Domain Reengineering of the [011]‐Poled PMN–0.35PT Single Crystals for Dielectric Bolometer Arrays

The domain configuration was reengineered with a modified poling procedure for the [011]‐poled single‐domain PMN–0.35PT crystals located at the morphotropic phase boundary. As a consequence, the dielectric constant ε_r at room temperature was significantly enhanced by more than 10 times to about 18 000, extremely higher than the reported (1 ? x)Pb(Mg_1/3Nb_2/3)O₃‐xPbTiO₃ ferroelectric crystals. Besides, the decreasing rate of the dielectric constant (dε_r/dT) was about 300/K with a temperature coefficient (α) of 1.7%/K, comparable to the BST materials for dielectric bolometer applications. The ferroelectric phase transition behavior was investigated to establish the poling procedure and a thermal hysteresis of about 25°C was indicated across the room temperature for the orthorhombic–tetragonal phase transition, which contributed to the revolution of the domain pattern.     

Preparation and characterization of Pb(Lu1/2Nb1/2)O3–Pb(In1/2Nb1/2)O3–PbTiO3 ternary ferroelectric ceramics with high phase transition temperatures

To explore new relaxor‐PbTiO₃ systems for high‐power and high‐temperature electromechanical applications, a ternary ferroelectric ceramic system of Pb(Lu_1/2Nb_1/2)O₃–Pb(In_1/2Nb_1/2)O₃–PbTiO₃ (PLN–PIN–PT) have been investigated. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the as‐prepared PLN–PIN–PT ceramics near the morphotropic phase boundary (MPB) were characterized. A high rhombohedral‐tetragonal phase transition temperature T_R‐T of 165°C and a high Curie temperature T_C of 345°C, together with a good piezoelectric coefficient d₃₃ of 420 pC/N, were obtained in 0.38PLN–0.20PIN–0.42PT ceramics. Furthermore, for (0.8?x)PLN–0.2PIN–xPT ceramics, the temperature‐dependent piezoelectric coefficients, coercive fields and electric‐field‐induced strains were further studied. At 175°C, their coercive fields were found to be above 9.5 kV/cm, which is higher than that of PMN–PT and soft P5H ceramics at room temperature, indicating PLN–PIN–PT ceramics to be one of the promising candidates in piezoelectric applications under high‐driven fields. The results presented here could benefit the development of relaxor‐PbTiO₃ with enhanced phase transition temperatures and coercive fields.     

Phase Diagram and Properties of High TC/TR−T Pb(In1/2Nb1/2) O3–Pb(Zn1/3Nb2/3)O3–PbTiO3 Ferroelectric Ceramics

A ternary ferroelectric ceramic system, (1?x?y)Pb(In_1/2Nb_1/2)O₃–xPb(Zn_1/3Nb_2/3)O₃–yPbTiO₃ (PIN–PZN–PT, x = 0.21, 0.27, 0.36, 0.42), was prepared using a two‐step precursor method. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the ternary ceramics were systematically investigated. A morphotropic phase boundary (MPB) was identified by X‐ray diffraction. The optimum piezoelectric and electromechanical properties were achieved for a composition close to MPB (0.5PIN–0.21PZN–0.29PT), where the piezoelectric coefficient d₃₃, planar electromechanical coupling factor k_p, and remnant polarization P_r are 660 pC/N,72%, and 45 μC/cm², respectively. The Curie temperature T_C and rhombohedral to tetragonal phase transition temperature T_R?T were also derived by temperature dependence of dielectric measurements. The strongly “bended” MPB in the PIN–PT system was found to be “flattened” after addition of PZN in the PIN–PT–PZN system. The results demonstrate a possibility of growing ferroelectric single crystals with high electromechanical properties and expanded range of application temperature.     

