Investigation of dielectric and piezoelectric properties in Pb(Ni1/3Nb2/3)O3–PbHfO3–PbTiO3 ternary system

The dielectric and piezoelectric properties were investigated in the (1 ? x)Pb(Hf_1?yTi_y)O₃–xPb(Ni_1/3Nb_2/3)O₃ (PNN–PHT, x = 0.05–0.50, y = 0.55–0.70) ternary system. The morphotropic phase boundary (MPB) was determined by X-ray powder diffraction analysis. Isothermal map of Curie temperature (T_C) related to the compositions in the phase diagram was obtained. The optimum dielectric and piezoelectric properties were achieved in ceramics with the MPB compositions, with the maxima values being on the order of 6000 and 970pC/N, respectively. Rayleigh analysis was used to study the extrinsic contribution (domain wall motion) in PNN–PHT system, where the extrinsic contribution was found to be ～30% for composition 0.49PNN–0.51PHT(30/70), showing a high nonlinearity.     

Densification behavior and electrical properties of CuO-doped Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary ceramics

CuO modified Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PMN–PT) ternary relaxor based ferroelectrics with the composition near the morphotropic phase boundary were synthesized by two-step columbite precursor method. The introduction of CuO significantly improved the sinterability of PIN–PMN–PT ceramics, resulting in the full densification of samples at lower sintering temperatures. It also profoundly modified the crystal structure and fracture mode of the ceramics. Properly increasing CuO content led to the disappearance of rhombohedral-tetragonal phase transition, remarkably improved the Curie temperature (T_c), and made the ceramics more relaxorlike. The ternary ceramics doped with 0.25 wt% CuO possessed optimum piezoelectric properties (d₃₃=584 pC/N, d₃₃^*=948 pC/N, and k_p=0.68), high ferroelectric properties (E_c=9.9 kV/cm, and P_r=33.1 μC/cm²), low dielectric loss (tan δ=0.9%), and wider temperature usage range (T_c=225 °C). The obtained properties are much higher than those of previously reported PIN–PMN–PT based ceramics, indicating that CuO doped PIN–PMN–PT is a promising candidate for electromechanical applications with high performance and wide temperature/electric field usage ranges.     

Microstructure evolution and reaction mechanism of Pb(Zr1/2Ti1/2)O3-Pb(Zn1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3 piezoelectric ceramics with plate-like PbTiO3 template

0.83 Pb(Zr_1/2Ti_1/2)O₃-0.11Pb(Zn_1/3Nb_2/3)O₃-0.06Pb(Ni_1/3Nb_2/3)O₃ (PZNNT) samples with plate-like PbTiO₃ (PT) template were prepared using tape casting technology. The microstructure evolution and reaction mechanism between the matrix and PT template was investigated systematically. The quench heat treatment experiment was designed and the microstructure was evaluated. The results showed that the plate-like PT template has relatively low thermal stability which would decompose to form Pb-rich liquid phase and Ti-rich region at the sintering temperature of 900 °C–1050 °C. Plate-like PT template reacted with the PZNNT matrix materials during the sintering process, which did not contribute to the grain growth orientation for PZNNT matrix. Finally, the mechanism of grain growth for the PZNNT ceramics with plate-like PT template is clarified. This work demonstrated that the thermal stability of plate-like template is one of the key factors for fabricating textured piezoelectric ceramics.     

Preparation,structure, and electric properties of the Pb(Zn1/3Nb2/3)O3–Pb(Yb1/2Nb1/2)O3–PbTiO3 ternary ferroelectric system ceramics near the morphotropic phase boundary

