Composition design,phase transitions and electrical properties of Sr2+-substituted xPZN–0.1PNN–(0.9−x)PZT piezoelectric ceramics

The influences of PZN content and Sr²⁺ substitution on the structure and electrical properties of Pb(Zn_1/3Nb_2/3)O₃–Pb(Ni_1/3Nb_2/3)O₃–Pb(Zr_0.52Ti_0.48)O₃ (abbreviated as PZN–PNN–PZT) piezoelectric ceramics were studied. All as-prepared PZN–PNN–PZT ceramics presented single phase of perovskite structure, while higher PZN contents favored rhombohedral symmetry and larger grain size. Meanwhile, with the increase in Sr²⁺ content, the phase structure changed from a mix of tetragonal and rhombohedral symmetries to a pure rhombohedral symmetry. Although the ferroelectric Curie temperature (T_C) was decreased with increasing the PZN and Sr²⁺ contents, the piezoelectric constant (d₃₃) exhibited the opposite trend. As a result, optimum comprehensive electrical properties were obtained in the 0.1PZN–0.1PNN–0.8PZT composition with 10 mol% Sr²⁺ substitution: d₃₃~800 pC/N, k_p ~0.65, ɛ_r~4081, T_C~176 °C, P_r~30.92 µC/cm². Thus, the 10 mol% Sr²⁺-substituted 0.1PZN–0.1PNN–0.8PZT ceramic is a promising candidate for high performance applications.     

Structure and electrical properties of PZT–PMS–PZN piezoelectric ceramics

The quaternary piezoelectric ceramics of Pb(Zr_0.52Ti_0.48)O₃–Pb(Mn_1/3Sb_2/3)O₃–Pb(Zn_1/3Nb_2/3)O₃ (PZT–PMS–PZN) with different PZN contents were synthesized by molten salt synthesis (MSS). The influence of PZN content on phase structure, microstructure, dielectric and piezoelectric properties was investigated in detail. The results of X-ray diffraction (XRD) show that the phase structure of ceramics transforms from rhombohedral phase to tetragonal phase with the increasing of PZN content. The morphotropic phase boundary (MPB) of composition is located in the range of PZN content from 2 to 7 mol%. The grain size of the ceramics gradually decreases with the increasing of PZN content. Dielectric and piezoelectric properties of ceramics are significantly influenced by the PZN content. Ceramics sintered at 1150 °C with 5 mol% PZN achieve excellent properties, which are as follows: Q_m = 1381, K_p = 0.64, d₃₃ = 369pC/N, tan δ = 0.0044 and T_c = 275 °C. The PZT–PMS–PZN system is a promising material for high power piezoelectric transformers application.     

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.     

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(Zr_0.5Ti_0.5)O₃?yPb(Zn_1/3Nb_2/3)O₃?(1?x?y)Pb(Ni_1/3Nb_2/3)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 ε₃₃^T/ε₀ decreases faster than the d₃₃ coefficient at this side.     

Phase-formation,microstructure, and piezoelectric/dielectric properties of BiYO3-doped Pb(Zr0.53Ti0.47)O3 for piezoelectric energy harvesting devices

This paper proposes a method for the composition and synthesis of lead zirconate titanate (PZT) piezoelectric ceramic for use in energy harvesting systems. The proposed material consists of (1?x)Pb(Zr_0.53Ti_0.47)O₃–xBiYO₃ [PZT–BY(x)] (x=0, 0.01, 0.02, 0.03, 0.04, and 0.05 mol) ceramics near the morphotropic phase boundary (MPB) region, prepared by a solid-state mixed-oxide method. The optimum sintering temperature was found to be 1160 °C, which produced high relative density for all specimens (96% of the theoretical density). Second phases were found to precipitate in the composition containing x≥0.01 mol of BY. It is shown that the addition of BY inhibits grain growth, and exhibits a denser and finer microstructure than those in the un-doped state. Fracture surface observation revealed predominant intergranular fracture for x=0 and x=0.01, while a mixed mode of transgranular and intergranular fracture appeared for x≥0.02. The optimal doping level was found to be x=0.01, for which a dielectric constant (K₃₃^T) of 750, a Curie temperature (T_C) of 373 °C, a remnant polarization (P_r) of 50 µC/cm², a piezoelectric constant (d₃₃) of 350 pC/N, and an electro-mechanical coupling factor (k_p) of 65% were obtained. In addition, the piezoelectric voltage constant (g₃₃), and transduction coefficient (d₃₃×g₃₃) of PZT–BY(x) ceramics have been calculated. The ceramic PZT–BY(0.01) shows a considerably lower K₃₃^T value, but higher d₃₃ and k_p. Therefore, the maximum transduction coefficient (d₃₃×g₃₃) of 18,549×10^?15 m²/N was obtained for PZT–BY(0.01). The large (d₃₃×g₃₃) indicates that the PZT–BY(0.01) ceramic is a good candidate material for energy harvesting devices.     