Structural and electrical properties of ZnO-modified (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 ceramics with wide MPB regions

Ferro-/piezoelectric ceramics with high performances are generally found at the morphotropic phase boundary (MPB), where two or more different ferroelectric phases coexist. However, the MPB region is usually very narrow; for example, that of (1−x)Pb(Mg_1/3Nb_2/3)O₃−xPbTiO₃ (PMN-xPT) locates between x = 0.30−0.34. Herein, we report that ZnO-modified PMN-xPT polycrystalline ceramics have dramatically broadened MPB regions from x = 0.28, with rhombohedral and monoclinic coexisting phases, to x = 0.36, with tetragonal and monoclinic coexisting phases, as confirmed by powder X-ray diffraction and piezoresponse force microcopy measurements. The wide MPB region is attributed to lattice distortion caused by the substitution of Zn for Mg cations. As a result, the ceramics show composition insensitive electrical properties over wide composition ranges; for example, the piezoelectric coefficient (d₃₃) and electromechanical coupling factor (k_p) remain at near constant values of 450 pC/N and 0.5, respectively, in the range from x = 0.28−0.34. This work not only provides a robust and feasible method to broaden the MPB region but also offers some novel insights into promoting fundamental research on high-performance piezoelectric ceramics.     

The Effect of Electric Poling on the Performance of Lead‐Free (1−x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 Piezoceramics

The effect of increasing poling fields on the properties of (1?x)BZT–xBCT compositions across the morphotropic phase boundary (MPB) is studied using large signal polarization and strain, small signal permittivity and piezoelectric coefficient, and XRD measurements. Successive poling causes charge carrier migration inducing an internal bias field, which becomes large with respect to the coercive field resulting in biased ferroelectric and ferroelastic switching. Improvements in piezoelectric coefficient of 9% are significantly smaller in the tetragonal 60BCT composition compared with the improvement of approximately 50% in the rhombohedral 40BCT and MPB 50BCT compositions. While the properties continue to change with increased poling fields, the remnant ferroelastic domain texture parallel to the field direction, as observed from XRD, stays approximately constant. The improvement in overall domain alignment leading to largely enhanced intrinsic piezoelectricity originates from the alignment of 180° domains and possibly non‐180° domains in grains with orientations inclined to the electric field. As a result, poling is most effective in BZT–BCT materials that have low coercive fields, show low distortions and possess more polarization orientations, such as compositions in the rhombohedral phase field or near the MPB.     

Large Piezoelectric Response and Polarization in Relaxor Ferroelectric PbTiO3–Bi(Ni1/2Zr1/2)O3

New binary system (1?x) PbTiO₃?xBi(Ni_1/2Zr_1/2)O₃ (PT–100x BNZ) with x ≤ 0.45 were synthesized via solid‐state reaction route. A morphotropic phase boundary (MPB) was identified around x = 0.40 by X‐ray diffraction (XRD) method. The ceramics with MPB composition exhibit enhanced ferroelectric properties. A large piezoelectric coefficient (d₃₃) up to 400 pC/N was obtained for the PT–40BNZ, which is comparable with the PbTiO₃–BiScO₃ (PT–BS, 450 pC/N).The frequency dependence of dielectric permittivity of PT–40BNZ shows characteristic of a strong relaxor feature and a transition temperature around 290°C (1 MHz). Temperature effect on the unipolar strain was also investigated. The present system with high d₃₃ is a competitive piezoelectric material, as no expensive oxide is used here compared with the PT–BS.     

Multi-scale domain structure observation and piezoelectric responses for [001]-oriented PMN-33PT single crystal

Multiple phase coexistence contributes to the extraordinary piezoelectric behavior of (1-x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ (PMN–xPT) near the morphotropic phase boundaries (MPBs). By incorporating an optical path of crossed polarized light (PLM) into the commercialized Piezoelectric Force Microscope (PFM) (named as PLM-PFM system), in situ domain structure observation from micro- to nanoscale, as well as measurement of the piezoelectric behavior for individual domains can be realized. For [001]-oriented single crystal of 67Pb(Mg_1/3Nb_2/3)O₃-33PbTiO₃ (PMN-33PT), fine domain boundary structures of rhombohedral (R), tetragonal (T), and monoclinic (M) phases are revealed. Measurements of the electric field-induced displacement as a function of the applied DC electric field (V_DC) are performed for domains with different polarization vectors. Values for the electric field-induced displacement are in descending order for c-domains of the M, R, and T phases. For an individual phase of T or M, the displacement increases when the angle between the polarization vector and the applied electric field decreases. The multi-scale perspective of the domain structures and the corresponding piezoelectric response helps in understanding the ultra-high piezoelectric performance for PMN-PT single crystals near MPB.     