Ceramics of the xPb(Zn_1/3Nb_2/3)O₃–(1 ? x ? y)Pb(Yb_1/2Nb_1/2)O₃–yPbTiO₃ (PZN–PYN–PT) ternary system were synthesized using a modified two-step columbite precursor method which can effectively suppress the pyrochlore phase. A morphotropic phase boundary (MPB) region, separating tetragonal and rhombohedral phases in the ternary systems has been determined. The electric properties of the compositions near MPB region were investigated. Dielectric response exhibits relaxor-like characteristics with broad dielectric peaks and dispersive dielectric behavior with respect to frequency and temperature. The phase diagram of the 0.45PZN–(0.55 ? y)PYN–yPT pseudo-binary system in the composition range of 0.15 < y < 0.35 was established based on dielectric measurements. The optimal properties were achieved in the MPB composition of 0.52PZN–0.21PYN–0.27PT with piezoelectric coefficient d₃₃, dielectric permittivity ε′, planar electromechanical coupling k_p, dielectric loss tan δ, coercive field E_c, remnant polarization P_r, and T_C being of 558 pC/N, 2065, 62%, 0.2%, 19.88 kV/cm, 31.44 μC/cm² and 259.5 °C, respectively, showing potential usage in high-temperature electromechanical applications.     

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.     

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.     

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.     

Crystal structure and piezoelectric properties of xPb(Mn1/3Nb2/3)O3–(0.2 − x)Pb(Zn1/3Nb2/3)O3–0.8Pb(Zr0.52Ti0.48)O3 ceramics

Pb(Mn_1/3Nb_2/3)O₃–Pb(Zn_1/3Nb_2/3)O₃–Pb(Zr_0.52Ti_0.48)O₃ (designated as PMnN–PZN–PZT) piezoelectric ceramics were prepared and the effects of PMnN content on the crystal structure and electrical properties were investigated. The results show that the pure perovskite phase forms in these ceramics. The crystal structure changes from tetragonal to rhombohedral and the lattice constant decreases with increase of PMnN content. The morphotropic phase boundary (MPB) of xPMnN–(0.2 ? x)PZN–0.8PZT ceramics occurs where the content of PMnN, x, lies between 0.05 and 0.085 mol. The dielectric constant (?), piezoelectric constant (d₃₃) and Curie temperature (T_c) decrease, while the mechanical quality factor (Q_m) increases with the increase of PMnN content. The ceramic with composition 0.075PMnN–0.125PZN–0.8PZT has the optimal piezoelectric properties, ? is 842, d₃₃ is 215 pC/N, T_c is 320 °C, k_p is 0.57 and Q_m amounts to 1020, which makes it a promising material for high power piezoelectric devices.     

Effect of compositional modifications on microstructure development and dielectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 solid solutions

The effect of minor additions of excess MgO and PbO on the sintering characteristics, microstructure development and dielectric properties of perovskite-based Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ solid solutions was investigated. Both MgO and PbO are compatible with the Pb(Mg_1/3Nb_2/3)O₃-based solid solutions and thus, these phases co-exist with one another during sintering at elevated temperatures. On sintering a solid solution composition Pb[(Mg_1/3Nb_2/3)_0.9Ti_0.1]O₃ with minor additions of MgO, the excess MgO remained as a discrete phase in the ceramics at temperatures up to 1230 °C and inhibited grain growth. Above this temperature, MgO combined with the solid solution to form a liquid phase, which caused an enhancement of the densification process. On sintering the solid solution with excess PbO, a low-temperature melting PbO-rich liquid phase was formed, which promoted the densification process with inhomogeneous grain growth. Simultaneous additions of 1.0 wt.% MgO and 2.0 wt.% PbO to the Pb[(Mg_1/3Nb_2/3)_0.9Ti_0.1]O₃ solid solution and sintering the resulting material at 1000 °C for 3 h led to the formation of a dense and homogeneous microstructure consisting of evenly distributed grains with an average grain size of 10 μm. The peak dielectric constant of this composition (at ≈38 °C), measured at a frequency of 1 kHz, was 18,000 with a dissipation factor of <2%.     

