Characterization of domain structure and imprint of Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-4.5%PT) single crystals by using PFM and SS-PFM techniques

In this study, the underlying physical mechanisms of imprint are addressed in order to obtain a better understanding of the imprint phenomenon of relaxor Pb(Zn_1/3Nb_2/3)O₃-x%PbTiO₃ (PZN-x%PT) ferroelectric single crystals. The local domain structure and imprint of Pb(Zn_1/3Nb_2/3)O₃-4.5%PbTiO₃ (PZN-4.5%PT) single crystals are investigated by using Piezoresponse Force Microscopy (PFM) and Switching Spectroscopy PFM (SS-PFM) techniques, respectively. The results show that the imprint depends on polarization states. It is also found that surface charge accumulation shows no significant effects on the imprint behaviour of the PZN-4.5%PT single crystals. By studying the annealed samples in the oxygen and argon atmospheres respectively, it is found that the alignment of oxygen vacancy related defect dipoles is one of the origins for the occurrence of imprint. This study provides a better understanding of the imprint phenomenon in ferroelectric materials, which is crucial for the enhancement of the reliability and the advancement of ferroelectric relaxors into the application of ferroelectric devices.     

Dieletric and relaxation behaviors of (PbMg1/3Nb2/3O3)0.67(PbTiO3)0.33 single crystal

Dielectric permittivity along the [111] direction has been measured as a function of temperature for a relaxor ferroelectric single crystal (PbMg_1/3Nb_2/3O₃)_0.67(PbTiO₃)_0.33 (PMN-33%PT). A sharp ferroelectric phase transition was observed near 425 K and 429 K for cooling and heating processes, respectively. As temperature decreases, a diffuse phase transition (which begins near 330 K upon cooling) was detected. In addition, the nature of the thermal hysteresis for the dielectric permittivity confirms that these transitions (near 330 and 425 K upon cooling) are diffuse first-order and first-order, respectively. The frequency-dependent dielectric data ε'₁₁₁ (ƒ, T) prove the existence of an electric dipolar relaxation process between 350 and 400 K. The activation energy, the Vogel-Fulcher temperature and attempt frequency corresponding to this relaxation process are also calculated.     

Anisotropic domain switching in Pb(Mg1/3Nb2/3)O3‐0.30PbTiO3 single crystals with rhombohedral structure

Anisotropic domain switching paths in [001]‐, [011]‐, and [111]‐poled Pb(Mg_1/3Nb_2/3)O₃‐0.30PbTiO₃ single crystals were studied by in situ polarized light microscopic driven by an antiparallel electric field. Orientation‐dependent electric field induced polarization and strain behaviors were investigated systematically. For [001]‐oriented crystals, only one‐step 71° switching occurred during the domain switching process, resulting in the appearance of stripe domain walls whose traces on (001) plane were along 45° or 135° with respect to [100] direction. But for [011]‐oriented samples, a two‐step 71° switching was observed during 109° switching and the projections of formed twin domain walls on the (011) plane are along 35.3° or 144.7° with respect to [01] direction. Moreover, a three‐step 71° switching was found during 180° switching in [111]‐oriented samples. It was demonstrated by the produced domain walls whose projections on the (10) plane are along 35.3°, 90° or 160.6° with respect to [11] direction. The energetically motivated mechanism based on multistep polarization switching process was also proposed to explain the anisotropic domain switching paths. Our results provided a visualized observation on the ferroelectric domain switching process and also laid the solid foundations for controlling polarization order parameter in ferroelectric single crystals.     