Effects of Octahedral Tilting on the Piezoelectric Properties of Strontium/Barium/Niobium-Doped Soft Lead Zirconate Titanate Ceramics

(Pb_1−x−ySr_xBa_y)(Zr_0.976−zTi_zNb_0.024)O₃ solid solutions have been investigated to understand the relationship between structural changes caused by isovalent strontium and barium substitution on the A-site and dielectric and piezoelectric properties. As strontium and barium were substituted for lead, the zirconium:titanium (Zr:Ti) ratio was modified so that all compositions had an optimized piezoelectric coefficient (d₃₃). The value of d₃₃ was at a maximum in the tetragonal phase near, but not at, the morphotropic-phase boundary (MPB). The real MPB was taken as the Zr:Ti ratio at which X-ray diffraction patterns appeared either pseudocubic or a mixture of rhombohedral and tetragonal. As strontium content increased, optimized d₃₃ also increased from 410 pC/N (x= 0) to 640 pC/N (x= 0.12), commensurate with a decrease in the paraelectric-to-ferroelectric phase transition temperature (T_C) from 350°C (x= 0) to 175°C (x= 0.12). However, for ceramics where x > 0.12, optimized d₃₃ decreased even though the phase-transition temperature was ∼150°C. Low strontium concentration ceramics (x= 0–0.08) contained 80 nm ferrroelectric domains typical of PZT, but high strontium concentration ceramics (x= 0.12–0.16) contained fine-scale domains (20 nm) in some regions of the microstructure. In addition, [110] pseudocubic electron diffraction patterns revealed superlattice reflections at 1/2{hkl} positions associated with rotations of the octahedra in antiphase. Co-doping ceramics with strontium (x= 0.06) and barium (y= 0.06) resulted in the disappearance of the 1/2{hkl} reflections. Optimized d₃₃ (∼520 pC/N, T_C∼ 205°C) for this composition was similar to that of ceramics where x= 0.08, y= 0, which had a T_C of ∼250°C.     

Improvement of temperature-stability and piezoelectric performance of Pb(In0.5Nb0.5)O3–PbTiO3 crystals via Nd doping

High-performance relaxor-PbTiO₃ ferroelectric crystals have been widely applied in transduces, sensors and so on. The ferroelectric phase transition temperature restricts their application in automobile, deep oil-well detection and aerospace which requires high thermal stability. Decreasing the effects of ferroelectric phase transition is a promising strategy for improving the thermal stability. Here, the design strategy is structural regulation via rare earth doping tetragonal Pb(In_1/2Nb_1/2)O₃–PbTiO₃ (PIN-PT) crystals. The d₃₃, k₃₃ and T_C of [001]_c-oriented Nd-PIN-PT crystals are 750 pC/N, 87%, 250 °C. Compared with the d₃₃ of tetragonal 0.61PIN-0.39 PT crystals (540 pC/N) and tetragonal 0.35PIN-0.26 Pb(Mg_1/3Nb_2/3)O₃ (PMN)-0.39 PT crystals (530 pC/N), the d₃₃ of Nd-PINT crystals enhance by 39% and 41%. In addition, Nd-PIN-PT crystals have Q_m of 110, which is larger than rhombohedral relaxor-PbTiO₃ ferroelectric crystals (~50). Although the d₃₃ of Nd-PIN-PT crystals is lower than that of rhombohedral relaxor-PT ferroelectric crystals, the d₃₃ and k₃₃ are stable up to 250 °C, which is higher than tetragonal PIN-PMN-PT crystals (210 °C). The high thermal stability of piezoelectric properties is related to the high thermal stability of domain after poling. This work provides a design strategy for high thermal stability ferroelectric crystals.     