Relaxation behavior in 0.24Pb(In1/2Nb1/2)O3–0.49Pb(Mg1/3Nb2/3)O3–0.27PbTiO3 ferroelectric single crystal

Dielectric relaxation properties of the ternary relaxor-based ferroelectric 0.24Pb(In_1/2Nb_1/2)O₃–0.49Pb(Mg_1/3Nb_2/3)O₃–0.27PbTiO₃ single crystal have been investigated as a function of temperature (300–570 K) in the frequency range from 100 Hz to 100 kHz. It was found that the variation of the permittivity maximum temperature T_m with frequency obeys the Vogel–Fulcher relationship. The high-temperature (T>T_m) side of the dielectric permittivity deviated from the Curie–Weiss law, but can be described by the Lorenz-type relationship. The coercive field obtained from the polarization hysteresis loops gradually decreases with increasing temperature, and the remnant polarization persists above T_m due to the existence of polar nanoregions (PNRs).     

Electrocaloric properties of 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 ceramics with different grain sizes

We have investigated the electrocaloric (EC) properties of the ceramic 0.7Pb(Mg_1/3Nb_2/3)O₃–0.3PbTiO₃. A variety of samples with different median grain sizes, i.e., 1.0, 2.2 and 4.0?μm, and relative densities of about 96% were prepared using atmospheric sintering at 1200^oC for 2, 8 and 16?h. The ceramic material with a median grain size of 2.2?μm exhibited the highest value for the EC temperature change, i.e., 1.27?K at 60?kV?cm^?1, measured with a high-resolution calorimeter. This value is 25 and 19% higher than the value for the ceramics with the finer and the coarser grains, respectively.     

A new Pb(Lu1/2Nb1/2)O3–PbZrO3–PbTiO3 ternary solid solution with morphotropic region and high Curie temperature

A ceramic ternary system of (1?x?y)Pb(Lu_1/2Nb_1/2)O₃–xPbZrO₃–yPbTiO₃ (PLuN–PZ–PT) has been prepared by two-step synthetic process and characterized by X-ray powder diffraction and electric measurements. A morphotropic phase boundary (MPB) region has been delimited in the ternary system at room temperature. With the PLuN content increasing, the morphotropic phase boundary region becomes broad as well as the dielectric peak. The best comprehensive piezoelectric properties were achieved at MPB composition 0.42PLuN–0.1PZ–0.48PT, with the piezoelectric coefficients d₃₃, the Curie temperature T_c, the planar electromechanical coupling factor K_p, and the remnant polarizations P_r being 367 pC/N, 360 °С, 68% and 35 μС/cm², respectively. The results indicate that the PLuN–PZ–PT ternary ferroelectric material may be a promising candidate for high-power electromechanical transducers that can operate in a large temperature range.     

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.     

Electrical properties of Sb and Cr-doped PbZrO3–PbTiO3–PbMg1/3Nb2/3O3 ceramics

The pyroelectric, dielectric and DC resistive properties of Sb and Cr-doped ceramics with a base composition of Pb(Mg_1/3Nb_2/3)_0.025(Zr_0.825Ti_0.175)_0.975O₃ have been studied. Sb doping has been shown to produce a linear reduction in Curie temperature (T_C=−22z+294 °C) with concentration (z) and to give an increase in pyroelectric coefficient from 250 to 310 μCm⁻² K⁻¹ for z increasing from 0 to 3 at.%. It also produces first a reduction and then an increase in both dielectric constant and loss, so that the 33 Hz pyroelectric figures of merit (FOM's) are as follows: F_V peaks at 3.8×10⁻² m² C⁻¹ and F_D peaks at 1.2×10⁻⁵ Pa^−1/2. The resistivity is increased substantially from 1.1×10¹¹ to ca 6×10¹¹ Ωm with 1 at.% Sb, thereafter changing little. The behaviour has been explained in terms of Sb acting as a donor ion, reducing oxygen vacancy concentrations up to 1 at.%, with conductivity dominated by hole hopping between traps (E_a=0.59±0.05 eV) that are not changed by the Sb doping. It is concluded that additions of higher levels of Sb do not produce electron-mediated hopping conduction. The Cr additions have no effect upon T_C, but reduce dielectric constant and loss, pyroelectric coefficient and resistivity at doping levels up to 3 at.%. The FOM F_V peaks at 3.6×10⁻² m² C⁻¹ and F_D at 1.9×10⁻⁵ Pa^−1/2. The behaviour of the electrical resistivity as a function of dopant level is shown to produce a linear ln(σ_o) vs z^−1/3 dependence (σ_o=DC conductivity), as would be expected for hole hopping conduction between Cr³⁺ sites, with an E_a=0.38±0.03 eV.     

