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.     

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.     

Ferro-/pyroelectric response of 0.57BF-0.31PMN-0.12PT ternary ceramic far away from morphotropic phase boundaries

A ternary BiFeO₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (BF-PMN-PT) solid solution with a composition far away from morphotropic phase boundaries (MPB) has been synthesized by solid-state reaction method. XRD analysis revealed a pure perovskite phase without any trace of pyrochlore phase. The system exhibited a broad phase transition with transition temperature T_c ~ 285 °C. The hysteresis loop of the ceramics displayed high remanent polarization (Pr ~ 41.23 μC/cm²) and coercive field (E_c ~ 35.41 kV/cm). The true-remanent polarization after removing the non-remanent components was evaluated by remanent hysteresis and PUND tasks, which revealed the actual usable polarization component for memory devices. Time-dependent compensated plots confirmed the resistive-leakage free characteristic of the BF-PMN-PT ceramics which makes them useful for application in devices like actuators where the electric field is switched at different rates. Fatigue test showed the ferroelectric parameters (switching and non-switching polarization values) do not vary over 10⁷ cycles which is important especially in electromechanical transducers and memory devices. A large piezoelectric charge coefficient (d₃₃ ~ 115 pC/N) was observed for the investigated ceramics.     

Crystal structure and piezoelectric characteristics of various phases near the triple-point composition in PZ-PT-PNN system

Crystal structures and piezoelectric properties of PbZrO₃-PbTiO₃-Pb(Ni_1/3Nb_2/3)O₃ ceramics near the triple point composition, particularly characteristics of the pseudocubic phase, were investigated. The pseudocubic phase, which formed near the triple point composition, disappeared with increase in the PbZrO₃ content. The pseudocubic phase had the Pm3m cubic structure. The tetragonal-pseudocubic morphotropic phase boundary (MPB) structure was developed during the tetragonal-to-cubic phase transformation. However, the rhombohedral phase directly transformed to the cubic phase because the structure of pseudocubic phase was similar to the rhombohedral structure. The specimens with pseudocubic phase and the specimens near pseudocubic phase exhibited nano-sized domains and small coercive electric fields, revealing their low domain wall energies. These specimens exhibited second-order ferroelectric-to-paraelectric phase transition and low Curie temperatures, confirming their low domain wall energies. The enhanced dielectric and piezoelectric properties of these specimens could be attributed to their low domain wall energies.     

Temperature- and electric-field-dependent electrical properties and nanoscale domain structures in PIN-0.49PMN-0.27 PT single crystal

The effect of temperature and electric field on phase transitions, dielectric relaxation behavior, and macroscopic electrical performances of Pb(In_1/2Nb_1/2)O₃-0.49 Pb(Mg_1/3Nb_2/3)O₃-0.27PbTiO₃ (PIMNT27) single crystals were studied. The nanosized domains of unpoled crystals and the engineered domains of DC electric field poled crystals were intuitively recorded by piezoresponse force microscopy (PFM). The distribution of nanosized domains with different sizes and patterns induced by domain switching and domain wall motion under different poling fields and temperatures were also studied to understand the effect of nanosized domains on phase transitions, piezoelectric, and electromechanical properties.     

Domain switching and polarization fatigue in rhombohedral PIN-PMN-PT and Mn-doped PIN-PMN-PT single crystals

Domain switching process under alternating electric field was investigated by in situ polarized light microscopy in [001]-oriented Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) and Mn-doped PIN-PMN-PT single crystals. Only one-step 71° switching was confirmed in pure and Mn-doped PIN-PMN-PT crystals by the formed domain walls, whose projections on the (001) plane are along 45° or 135° with respect to [010] direction. Moreover, polarization and strain loops during cyclic electric field were studied in depth as a function of switching cycles. Polarization fatigue appeared obviously above 1000 bipolar cycles in PIN-PMN-PT samples, while Mn-doped PIN-PMN-PT samples exhibited almost fatigue-free characteristics. By considering the thermodynamic theory, the improved fatigue resistance in Mn-doped PIN-PMN-PT crystals stems from the enhanced energy barrier of domain switching. Mn modification does not affect the domain switching paths, but it can enhance the energy barrier of domain switching, leading to the improved fatigue behaviors. Our results provide a useful insight into the underlying mechanisms between the domain switching process and polarization fatigue for applying high-performance relaxor-ferroelectric single crystals.     