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.     

Effect of tungsten on the structure and piezoelectric properties of PZN–PZT ceramics

0.2PZN–0.8PZT ceramics with pure perovskite structure were prepared by the two-step method with the addition of 0–1.5 wt.% WO₃ and their piezoelectric properties were investigated. The WO₃ addition influences the lattice structure and W⁶⁺ will replace B-site ions of perovskite, which will lead to the decrease of the lattice constant. Compared to the increase of the dielectric constant (ɛ) and mechanical quality factor (Q_m), the values of coercive electric field (E_c), remnant polarization (P_r), electromechanical coupling factor (K_p), and piezoelectric constant (d₃₃) decrease with increasing WO₃ addition. The composition with 1.0 wt.% of WO₃ addition on 0.2PZN–0.8PZT ceramics exhibits excellent piezoelectric properties, showing great promise as practical materials for high power piezoelectric devices.     

Submicron crystalline buildup and size‐dependent energy harvesting characteristic in PZN–PZT ternary ferroelectrics

Piezoelectric energy harvester converts low‐frequency vibrational energy in the environment into electrical energy, enabling the purpose of self‐supplying power for low‐energy consumption devices. The key to miniaturizing energy harvester is the buildup of the submicron‐grained ceramic with a high transduction coefficient (d×g), which is still a big challenge from a technical point of view. In this work, the popular ternary system of Pb(Zn_1/3Nb_2/3)O₃–Pb(Zr_0.5Ti_0.5)O₃ (PZN–PZT) has been selected as objective compound, and the submicron‐grained ceramics were prepared by a combination of high‐energy ball milling and pressureless sintering technology. The results revealed that nanocrystalline PZN–PZT powders can be synthesized by one step mechanochemical route without the calcination stage. Using these nanopowders as precursors, dense ceramics with different grain size have been prepared through tailoring the sintering temperature. The study of size‐dependent energy harvesting characteristic evidenced an optimum transduction coefficient of 7980×10^?15 m²/N was obtained for 950°C sintered specimen, which has uniform microstructure with mean grain size of 0.33 μm. In the mode of the cantilever‐type energy harvester constructed by this material, the output power at low frequency of 89 Hz was as high as 69 μW at an acceleration of 10 m/s², showing the suitability for piezoelectric generators harvesting environmental vibrational energy.     

High power density in a piezoelectric energy harvesting ceramic by optimizing the sintering temperature of nanocrystalline powders

Piezoelectric energy harvesting is the research hotspot in the field of new energy, and its core is to prepare piezoelectric ceramics with high transduction coefficient (d₃₃ × g₃₃) and large mechanical quality factor (Q_m) as well. In addition, the miniaturization of the piezoelectric energy harvester also requires the material to have a submicron fine grain structure. In this work, submicron-structured ternary system, MnO₂-doped Pb(Zn_1/3Nb_2/3)O₃-Pb(Zr_0.5Ti_0.5)O₃ was constructed by pressureless sintering of nanocrystalline powders, which has been synthesized for the first time by high-energy ball milling route thereby evading the calcination stage. The microstructure and the energy harvesting characteristics were tailored through changing the sintering temperature. It was found that 1000 °C sintered fine-grained specimen (mean grain size ∼0.95 μm) showed the maximum d₃₃ × g₃₃ value of 9627 × 10⁻¹⁵ m²/N, meanwhile Q_m was as large as 774, which was almost seven times larger than pure counterpart. In the mode of the cantilever-type energy harvester, a high power density of 1.5 μW/mm³ were obtained for 1000 °C sintered specimen at a low resonance frequency of 90 Hz and acceleration of 10 m/s², which were further increased to 29.2 μW/mm³ when the acceleration increased to 50 m/s², showing the potential applications as a next generation high power multilayer energy harvester.     

