microstructure obtained via tailoring sintering conditions. The sintered PMN-PHT ceramics exhibit good thermal stability of piezoelectricity and ferroelectricity within the common usage temperatures, indicating that such ceramics are promising candidates for piezoelectric devices at elevated temperatures.

Enhancing piezoelectric properties of BCZT ceramics by Sr and Sn co-doping

1mol% Sr and 1mol% Sn co-doped (Ba0.84Ca0.15Sr0.01)(Ti0.90Zr0.09Sn0.01)O3 (BCSTZS) ceramics were prepared by the conventional solid-state reaction method. The sintered BCSTZS ceramics exhibit pure perovskite structure with composition locating at the rhombohedral side around the morphotropic phase boundary (MPB) of the BCZT system. With the increase of sintering temperature, the grains grow up, porosity eliminates and microstructure becomes dense accompanied by the improvement of electrical properties of the synthesized BCSTZS ceramics. Although the grain size of the BCSTZS ceramics sintered at elevated temperatures is rather “small”, they still exhibit excellent electrical properties, which can be attributed to the MPB effect and the dense microstructure induced by the Sr and Sn co-doping. The BCSTZS ceramics sintered at 1550°C exhibit improved thermal stability of the piezoelectric and ferroelectric properties within the common usage temperatures, indicating that the BCSTZS ceramics are promising lead-free candidates for the widely used lead-based piezoelectric materials.

Structural and electrical characteristics of rhombohedral lead zirconate titanate single crystals

Two PbZr x Ti1−x O3 (PZT) single crystals, from a batch prepared by the flux method, were analysed to assess their chemical composition. The two single crystals were found by electron microprobe analysis to have the chemical compositions PbZr0.60Ti0.40O3 and PbZr0.65Ti0.35O3. X-ray diffraction at −93 °C revealed that both crystals have the R3m space group, which means that the R3m ↔ R3c phase transition is not observed in this composition range for temperatures above −93 °C. The dielectric permittivity was measured along the [001] direction at several frequencies from 1 kHz to 1 MHz, at varying temperatures up to 460 °C, and the parameters of the Curie–Weiss law were determined. The parameters of a thermodynamic model for the rhombohedral phase were determined by fitting the experimental data with the theoretical model. The polarization was calculated as function of the temperature for both crystals and the results were used to observe the order of the phase transition. The polarization increases when the concentration of PZT approaches the morphotropic region from the rhombohedral side. This fact, already observed in ceramic samples, is for the first time reported in single crystals which contributes for the clarification of the maximum of electrical properties in the morphotropic region.

Fabrication and characterization of binary piezoelectric (Bi1/2Na1/2)TiO3-Ba(Mn1/3Nb2/3)O3 solid solutions

High-density solid solutions with compositions of (1−x)(Bi1/2Na1/2)TiO3−xBa(Mn1/3Nb2/3)O3 (BNT-BMN), with x = 0 − 0.06, were prepared by using the conventional ceramic fabrication process. The optimal composition that yielded the best piezoelectric properties for high-power piezoelectric applications was investigated. X-ray diffraction (XRD) analyses of BNT-BMN with x = 0 − 0.06 suggested that the rhombohedral-pseudocubic morphotropic phase boundary (MPB) for this material system is in the compositional region 0.035 ≤ x ≤ 0.04 at room temperature. A hard-mode BNT-BMN with x = 0.03, which lay on the rhombohedral side near the MPB region, exhibited excellent piezo- and ferroelectric properties.

Effects of composition and temperature on the large-field behavior of [001]C relaxor single crystals.

The compositional dependence of the large-field behavior of [001]C-cut relaxor ferroelectric xPb(In1/2Nb1/2) O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 (PIN-PMN-PT) single crystals that are on the rhombohedral side of the morphotropic phase boundary was characterized under electrical, mechanical, and thermal loading. The effects of varying the concentrations of PIN and PT are discussed. Composition was found to impact the material constants and the field-induced phase transformation threshold in the piezoelectric d333-mode configuration.

The Impact of Heat Treatment on the Domain Configuration and Strain Behavior in Pb[Zr,Ti]O3 Ferroelectrics

The influence of heat treatment in lead zirconate titanate Pb(Zr,Ti)O3 (PZT) ferroelectrics on the domain structure and strain behavior has been investigated. Temperature-induced changes in the domain configuration, for example, appearance of nanodomains within microdomains, were observed by in situ hot-stage transmission electron microscopy. During the transient post annealing state the strain behavior under electric field differed from that of the nonheat-treated ferroelectrics. Directly after cooling the difference was most pronounced and decreased as a function of time. The enhanced response to an electric field of 4 kV/mm resulted in qualitatively different effects on strain for PZT from the tetragonal side and from the rhombohedral side of the morphotropic phase boundary.

Structures and Properties of Pb(Zr0.5Ti0.5)O3−Pb(Zn1/3Nb2/3)O3− Pb(Ni1/3Nb2/3)O3 Ceramics for Energy Harvesting Devices

Piezoelectric ceramics with large energy density coefficient d33·g33 value have been found suitable for piezoelectric energy harvesting applications. In this study, the phase structures and piezoelectric properties of xPb(Zr0.5Ti0.5)O3−yPb(Zn1/3Nb2/3)O3−(1−x−y)Pb(Ni1/3Nb2/3)O3 (xPZT−yPZN−(1−x−y)PNN) ceramic were investigated with systematically varying PZN and PNN components. The ternary phase diagram of PZT−PZN−PNN system was illustrated and the composition region of morphotropic phase boundary (MPB) was determined. Piezoelectric and dielectric measurements verify that the materials in MPB region all present large d33 and d33·g33 values. In particular, very high d33·g33 coefficients of 20162.2 × 10−15 m2/N and 21026.3 × 10−15 m2/N are observed from samples 0.75PZT−0.15PZN−0.1PNN and 0.8PZT−0.05PZN−0.15PNN with compositions located on the rhombohedral phase side near MPB because the dielectric coefficient ε33T/ε0 decreases faster than the d33 coefficient at this side.

Photoluminescence in Pb0.95Sr0.05(Zr1−xTix)1−yCryO3 ferroelectric ceramic system

Over the past several years, there has been a remarkable growth and development in new ceramic and/or composite materials to be used in the electro-electronic industry. Ferroelectric materials have been recognized for their multifunctional physical properties; also, their optical properties are a subject of intense research effort due to their possible electro-optic applications. In this work, the visible photoluminescence effect is analyzed at room temperature in a sintered Pb0.95Sr0.05(Zr1−xTix)1−yCryO3 perovskite-type structure system, doped with Sr and Cr. The excitation bands used were 267, 325, 373, 457, 635, and 680 nm, but the best result was obtained at 373 nm. The intensity and energy of such emission in this system have been studied by changing the molar Cr concentration (0 &amp;lt; y &amp;lt; 0.005) and the Ti content (x), with x = 0.20, 0.40, 0.53, 0.60, and 0.80, on both sides of the morphotropic phase boundary (MPB) zone. The principal emission bands are at the energies 1.73, 1.87, and 3.03 eV. The changes that were caused by Zr or Ti ions in the symmetry presented in the rhombohedral or tetragonal side of the MPB are more important. Additionally, structural and micro-structural measurements were performed by the x-ray diffraction and scanning electron microscopy techniques, respectively. The micro-Raman technique is also used in the study of this set of samples, which allows finding the Raman shift modes and the influence on the structural changes of the dopants.