Templated grain growth of high coercive field CuO-doped textured PYN-PMN-PT ceramics

This paper explores the templated grain growth and texturing of Pb(Yb_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PYN-PMN-PT) ceramics. A PbO-CuO liquid phase was determined to substantially increase the growth of PYN-PMN-PT on barium titanate template particles. Texturing resulted in an 83% enhancement in strain behavior (754 pm/V) compared with random PYN-PMN-PT ceramics (413 pm/V). The increased Pb(Yb_1/2Nb_1/2)O₃ (PYN) content of textured 21PYN-41PMN-38PT resulted in a high coercive field of 13.9 kV/cm. Residual barium titanate templates reduced the polarization from 33.7 to 26.2 µC/cm² and slightly decreased the Curie temperature (236-224°C). These results show that textured PYN-PMN-PT is a promising material for high strain and coercive field transducers.     

Densification and properties of oxygen sintered CuO-doped PIN-PMN-PT ceramics

Relationships between sintering temperature and annealing atmosphere on microstructure and dielectric, ferroelectric, and piezoelectric properties of reactively sintered CuO-doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) ceramics were investigated. Uniform 2−3 μm grain size, dense CuO-doped PIN-PMN-PT ceramics are obtained when oxygen sintered versus a bimodal grain size microstructure when sintered in air. Oxygen sintered ceramics have excellent properties including d₃₃ = 300–315 pC/N, E_C = 7.7–8 kV/cm, and tan δ < 1.5%. The MPB region was mapped for ternary compositions doped with 0.5 mol% CuO and sintered in O₂. MPB 25PIN-40PMN-35PT demonstrated the maximum piezoelectric properties with d₃₃ = 565 +/− 23 pC/N and k_p = 0.64 +/− 0.01. Sintering from 1050 °C to 1200 °C increased the coercive field from 8.5 to 11.5 kV/cm and reduced dielectric losses from tan δ = 1.8% to 0.8% by facilitating diffusion of CuO into the lattice and creating domain wall pinning defect dipoles as evidenced by an increase in the internal field bias of P-E loops.     

Fabrication and characterization of (Pb(Mg1/3Nb2/3)O3, Pb(Yb1/2Nb1/2)O3, PbTiO3) ternary system ceramics

New ternary compositions in the Pb(Mg_1/3Nb_2/3)O₃-Pb(Yb_1/2Nb_1/2)O₃–PbTiO₃ (PMN-PYbN-PT) system were prepared using 0.5Pb(Yb_1/2Nb_1/2)O₃-0.5PbTiO₃ (PYbNT) and (1-x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ (x = 0.26; PMNT26 or x = 0.325; PMNT32.5) powders synthesized via the columbite method. Dense (≥ 96% of theoretical density) ceramics with PMN/PYbN mole ratios of 25/75 (R-25), 50/50 (R-50) and 75/25 (R-75T and R-75R) were fabricated by reactive sintering at 1000 °C for 4 h. Therefore, incorporation of PYbNT to PMNT successfully decreased sintering temperature of PMNT from 1200 °C-1250 °C to 1000 °C. Samples with higher density and perovskite ratio together with lower weight loss possessed higher dielectric and piezoelectric values in each composition. The R-75 samples had remanent polarization (P_r) values of 34-36 μC/cm² and piezoelectric charge coefficient (d₃₃) of 560 pC/N. The sharp phase transition PMNT as a function of temperature became broader or more diffuse with increasing PYbNT content. However, PYbNT addition to PMNT increased Curie temperature (T_c) from 183 °C (for PMNT32.5) to 220-242 °C (for R-75T and R-75R) to 336 °C (for R-25). Therefore, these ternary compositions can be tailored for various high temperature applications due to the relatively higher T_c with enhanced piezoelectric and dielectric properties as compared to PMNT.     