Vibration energy harvesting with a clamped piezoelectric circular diaphragm

With the rapid development of low power devices, the technology of energy harvesting has improved greatly. The performance of a PZT diaphragm energy harvester is demonstrated in this paper. Under an acceleration of 9.8 m/s², a pre-stress of 1.2 N applied on the harvester, a power of 12 mW was generated at the resonance frequency of the harvester (113 Hz) across a 33 k ohm resistor. It was found that the energy from the harvester increases while its resonance frequency decreases when the pre-stress increasing. The contacting part between the proof mass and the piezoelectric disc was found another key element, which would influence the performance of the harvester. With its simple structure, the diaphragm harvester may push energy harvesting devices towards practical applications.     

Shift of morphotropic phase boundary in high-performance fine-grained PZN–PZT ceramics

The fine-grained xPb(Zn_1/3Nb_2/3)O₃–(1 − x)Pb(Zr_0.47Ti_0.53)O₃ system has been prepared from submicron precursor powders obtained by high-energy ball milling method. The addition of PZN induces a decrease of grain size from an initial micron scale to a submicron scale, accompanying with the phase transition from tetragonal to morphotropic phase boundary (MPB), and then rhombohedral side. Interestingly, compared to the former published data for coarse-grained ceramic, the MPB has shifted from 50% to 30% PZN content side due to the enhancement of the internal stress for fine-grained ceramic. The enhanced electrical and mechanical performances are closely associated with the phase structure and grain size. A high piezoelectric property (d₃₃ = 380 pC/N and k_p = 0.49) as well as mechanical performance (H_v = 5.0 GPa and K_IC = 1.33 MPa m^1/2) were obtained simultaneously for the MPB 0.3PZN–0.7PZT ceramics with an average grain size of 0.65 μm.     

(K,Na)NbO3-based ceramics with excess alkali oxide for piezoelectric energy harvester

(K_0.44Na_0.52Li_0.04)(Nb_0.86Ta_0.1Sb_0.04)O₃ (KNLNTS) ceramics were prepared by a solid-state reaction. The effect of excess (K,Na)₂O alkali oxide on the densification, phase evolution, microstructure development, and piezoelectric properties was investigated. The figure of merit (FOM) (d₃₃·g₃₃) for piezoelectric energy harvesting applications was also compared between the samples with and without excess alkali oxide. The addition of the excess alkali oxide changed the tetragonal crystal structure to orthorhombic and decreased the sintering temperature by about 100 °C. The dielectric constant of the orthorhombic phase is much lower than that of the tetragonal phase. The orthorhombic sample with excess alkali oxide sintered at 1020 °C demonstrated higher FOM in spite of having a smaller piezoelectric constant (d₃₃) than the stoichiometric sample sintered at 1100 °C. This result indicates that a KNN ceramic with an orthorhombic composition near the MPB with a moderate piezoelectric constant and smaller permittivity is more advantageous for an energy harvesting application than that with a morphotropic phase boundary (MPB) or a tetragonal composition.     

Relation between piezoelectric properties of ceramics and output power density of energy harvester

(1?x)Pb(Zr_0.47Ti_0.53)O₃–xPb[(Zn_0.4Ni_0.6)_1/3Nb_2/3]O₃ [(1?x)PZT–xP(ZN)N] ceramics with 0.26 ≤ x ≤ 0.31 were sintered at 1100 °C, and their energy harvesters were fabricated. All specimens exhibit a similar energy convergence efficiency. However, the transduction coefficient (d₃₃ × g₃₃) increased with x, reaching 21.5 × 10^?15 m²/N for the x = 0.31specimen; the figure-of-merit of the specimens shows a similar variation. The output energy density of the energy harvester also increased with x, and a high output energy density of 231 mW/cm³ was obtained for the harvester fabricated using the x = 0.31 specimen, indicating that the d₃₃ × g₃₃ value significantly affects the output energy density of the energy harvester.     