Temperature- and frequency-dependent hysteresis scaling behaviour and phase transitions in a [001]c 0.73Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystal

The dielectric properties and bipolar polarization-electric field (P-E) and strain-electric field (S-E) dynamic hysteresis of a relaxor [001]_c 0.73Pb(Mg_1/3Nb_2/3)O₃-0.27PbTiO₃ (PMN-0.27PT) single crystal were investigated to reveal more details of the temperature-induced phase transitions. Different linear scaling relations for ferroelectric hysteresis area <A>, coercive field E_c, saturation polarization P_s and remnant polarization P_r versus temperature τ were measured in different temperature regions. For each measurement frequency f, all hysteresis parameters were found to decrease linearly with temperature in the temperature range of the single rhombohedral (R) phase or tetragonal (T) phase, and the rate of decrease in the T phase was observed to be much larger than the corresponding rate in the R phase. In the temperature range near the R-T phase transition, the exponent α in the power law <A>∝f ^α for the R phase was found to be smaller than that for the T phase, and the magnitude of α depended strongly on temperature when the crystal was in the R-T coexisting phase state. Our experimental and theoretical results indicate that the difference in the activation energy and dipole moment in the R and T phases may lead to the observed discrepancy for the P-E and S-E hysteresis behaviour in different temperature regions.     

Anisotropic domain structures of Pb(Mg1/3Nb2/3)O3–PbZrO3–PbTiO3 single crystals with high ferroelectric phase transition temperature

The anisotropic domain structures and local piezoresponse of rhombohedral Pb(Mg_1/3Nb_2/3)O₃–PbZrO₃–PbTiO₃ single crystals with high ferroelectric phase transition temperature (T_FE‐FE≥120°C) were systematically investigated by vector piezoresponse force microscopy. The typical size of labyrinthine domain pattern for [001]_C sample was in the range of 100‐200 nm, revealing its relaxor feature. While the [011]_C sample exhibited ordered ribbon‐shaped domain pattern with preferential alignment along <011> direction since the modulation effect of polar nanoregions. For [111]_C sample, it had messy and featureless domain patterns. For as‐grown crystal, the incorporation of Zr⁴⁺ cation in Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ system resulted in that the long‐range coulomb interactions of the charged ions in the short range order regions were weakened, leading to an increased relaxor feature. Concurrently, the incorporation of Zr⁴⁺ cation enhanced the Pb‐B repulsion intensity, resulting in an improved T_FE‐FE. Temperature‐dependent properties of as‐grown crystal exhibited good temperature stability from 30 to 120°C, indicating it is a promising material for actuator and ultrasonic transducer applications.     

Multi-step domain switching and polarization fatigue in [110]-oriented 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystals

Domain switching in ferroelectrics is at the heart of many functionalities, and the visualization of switching pathway is the key to understand the fundamental properties and to promote the applications of high-performance ferroelectrics. Here, we directly documented the multi-step domain switching in [110]-oriented 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-0.33PT) single crystals under a cycling electric field with the help of in situ polarized light microscopy. Based on the characteristic domain configuration analysis, we demonstrated that the 180° switching process was consisted of multi-step 60° switching. Such a multi-step 60° switching pathway resulted in a large negative strain and an internal electric field, which contributes to a large polarization fatigue rate under the alternating electric field. Our works may provide a window to study the domain switching process and its effect on polarization fatigue in relaxor-ferroelectric single crystals.     

Fabrication of 0.24Pb(In1/2Nb1/2)O3-0.42Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 transparent ceramics by conventional sintering technique

0.24Pb(In_1/2Nb_1/2)O₃-0.42Pb(Mg_1/3Nb_2/3)O₃-0.34PbTiO₃ transparent ceramics were fabricated by a conventional sintering technique. Through optimization of sintering conditions of calcination and sintering temperatures and time, the obtained ceramics showed high optical transmittance of 53% and 71% at light wavelengths of 1300 and 2000 nm, respectively. The ceramics showed a rhombohedral to tetragonal phase transition at ~120°C and a tetragonal to cubic phase transition at 222°C. These transition temperatures were higher than those of 0.67Pb(Mg_1/3Nb_2/3)-0.33PbTiO₃ ceramics. In addition, the ceramics had a ferroelectric hysteresis loop, a large piezoelectric constant d₃₃ of 407 pC/N, and a planar electromechanical coupling factor k_p of 52%. These results suggest that the transparent ceramics may be used as a temperature-stable, linear electro-optic material.     