Anisotropic field induced phase transitions and negative electrocaloric effect in rhombohedral Mn doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

The electrocaloric effect (ECE) of Mn doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT:Mn) single crystals with particular emphasis on the impact of crystallographic orientations and phase transitions were investigated systematically. Orientation-dependent phase transitions have been demonstrated by the dielectric and strain behaviors. Intriguingly, the negative ECE of –0.02?°C and –0.002?°C were obtained firstly in [001]-oriented PIN-PMN-PT:Mn crystals near the rhombohedral→tetragonal phase transformation and in [011]-oriented crystals near the rhombohedral→orthorhombic phase transformation, respectively. However, only the positive ECE was found in [111]-oriented crystals near the tetragonal→rhombohedral phase transition. Additionally, the maximum ECE temperature changes calculated in [001]-, [011]- and [111]-oriented crystals were 0.33?°C, 0.46?°C and 0.38?°C, respectively. Our results suggest that the negative ECE is attributed to electric field-induced phase transitions, whose critical field decreases with the increase of temperature. The phase transition-mediated coexistence of positive and negative effects in the relaxor-ferroelectric single crystals is beneficial to enhance the efficiency of the solid-state cooling devices.     

Effect of PMN modification on structure and electrical response of xPMN–(1−x)PZT ceramic systems

The structural and electrical properties of xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr,Ti)O₃ ternary ceramic system with the composition near to the morphotropic phase boundary (MPB) and of xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr_0.47Ti_0.53)O₃ ceramics were investigated as a function of the Pb(Mg_1/3Nb_2/3)O₃ (PMN) content by scanning electron microscopy (SEM), X-ray diffraction (XRD), dielectric and piezoelectric spectroscopy and polarization-electric field measurement technique. Studies were performed on the samples prepared by a columbite precursor method for x=0.125, 0.25 and 0.5. Room temperature SEM investigations revealed common trends in the grain structure with increasing PMN content. XRD analysis demonstrated that with increasing PMN content in xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr_0.47Ti_0.53)O₃, the structural change occurred from the tetragonal to the pseudocubic phase at room temperature. Changes in the dielectric and ferroelectric behavior were then related to these structural trends and further correlated with the piezoelectric properties. The results of ferroelectric hysteresis measurements, in conjunction with dielectric spectroscopy, demonstrated an intermediate, relaxor-like behavior between normal and relaxor ferroelectrics in the solid solution system, depending on the PMN content.     

High electric field-induced strain properties in La-doped Pb(In1/2Nb1/2)O3–PbZrO3–PbTiO3 relaxor ferroelectric ceramics

Piezoelectric ceramics with high strain response and low hysteresis are highly in demand for high-performance actuator applications. Unfortunately, the trade-off relationship between large field-induced strain and low hysteresis in piezoelectric ceramics is a key challenge for designing high-performance piezoelectric actuators. Herein, ymol%La-doped 0.10 Pb(In_1/2Nb_1/2)O₃-xPbZrO₃-(0.90–x)PbTiO₃ [0.10PIN-xPZ-(0.90-x)PT: ymol%La] ternary relaxor ferroelectric ceramics were prepared by conventional solid-state reaction technique. Pb(In_1/2Nb_1/2)O₃ (PIN) as a relaxor end member was introduced into (Pb,La) (Zr,Ti)O₃ (PLZT) system to improve relaxor characteristics and strain properties. A giant strain of 0.23% was obtained in 0.10PIN-0.59PZ-0.31 PT: 8mol%La ceramic at the electric field of 20 kV/cm, with a high piezoelectric d₃₃* of 1150 pm/V and low hysteresis H_y of 6.4%, exhibiting a potential application in high-performance piezoelectric actuators. Furthermore, the effects of La ion doping and components on the ferroelectric, dielectric and electric field-induced strain properties were investigated, and provides a new way for improve the strain properties of piezoelectric materials.     