Determining the effects of BaTiO3 template alignment on template grain growth of Pb(Mg1/3Nb2/3)O3 –PbTiO3 and effects on piezoelectric properties

Crystallographic texturing of ferroelectric ceramics is an established method of inducing single crystal-like properties in a ceramic material via epitaxial grain growth according to the template used, otherwise known as Templated Grain Growth (TGG). The piezoelectric enhancement is dependent on the degree of TGG throughout the ceramic, which is closely linked to the tape casting parameters and sintering conditions. Pb(Mg1/3Nb2/3)O₃-PbTiO₃ (PMN-PT) perovskite ferroelectrics with morphotropic phase boundary compositions using 3 vol% BaTiO₃ templates were used for analysis. The blade gap and template size have the greatest impact on the overall grain alignment. The varying degrees of template alignment is related to the different enhancements of TGG and the correlating piezoelectric d₃₃ and d*₃₃. The highest piezoelectric property was demonstrated in PMN-31PT with Lotgering factor of 93% where d₃₃ = 1020 pC/N and d*₃₃ = 1420 pm/V were achieved.     

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.     

Domain structure and evolution in ZnO-modified Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 ceramics

The doping of ZnO is efficient to improve the piezoelectric property and thermal stability of Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PMN–PT) based ceramics. However, the underlying physics, especially the local domain structures of the ZnO modified PMN–PT ceramics, which is strongly associated with the electric properties, is not clear yet. In this paper, we investigated the local domain structures and their evolution as a function of x in PMN–0.32PT:xZnO ceramics. It was found that, the domain evolution is mainly caused by the growth of grain size induced by the sintering aiding effect of ZnO at x < 0.04, and the domain evolution can be attributed to the phase transition induced by the partial replacement of Mg²⁺ by Zn²⁺ in the B-site of PMN–PT lattice at x > 0.06. Furthermore, we also investigated the domain structure evolution as functions of temperature and local external electric field in PMN–0.32PT:0.06ZnO ceramics, which exhibited superior piezoelectric property relative to other compositions. We found that the irregular nanodomains are more stable at high-temperature range, and the regular non-180° domains exhibited more complex rotation behavior under local electric field, which probably leads to the thermal stability and piezoelectric property enhancement in the ZnO-modified PMN–0.32PT ceramics.     

Linear thermal expansion coefficients of relaxor-ferroelectric 0.57Pb(Sc1/2Nb1/2)O3–0.43PbTiO3 ceramics in a wide temperature range

The objective of this work was to examine linear thermal expansion of virgin and poled 0.57Pb(Sc_1/2Nb_1/2)O₃–0.43PbTiO₃ ceramics between 30 °C and 600 °C by contact dilatometry. The thermal expansion dL/Lo of the virgin ceramic increases with increasing temperature until approximately 260 °C. The physical and technical thermal expansion coefficients were determined. At 260 °C the physical thermal coefficient is 2.08 × 10^?6 K^?1. Between 260.0 °C and 280.0 °C an anomaly in the thermal expansion vs. temperature and an endothermic peak in the differential scanning calorimetry curves correspond to the phase transition region from tetragonal to cubic phase. At temperatures from 280 °C to 600 °C the thermal expansion dL/Lo increases again.In the derivative of the dL/Lo heating curves of the poled ceramics, additionally to the anomaly at 270 °C, also the anomaly at 160 °C is observed, which is associated with the depolarization of the material during heating.