Normal‐Relaxor‐Diffuse Ferroelectric Phase Transition and Electrical Properties of Bi(Mg1/2Ti1/2)3–PbZrO3–PbTiO3 Solid Solution Ceramics Near the Morphotropic Phase Boundary

Perovskite‐type xBi(Mg_1/2Ti_1/2)O₃–(0.56 ? x)PbZrO₃–0.44PbTiO₃ (xBMT–PZ–PT) ternary solid solution ceramics were synthesized via a conventional solid‐state reaction method. The phase transition behaviors, dielectric, ferroelectric, and piezoelectric properties were investigated as a function of the BMT content. The X‐ray diffraction analysis showed that the tetragonality of xBMT–PZ–PT was enhanced with increasing the BMT content, and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases was identified approximately in the composition of x = 0.08. In addition, the dielectric diffuseness and frequency dispersion behavior were induced with the addition of BMT and a normal‐relaxor‐diffuse ferroelectric transformation was observed from the PZ‐rich side to the BMT‐rich side. The electrical properties of xBMT–PZ–PT ceramics exhibit obviously compositional dependence. The x = 0.08 composition not only possessed the optimum properties with ε^T₃₃/ε₀ = 1450, Q_m = 69, d₃₃ = 390 pC/N, k_p = 0.46, P_r = 30 μC/cm², E_c = 1.4 kV/mm, T_c = 325°C, and a strain of 0.174% (d₃₃^* = 436 pm/V) under an electric field of 4 kV/mm as a result of the coexistence of two ferroelectric phases near the MPB, but also owned a good thermal‐depolarization behavior with a d₃₃ value of >315 pC/N up to 290°C and a frequency‐insensitive strain behavior.     

Low‐temperature sintering and enhanced piezoelectric properties of random and textured PIN–PMN–PT ceramics with Li2CO3

Low‐temperature sintered random and textured 36PIN–30PMN–34PT piezoelectric ceramics were successfully synthesized at a temperature as low as 950°C using Li₂CO₃ as sintering aids. The effects of Li₂CO₃ addition on microstructure, dielectric, ferroelectric, and piezoelectric properties in 36PIN–30PMN–34PT ternary system were systematically investigated. The results showed that the grain size of the specimens increased with the addition of sintering aids. The optimum properties for the random samples were obtained at 0.5 wt% Li₂CO₃ addition, with piezoelectric constant d₃₃ of 450 pC/N, planar electromechanical coupling coefficient k_p of 49%, peak permittivity ε_max of 25 612, remanent polarization P_r of 36.3 μC/cm². Moreover, the low‐temperature‐sintered textured samples at 0.5 wt% Li₂CO₃ addition exhibited a higher piezoelectric constant d₃₃ of 560 pC/N. These results indicated that the low‐temperature‐sintered 36PIN–30PMN–34PT piezoelectric ceramics were very promising candidates for the multilayer piezoelectric applications.     

Structure‐property relationships in BiScO3–PbTiO3–PbMg1/3Nb2/3O3 ceramics near the morphotropic phase boundary

The phase structure, dielectric, ferroelectric, and piezoelectric properties of (1?2x)BiScO₃–xPbTiO₃–xPbMg_1/3Nb_2/3O₃ ceramics (x = 0.30‐0.46) were studied. It was found that an increase in x leads to a structural phase transition between the rhombohedral and tetragonal phase via an intermediate monoclinic phase and to a crossover from the nonergodic relaxor state to the ferroelectric one. It was proposed that at x > 0.42 the phase transition changes from second to first order. The assumption about the existence of a tricritical point on the phase diagram at x ≈ 0.42 with the enhanced dielectric response has been made. The observed structure‐property relationships of the studied solid solutions are discussed. It is shown that the solid solutions with x = 0.42 are characterized by the high piezoelectric parameters (d₃₃ = 509 pC/N, d₃₁ = ?178 pC/N, d_h = 153 pC/N), which makes possible their applications in sonar equipment.     