Structure and enhanced properties of perovskite ferroelectric PNN–PZN–PMN–PZ–PT ceramics by Ni and Mg doping

Perovskite ferroelectric oxide ceramics of 0.1Pb(Ni_1/3Nb_2/3)O₃–0.35Pb(Zn_1/3Nb_2/3)O₃–0.15Pb(Mg_1/3Nb_2/3)O₃–0.1PbZrO₃–0.3PbTiO₃ (0.10PNN–0.35PZN–0.15PMN–0.10PZ–0.30PT) with excess MgO and NiO were investigated in this work. The effects of the excess MgO and NiO doping on the ceramic structure, density, dielectric, ferroelectric and piezoelectric properties were studied. The chemical states of nickel were examined using X-ray photoelectron spectroscopy (XPS). Both XPS experimental results and theoretical analyses on the basis of ionic packing indicated that the excess valence-two ions substituted the A-sites in the ABO₃ perovskite structure. By completely eliminating the pyrochlore phase and enhancing densification with the excess NiO and MgO, improved piezoelectric coefficient d₃₃ up to 459 pC/N, higher ferroelectric remnant polarization and dielectric constant were demonstrated when sintered at temperature as low as 850–950 °C.     

A new multiferroic ternary solid solution system: NdFeO3–Pb(Fe1/2Nb1/2)O3–PbTiO3

Ceramic materials were sintered from powders of the NdFeO₃–Pb(Fe_1/2Nb_1/2)O₃–PbTiO₃ (NF–PFN–PT) ternary system synthesized by the conventional solid reaction method and their multiferroic properties investigated. The structure, electric and magnetic properties of the ternary system have been investigated. The introduction of Pb(Fe_1/2Nb_1/2)O₃ into the NdFeO₃–PbTiO₃ binary system can effectively increase its electric properties. The ternary system exhibits enhanced piezoelectric property with optimal piezoelectric constants d₃₃=143 pC/N, reduced coercive fields E_C=5.78 kV/cm and remnant polarization P_r=12.8 μC/cm² for 0.10NF–0.56PFN–0.34PT, near tetragonal phase region. The Curie temperature (T_C) of the NdFeO₃–Pb(Fe_1/2Nb_1/2)O₃–PbTiO₃ ceramics varies in the range from 108.7 °C to 67.9 °C. The magnetic hysteresis loops show that the ternary system is paramagnetic originating from canting of paramagnetic sublattices in NF–PFN–PT, due to the rare earth ions Nd³⁺ influencing on the exchange interaction between Fe³⁺ ions at the octahedral sites.     

Achieving high energy storage performance of Pb(Lu1/2Nb1/2)O3 antiferroelectric ceramics via equivalent A-site engineering

Manipulating the critical switching field between antiferroelectric (AFE) state and ferroelectric (FE) is an important concept for tuning the energy storage performance of AFEs. As one of the lead-based AFE systems, Pb(Lu_1/2Nb_1/2)O₃ promises high potential in the miniaturization of pulsed power capacitors, but the extremely high critical switching field and low induced saturated polarization demonstrate severe drawbacks with respect to temperature stability and flexibility. Here, A-site Ba²⁺ doping engineering is used to effectively reduce the critical switching field and improve the saturated polarization in Ba_xPb_1-x(Lu_1/2Nb_1/2)O₃ (0.01 ≤ x ≤ 0.08, abbreviated as xBa-PLN) ceramics. We found the AFE-FE phase transition can be occurred at 80ºC with a high energy storage density of 4.03 J/cm³ for Ba_0.06Pb_0.94(Lu_1/2Nb_1/2)O₃ ceramic. Our results show that Ba²⁺ additions destroy the antiparallel structure of AFE phase, and finally reduce the critical switching field, demonstrating a potential alternative to modulate the energy storage performance of AFEs.     

Evolution of polar nano-regions under electric field around ferro-paraelectric transition temperature and its contribution to piezoelectric property in Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 crystal

As one of the most pronounced structural features, polar nano-regions (PNRs) is believed to have significant contribution to the outstanding piezoelectric property of relaxor-based ferroelectrics. However, direct experimental investigation on the connection between the PNRs behavior under electric field and piezoelectric responses is still insufficient. In this work, by the combined use of piezoresponse force microscopy, polarization light microscopy, and the electrical property measurements, we investigate the structure evolution from macro-domains to PNRs around ferro-paraelectric phase transition temperature (T_m, 140?°C) in Pb(Mg_1/3Nb_2/3)O₃-0.30PbTiO₃ single crystal. Most importantly, based on the corresponding analysis of unipolar strain-electric-field (S-E) curves at different temperatures and the direct observation of electric-field-induced structure evolution at T_m, we intensively investigate the response of PNRs to electric field and its contribution to piezoelectric property. We conclude that, under electric field, the active PNRs around T_m first serve as polar seeds to induce macro-domains from the non-polar matrix, then promote the switching of macro-domains. The large-field strain coefficient d₃₃^* in these two processes can achieve maximum of about 5410?pm/V and 61710?pm/V at T_m, and gradually decreases at higher temperature with lower PNRs content.     