Growth and characterization of large size lead-free ferroelectric K(Ta,Nb)O3 single crystal

Lead-free piezoelectric materials with excellent performance are greatly demanded for the environmental issues. The lead-free ferroelectric single crystals are therefore greatly concerned for their much higher piezoelectricity than the polycrystalline counterparts and the domain-tunable property. However, the growth of large size and high-quality lead-free ferroelectric crystals has always been a great challenge. In this work, a ferroelectric KTa_1-xNb_xO₃ (KTN) single crystal with an extremely large size of 25 × 25 × 37 mm³ was grown using the modified top-seeded solution growth method. The large size enabled us to carry out comprehensive investigations on the crystal. The complete sets of dielectric, piezoelectric, and elastic constants for the [001]_C-poled KTN crystal with quasi single domain state were determined. Results showed that the crystal exhibits high electromechanical coupling coefficients with k_t~0.642 and k₃₃~0.679. Furthermore, the orientation dependence of the piezoelectric, dielectric, and elastic properties was determined by the tensor matrix transformation technique, and the maximum d₃₃, , and k₃₃ were found along the polar direction [001]_C. This work not only provides important guidance for the growth technology of lead-free ferroelectric crystals but also offers essential datasets of lead-free alkali niobate system, which is of great importance for both theoretical studies and designs of electromechanical devices.     

Structural and Electrical Characteristics of (1−x)Pb(Lu1/2Nb1/2)O3–xPbTiO3 Ceramics with Low PbTiO3

A solid solution of (1?x)Pb(Lu_1/2Nb_1/2)O₃–xPbTiO₃ with composition of 0.01 ≤ x ≤ 0.08 have been prepared successfully. XRD analysis indicates the crystal structure adopts an orthorhombic (O) phase in 0.01 ≤ x ≤ 0.06 interval and becomes the coexistence of O and rhombohedral (R) phase at x = 0.07, then turns into R phase mostly at x = 0.08. In addition, two sets of superlattice reflections due to B‐site ordering and antiparallel cation displacement are distinguished by XRD and the superstructures which arise from antiparallel cation displacement disappear gradually with the increasing x. The grain size increases gradually with the increasing x, and then becomes the bimodal microstructure at x ≥ 0.06 due to the coexistence of O and R phase. The dielectric spectra exhibit Curie temperature decreases from 248°C to 147°C with increasing x from 0.01 to 0.08. As 0.01 ≤ x ≤ 0.04, the samples display typical double hysteresis loops, suggesting antiferroelectric nature, then turn into ferroelectric gradually at x = 0.05. Finally, it exhibit typical ferroelectric hysteresis loops in 0.06 ≤ x ≤ 0.08 interval.     

Achieving single domain in rhombohedral and tetragonal Mn-doped Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)-PbTiO3 crystals for infrared detecting applications

The [111]-oriented rhombohedral Mn-doped 0.15Pb(In_1/2Nb_1/2)-0.55Pb(Mg_1/3Nb_2/3)O₃-0.30PbTiO₃ (Mn:PIMNT(15/55/30)) crystal and the [001]-oriented tetragonal Mn-doped 0.29Pb(In_1/2Nb_1/2)-0.29Pb(Mg_1/3Nb_2/3)O₃-0.42PbTiO₃ (Mn:PIMNT(29/29/42)) crystal were poled under different conditions. The pyroelectric performance of the two crystals as a function of poling temperature, as well as the relationship with ferroelectric domain configuration and phase structure was investigated systematically. The pyroelectric properties of the two crystals enhance with rising the poling temperature, which can be attributed to the improvement of the single state. And for the rhombohedral Mn:PIMNT(15/55/30) crystal locating near morphotropic phase boundary (MPB), the increase of tetragonal phase induces the deterioration of pyroelectric properties. Due to more residual tetragonal phase, the pyroelectric coefficient of the Mn:PIMNT(15/55/30) crystal poled at 150°C is lower than that poled at 100°C. In general, both the crystals poled above T_C achieve nearly single state, exhibiting the best pyroelectric properties with relatively high Curie temperature (T_C), where P = 9.71 × 10⁻⁴ C m⁻² K⁻¹, F_i = 3.88 × 10⁻¹⁰ m V⁻¹, F_v = 0.068 m² C⁻¹ and F_d = 29.7 × 10⁻⁵ Pa^−1/2 for the rhombohedral Mn:PIMNT(15/55/30) crystal (T_C = 171°C) and P = 6.78 × 10⁻⁴ C m⁻² K⁻¹, F_i = 2.71 ×10⁻¹⁰ mV⁻¹, F_v = 0.1 m² C⁻¹, F_d = 23.54 × 10⁻⁵ Pa^−1/2 for the tetragonal Mn:PIMNT(29/29/42) single crystal (T_C = 251°C), meeting the stable operation of infrared detector at relatively high environmental temperatures.     