The Charge Release and Its Mechanism for Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 Ferroelectric Crystals Under One‐Dimensional Shock Wave Compression

The charge release and related mechanisms for Pb(In_1/2Nb_1/2)–Pb(Mg_1/3Nb_2/3)–PbTiO₃ (PIN–PMN–PT) ferroelectric crystals under one‐dimensional shock wave compression were investigated using discharge current profile measurement, by which the piezoelectric stress coefficient e₃₁ and the phase transition (from tetragonal to orthorhombic phase) pressure were obtained, being ?2.9 C/m² and 2.3 GPa, respectively. Based on experiment results and thermodynamics analysis, it was found that the one‐dimensional shock compression favored ferroelectric phase, being different from the effect of hydrostatic pressure, which favored paraelectric phase. This phenomenon can be attributed to the crystal anisotropy and electromechanical coupling effects as one‐dimensional shock compression is applied to PIN–PMN–PT ferroelectric crystals.     

High temperature‐insensitive ferro‐/piezoelectric properties and nanodomain structures of Pb(In1/2Nb1/2)O3–PbZrO3–Pb(Mg1/3Nb2/3)O3–PbTiO3 relaxor single crystals

For rhombohedral (R) Pb(In_1/2Nb_1/2)O₃–PbZrO₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PZ–PMN–PT) relaxor single crystal, high temperature‐insensitive behaviors under different external stimuli were observed (remnant polarization P_r from 30°C to 180°C and piezoelectric strain d₃₃* from 30°C to 116°C). When electric field E ≥ 50 kV/cm in the case of an activation field E_a = 40‐50 kV/cm was applied, it was found that the domain switching was accompanied by a phase transition. The high relaxor nature of the R phase PIN–PZ–PMN–PT was speculated to account for the large E_a and high piezoelectric response. The short‐range correlation lengths extracted from the out‐of‐plane (OP) and in‐plane (IP) nanodomain images, were 64 nm and 89 nm, respectively, which proved the high relaxor nature due to In³⁺ and Zr⁴⁺ ions entering the B‐site in the ABO₃‐lattice and enhancing the disorder of B‐site cations in the R phase PIN–PZ–PMN–PT. The switching process of R nanodomain variants under the step‐increased tip DC voltage was visually revealed. Moreover, the time‐dependent domain evolution confirmed the high relaxor nature of the R phase PIN–PZ–PMN–PT single crystal.     

Enhanced piezoelectric properties and electrocaloric effect in novel lead‐free (Bi0.5K0.5)TiO3‐La(Mg0.5Ti0.5)O3 ceramics

The crystal structure, electromechanical properties, and electrocaloric effect (ECE) in novel lead‐free (Bi_0.5K_0.5)TiO₃‐La(Mg_0.5Ti_0.5)O₃ ceramics were investigated. A morphotropic phase boundary (MPB) between the tetragonal and pseudocubic phase was found at x = 0.01‐0.02. In addition, the relaxor properties were enhanced with increasing the La(Mg_0.5Ti_0.5)O₃ content. In situ high‐temperature X‐ray diffraction patterns and Raman spectra were characterized to elucidate the phase transition behavior. The enhanced ECE (ΔT = 1.19 K) and piezoelectric coefficient (d₃₃ = 103 pC/N) were obtained for x = 0.01 at room temperature. Meanwhile, the temperature stability of the ECE was considered to be related to the high depolarization temperature and relaxor characteristics of the Bi_0.5K_0.5TiO₃‐based ceramics. The above results suggest that the piezoelectric and ECE properties can be simultaneously enhanced by establishing an MPB. These results also demonstrate the great potential of the studied systems for solid‐state cooling applications and piezoelectric‐based devices.     

Properties and structures of nonstoichiometric (K,Na)NbO3‐based lead‐free ceramics

The 0.968[(K_0.48Na_0.52)]Nb_0.95+xSb_0.05O₃–0.032(Bi_0.5Na_0.5)ZrO₃ [KNN_xS–BNZ] lead‐free ceramics with nonstoichiometric niobium ion were fabricated via conventional solid‐state sintering technique and their piezoelectric, dielectric and ferroelectric properties were investigated. When x = 0.010, enhanced piezoelectric properties (d₃₃ ≈ 421 pC/N and k_p ≈ 0.47) were obtained due to the construction of rhombohendral—tetragonal phase boundary near room temperature. The KNN_xS–BNZ ceramics possesses enhanced Curie temperature (T_c) with improved piezoelectric constant. A large d₃₃ of ~421 pC/N and a high T_c ~256°C can be simultaneously induced in the ceramics with x = 0.010. Especially, good thermal stability was observed in a broad temperature range. The results indicated that our work could benefit development of KNN‐based ceramics and widen their application range.     