Reaction sintering of lead zinc niobate–lead zirconate titanate ceramics

Lead zinc niobate (PZN)–lead zirconate titanate (PZT) ceramics were produced by the reaction-sintering process. The specimens were prepared directly from a mixture of their constituent oxides without any calcination step. When 50% PZN was added to tetragonal Pb(Zr_0.47Ti_0.53)O₃ ceramics, the densities and electrical properties were found to be optimal (ρ = 7.91 g/cm³, K = 1947 at 1 kHz and room temperature, d₃₃ = 530 pC/N, k_p = 0.61). However, the specimen containing more than 50% PZN showed reduced density and decreased electrical properties, due to the formation of pyrochlore phases. The improved densification behavior of the reaction-sintering process was attributed to the enhanced diffusion of lattice defects, which were created by differences in the ionic valence of the B-sites ions of the perovskite structure.     

Identification of Substitution Mechanism in Group VIII Metal Oxides Doped Pb(Zn1/3Nb2/3)O3–PbZrO3–PbTiO3 Ceramics with High Energy Density and Mechanical Performance

Group VIII metal oxides, that is, Fe₂O₃, Co₂O₃, and NiO have been introduced to 0.2Pb(Zn_1/3Nb_2/3)O₃–0.8Pb(Zr_0.50Ti_0.50)O₃ (PZN–PZT) to deterministically identify the substitution mechanism and meantime to tailor mechanical and piezoelectric properties in obtaining energy harvesting materials. On the basis of the X‐ray diffraction and Raman analysis, it is clear that the group VIII metal oxides induce a phase transformation from the morphotropic phase boundary to the tetragonal phase side, and the corresponding grain size increases accordingly. It is reasonable to deduce that two types of substitution behaviors coexist in the group VIII metal oxides added PZN–PZT system. Due to the mixed valence of +2 and +3, the foreign doping ions prefer to enter the B site in the perovskite structure, not only substituting for Ti⁴⁺, Zr⁴⁺, and Nb⁵⁺ ions in the inequivalence replacement but also substituting for Zn²⁺ ions in the equivalence replacement. The proposed complex substitution mechanisms can give the full explanation about the grain growth phenomena and the variation in mechanical and electric properties in the modified PZN–PZT system. At the same doping level of 0.3 mol%, the maximum transduction coefficient (d₃₃·g₃₃ = 13120 × 10^?15 m²/N) and good fracture toughness (K_IC = 1.32 MPa m^1/2) are obtained in Co₂O₃ added 0.2PZN–0.8PZT ceramics, which shows great promise as practical materials for energy harvesting device applications.     

Low-temperature-sintered Bi0.5Na0.5TiO3-based lead-free ferroelectric ceramics with good piezoelectric properties

Li₂CO₃ has been used as a sintering aid for fabricating lead-free ferroelectric ceramic 0.93(Bi_0.5Na_0.5TiO₃)-0.07BaTiO₃. A small amount (0.5 wt%) of it can effectively lower the sintering temperature of the ceramic from 1200 °C to 980 °C. Unlike other low temperature-sintered ferroelectric ceramics, the ceramic retains its good dielectric and piezoelectric properties, giving a high dielectric constant (1570), low dielectric loss (4.8%) and large piezoelectric coefficient (180 pC/N). The “depolarization” temperature is also increased to 100 °C and the thermal stability of piezoelectricity is improved. Our results reveal that oxygen vacancies generated from the diffusion of the sintering aid into the lattices are crucial for realizing the low temperature sintering. Owing to the low sintering temperature and good dielectric and piezoelectric properties, the ceramics, especially of multilayered structure, should have great potential for practical applications.     