Lead-reduced Bi(Ni2/3Ta1/3)O3-PbTiO3 perovskite ceramics with high Curie temperature and performance

With increasing demand of high-temperature piezoelectric devices and growing concern over environment protection, a feasible reduction in lead from lead-based high Curie temperature piezoelectric materials are desperately needed. Herein, a new system of lead-reduced Bi(Ni_2/3Ta_1/3)O₃-PbTiO₃ (BNT-PT) ferroelectric ceramics is fabricated by a conventional solid-state sintering process. The phase transition behaviors as a function of composition and temperature, electrical properties, as well as the domain configurations from a microscopic level have been investigated in detail. The results indicate that crystal structures, phase transition behaviors, and electric properties of BNT-PT ceramics can be affected significantly by the content of BNT counterpart. Dielectric measurements show that xBNT-(1−x)PT ceramics transfer from the normal ferroelectrics to the relaxor ferroelectrics at compositions of x = 0.3-0.35. The BNT-PT ceramics exhibit high Curie temperature T_C ranging from 474 to 185°C with the variation in BNT content. The relative dielectric tunability n_r also rises from only 0.65% for 0.10BNT-0.90PT to 50.23% for 0.40BNT-0.60PT with increasing BNT content. The tetragonal-rich composition 0.30BNT-0.70PT ceramic possesses the maximum remnant polarization of P_r ~ 34.9 μC/cm². Meanwhile, a highest piezoelectric coefficient of d₃₃ ~ 271 pC/N and a high field piezoelectric strain coefficient of  ~ 560 pm/V are achieved at morphotropic phase boundary (MPB) composition of 0.38BNT-0.62PT. The maximum value of strain ~0.31% is obtained in the 0.36BNT-0.64PT ceramic. The largest electromechanical coupling coefficient k_p is 44.5% for 0.37BNT-0.63PT ceramic. These findings demonstrate that BNT-PT ceramics are a system of high-performance Pb-reduced ferro/piezoelectrics, which will be very promising materials for piezoelectric devices. This study offers an approach to developing and exploring new lead-reduced ferroelectric ceramics with high performances.     

Large electrocaloric strength in the (100)-oriented relaxor ferroelectric Pb[(Ni1/3Nb2/3)0.6Ti0.4]O3 single crystal at near morphotropic phase boundary

Relaxor ferroelectric Pb[(Ni_1/3Nb_2/3)_0.6Ti_0.4]O₃ (PNNT) single crystal with composition close to the morphotropic phase boundary (MPB) was successfully prepared using the molten salt method. The analysis results of XRD and TEM indicated that the as-grown crystal is of almost pure perovskite phase with coexistence of tetragonal and rhombohedral. Typical relaxor behavior was observed when the crystal was aged. Large electrocaloric strength (ΔT/ΔE) of 44.97 mK cm/kV was obtained near the phase transition temperature of paraelectric to ferroelectric, indicating that PNNT is a promising material for application in cooling system. Moreover, it is found that the aging of point defects may make an important contribution to the electrocaloric performance of the single crystal, in addition to the contribution of the transition of phases induced by the electric field.     