Synthesis,structure and dielectric properties of (1−x)[0.9BiFeO3–0.1DyFeO3]–xPbTiO3 pseudo-binary ceramics

In order to develop multiferroics with large magnetization and polarization, we have prepared a series of (1?x)[0.9BiFeO₃–0.1DyFeO₃]–xPbTiO₃ [BDF–xPT] solid solution ceramics by solid state reaction. X-ray diffraction reveals that, with the increase of PbTiO₃ concentration, the solid solution transforms from a rhombohedral to a tetragonal phase with the presence of a morphotropic phase boundary (MPB) region located at 0.28≤x≤0.40 at room temperature, in which the rhombohedral, tetragonal and orthorhombic phases coexist. The temperature dependence of the dielectric permittivity indicates that the Curie temperature decreases with the increasing amount of PbTiO₃. Based upon the structural analysis and dielectric characterization, a preliminary phase diagram for the BDF?xPT pseudo-binary system has been proposed. It is found that the ceramics of compositions around the MPB exhibits much better dielectric properties with dielectric constant of the BDF–0.37PT ceramics reaching 459 at 1 kHz, confirming the beneficial effects of the MPB on the dielectric performance.     

Investigations on electric properties and domain structures of Nd-doped 0.70Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 relaxor ferroelectric ceramics with high piezoelectric properties

Although rare earth neodymium (Nd) doping is common in Pb(Mg1/3Nb2/3)O₃–PbTiO₃ (PMN–PT) single crystals, it is rarely reported in PMN–PT ceramics. To explore the effect of Nd doping on PMN–PT ceramics, PMN–30PT:xNd³⁺ (x = 0%, 1%, 2%, and 3%) relaxor ferroelectric ceramics were fabricated using a solid-state method via two-step sintering. An enhanced piezoelectric charge coefficient (d₃₃) of ∼870 pC/N and a high piezoelectric strain coefficient (d₃₃*) of ∼1025 pm/V were achieved for x = 2%. Through Rayleigh analysis of polarization–electric field (P–E) hysteresis loops under small electric fields, it was found that the dielectric property was mainly influenced by the intrinsic contribution (local lattice distortion). Furthermore, by investigating domain configurations, high piezoelectric properties were found to be associated with the domain size reduction and local structural heterogeneity. The results indicate that the PMN–30PT:xNd³⁺ ceramics is a promising material for electronic devices, and that rare earth Nd doping is an efficient strategy for improving the electronic performance of Pb-based relaxor ferroelectrics.     

Synthesis and Electrical Properties of New Lead‐free (100−x)(Li0.12Na0.88)NbO3–xBaTiO3 (0 ≤ x ≤ 40) Piezoelectric Ceramics

New lead‐free (100?x)Li_0.12Na_0.88NbO₃‐xBaTiO₃ (0 ≤ x ≤ 40) piezoelectric ceramics have been synthesized using conventional ceramics processing route. Structural analysis revealed an existence of morphotropic phase boundary (MPB), separating orthorhombic and tetragonal phases, between the BaTiO₃ content, x = 10–12.5. A partial phase diagram has been established based on temperature‐dependent permittivity data for this new system and a almost vertical temperature‐independent MPB is observed. Improvement in electrical properties near MPB (e.g., for x = 12.5; ε_r = 8842 at T_m and 795 at room temperature, d₃₃ = 30 pC/N, k_p = 12.0%, Q_m = 162, P_r = 11.2 μC/cm², E_c = 19.2 kV/cm, = 174 pm/V) is observed, and is attributed to the ease of polarization rotation due to coexistence of orthorhombic and tetragonal phases. The results show that these materials could be suitable for piezoelectric vibrators and ultrasonic transducer applications. The sample with x = 25, also exhibited high dielectric permittivity, ε_r = 2400, and low dielectric loss, tanδ = 0.033 at room temperature which could be suitable for capacitor (X7R/Z5U) applications.