Crystal structure and electrical properties of textured Ba2Bi4Ti5O18 ceramics

Highly textured Ba₂Bi₄Ti₅O₁₈ ceramic was prepared by spark plasma sintering (SPS). X-ray diffraction of the ceramics revealed the coexistence of a major ferroelectric phase (Space group, SG: B2cb) and a minor paraelectric phase (SG: I4/mmm) at room temperature. A diffused phase transition was observed at around 240 °C. The evolution of the switching current peaks in the electric current vs. electric field (I-E) loops with increasing temperature was interpreted by the structural changes and temperature dependent polarisation reversal processes. The slim polarisation vs. electric field (P-E) loops, the extra switching current peaks in the I-E loops and the non-zero piezoelectric d₃₃ coefficient indicate that Ba₂Bi₄Ti₅O₁₈ is a relaxor ferroelectric material. The recoverable energy density (0.41 ± 0.01 J/cm³) of Ba₂Bi₄Ti₅O₁₈ ceramics in the perpendicular direction to the SPS pressing direction is close to that of Pb(Mg_1/3Nb_2/3)O₃-based ceramics. The obtained results suggest Ba₂Bi₄Ti₅O₁₈ ceramics might be promising for energy storage applications.     

Phase transition and energy storage properties of Bi0.5Na0.5TiO3–Bi(Mg2/3Nb1/3)O3 lead-free ceramics

Bi_0.5Na_0.5TiO₃ (BNT) lead-free ceramics have been extensively studied due to their excellent dielectric, piezoelectric and ferroelectric properties. The phase structure and functionalities of BNT can be feasibly adjusted by doping/forming solid solutions with other elements/components. In this work, Bi(Mg_2/3Nb_1/3)O₃ (BMN) was introduced into BNT by a conventional solid-state reaction to form a homogeneous solid solution of (1-x)(Bi_0.5Na_0.5)TiO₃-xBi(Mg_2/3Nb_1/3)O₃ (BNT-xBMN) with a perovskite structure. With the increase of BMN content, a phase transition from rhombohedral R3c to tetragonal P4bm has been confirmed by XRD, along with shifting the ferroelectric-paraelectric phase transition temperature to lower temperatures with broadening dielectric peaks. Furthermore, an optimized recoverable energy density of 1.405 J/cm³ was achieved for BNT-0.10BMN ceramics under a low applied electric field of 140 kV/cm, which is mainly attributed to the transformation from ferroelectric to ergodic relaxor phase.     

Large-strain 0.7Pb(ZrxTi1−x)O3–0.1Pb(Zn1/3Nb2/3)O3–0.2Pb(Ni1/3Nb2/3)O3 piezoelectric ceramics for high-temperature application

0.7Pb(Zr_xTi_1−x)O₃–0.1Pb(Zn_1/3Nb_2/3)O₃–0.2Pb(Ni_1/3Nb_2/3)O₃ (0.7PZT–0.1PZN–0.2PNN, x = 0.44–0.47) piezoelectric powders and ceramics have been prepared through conventional solid-state reaction method. Outstanding piezoelectric and dielectric properties occurred at the morphotropic phase boundary (MPB), which was characterized by the X-ray diffraction spectrum. The MPB composition (x = 0.46) performed high d₃₃ value (641 pC/N), indicating that the system suited large-strain application. The field-induced strain reached 0.25% under a considerably low electric field (0.8 kV/mm) according to the bipolar strain *S–E loops. The effect of the grain size on the aging phenomenon and temperature stability has also been investigated. Due to higher Curie temperature and smaller grain size, the 0.7PZT–0.1PZN–0.2PNN ceramics maintained a high d₃₃ level after depoling treatment, revealing a superior strain capacity for high-temperature application.