Phase distribution and corresponding piezoelectric responses in a morphotropic phase boundary Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal revealed by confocal Raman spectroscopy and piezo-response force microscopy

Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-xPT) single crystals exhibit ultrahigh piezoelectric property and have already been applied in various industrial fields. Here, spatial distribution of coexistent phases and corresponding local piezoelectric responses in a morphotropic phase boundary (MPB) PMN-xPT single crystal are thoroughly investigated by confocal Raman spectroscopy coupled with piezo-response force microscopy (PFM). Different from previous studies on MPB crystals, spatial distribution of coexistent phases is exhibited intuitively in an image obtained by confocal Raman mapping. Via in-situ PFM measurements, domain morphology of each coexistent phase is observed. Moreover, local piezoelectric responses of each coexistent phase are obtained by switching spectroscopy PFM measurements, indicating that Ma and Mc phases behave like PNRs and polar matrix in PMN-xPT crystals Our work clarifies the contribution from different phases to the giant piezoelectric performance, which can deepen the understanding on the ultrahigh piezoelectricity in PMN-xPT crystals and provide the key point for developing novel high piezoelectricity materials.     

Electric properties of polycrystalline PbCd1/3Nb2/3O3

Temperature dependence of dielectric permittivity and electric conductivity of polycrystalline PbCd_1/3Nb_2/3O₃ in the region of phase transition have been presented. Electric properties of polycrystalline PbCd_1/3Nb_2/3O₃ depend on frequency of the measuring field. In the region of para-ferroelectric phase transition a change of electric properties takes place.     

Temperature-dependent phase transition in [001]C-oriented 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystals

Temperature-dependent dielectricity and polarization of [001]_C-oriented 0.72Pb(Mg_1/3Nb_2/3)O₃-0.28PbTiO₃ relaxor-based ferroelectric single crystals were studied by using a combined method of the X-ray diffraction, dielectric spectrum, polarization-electric (P-E) field hysteresis loops, and the Landau-phenomenological theory. Results show that the room-temperature rhombohedral phase experiences a rhombohedral-monoclinic-tetragonal coexisting state, then transforms to tetragonal phase, and finally to cubic phase during the zero-field-heating process. The six-order Landau-type thermal expansion parameters for the tetragonal phase were determined by using the typical characteristics at the cubic-tetragonal phase transition in the temperature range from 91 °C to 113 °C. The calculated dielectric curve, polarizations, and P-E loops fit well with the experimental results. The phase stability and piezoelectricity are further studied and compared with those of the PMN-0.36PT single crystal. The provided methods and obtained Landau parameters can be used for further studies on the relaxor-based ferroelectric single crystals.     

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.     

High rhombohedral to tetragonal phase transition temperature and electromechanical response in Pb(Yb1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 ferroelectric system near the morphotropic phase boundary

Relaxor-PT crystals, that is, Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) and Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT), have been used in mechanical to electric energy translation devices, such as for high-frequency imaging and underwater detection. However, low temperature usage remains a problem for high temperature applications, which are restricted by rhombohedral to tetragonal phase temperatures (T _R-T). In this work, we synthesized a new xPb(Yb_1/2Nb_1/2)O₃-yPb(Sc_1/2Nb_1/2)O₃-0.37PbTiO₃ (x = 0.2?0.45) (xPYN-yPSN-0.37 P T) ternary piezoelectric polycrystalline with high T _R-T = 225?245 °C. For 0.45PYN-0.18PSN-0.37 P T ceramics, the piezoelectric coefficient d₃₃, mechanical coupling factors k₃₃, k_p, and k_t, and dielectric coefficients ε_r and T _R-T are on the order of 330 pm/V, 68.3%, 54.3%, 49.3%, 930, and 245 °C, respectively. Thermal piezoelectric and ferroelectric behaviors were investigated in 0.45PYN-0.18PSN-0.37 P T polycrystalline, which are good candidates for high temperature piezoelectric application. DSC curves for xPYN-yPSN-0.37 P T systems present two peaks at 1213 and 1291 °C during the cooling process, showing good crystallization behavior and suitability for single crystal growth.