Low temperature sintering and high piezoelectric properties of strontium doped PNZT–PNN ceramics processed via the columbite route

This study investigated the influence of strontium doping on both the sintering behavior and the piezoelectric properties of PNZT–PNN ceramics. The piezoelectric ceramics was produced by solid state reaction between metallic oxides, strontium carbonates (SrCO₃) and oxides precursors. NiNb₂O₆ precursors were mixed with the oxides to avoid the large-scale formation of pyrochlore phases during the sintering process and to favor the formation of the perovskite structure. Sintering experiments were accomplished between 900 °C and 1100 °C for PNZT–PNN with 0–4 mol% strontium. Dilatometer curves indicated that the densification of these samples occurs by 850 °C and the electromechanical characterization showed that strontium doping enhances the soft piezoelectric properties of the PZT–PNN ceramics.Consequently, a sintering temperature of 900 °C is sufficient to obtain doped PZT–PNN tablets with 99% of the theoretical density and excellent soft piezoelectric properties (ɛ_r > 4000; K_p > 60; d₃₃ > 1000 pm/V). This makes those ceramics suitable for the construction of high efficiency actuators with low sintering temperature. The low Curie temperature is the only drawback of this material for some applications such as engine fuel injection.     

High-power properties of piezoelectric hard materials sintered at low temperature for multilayer ceramic actuators

0.05Pb(Mn_1/3Sb_2/3)O₃–0.05Pb(Al_1/2Nb_1/2)O₃–0.9Pb(Zr_0.48Ti_0.52)O₃ (PMS–PAN–PZT) high power piezoelectric system with both La₂O₃ as a hardener and CuO as a low sintering agent had been synthesized at 900 °C for 2 h. When La₂O₃ doping of the main composition went over 0.5 wt%, the mixed tetragonal and rhombohedral perovskite structure changed to pure rhombohedral perovskite structure. In case of the CuO, 1.0 and 1.5 wt% CuO content significantly improved the sinterability of the PMS–PAN–PZT system processed at 900 °C for 2 h. When La₂O₃ and CuO co-doped in PMS–PAN–PZT ceramics, piezoelectric constants (d₃₃), quality factor (Q_m), electromechanical coupling factor (k_p) and dielectric constant (${\epsilon }_3^{\text{T}}/{\epsilon }_0$) of the piezoelectric ceramics sintered at 900 °C for 2 h were optimized, such as 336 pC/N, 841, 60%, and 1358, respectively. New developed piezoelectric materials are promising for high power multilayer ceramic actuators.     

Enhanced piezoelectric response and high-temperature sensitivity by site-selected doping of BiFeO3-BaTiO3 ceramics

Effect of Zn site-selected doping on electrical properties, high-temperature stability and sensitivity of piezoelectric response for BiFeO₃-BaTiO₃ ceramics was investigated. The results revealed that the addition of Zn leaded to an evident modification of the microstructure. The B-site selected doping was a more effective approach in improving piezoelectric properties as well as their thermal stability than those of A-site selected doping. Moreover, the enhanced piezoelectric properties accompanying by excellent high-temperature stability and sensitivity in B-site selected doping ceramics were obtained. The microstructure, domain switching behavior and temperature-dependent piezoelectric response in Zn site-selected doping ceramics were investigated, and their relationships with improving piezoelectric properties and high-temperature stability were explored. These results showed that the B-site selected doping ceramics had excellent piezoelectric properties (d₃₃ = 192pC/N) along with a high-temperature stability (T_d = 450 °C).     

Piezoelectric and mechanical properties of CaO reinforced porous PZT ceramics with one-dimensional pore channels

The formation of capillaries in sodium alginate gels is a dissipative process driven by unidirectional diffusion of divalent cations into sodium alginate sols. In the present work, we have prepared 3-1 type porous lead zirconate titanate (PZT) ceramics with oxides (CaO) being doped on a molecular level from the dissipative process by incorporating PZT particles into the sodium alginate gel matrix. By varying the concentration of cation solutions (CaCl₂) from 0.5 mol/L to 2.5 mol/L, both the microstructure, doping amount of oxides (CaO) and crystalline phase of the porous PZT ceramics were tailored. Accordingly, increase in the concentration of Ca²⁺ has led to a reduction in the relative permittivity (ε_r) first, and then an increase, while the piezoelectric coefficient (d₃₃ and d₃₁) demonstrated an opposite variation tendency. The prepared samples possessed a maximal HFOM value of 4755×10^–15 Pa⁻¹ when the concentration of Ca²⁺ was 1.0 mol/L. Addition of CaO was found to improve the compressive strength of porous PZT ceramics, which was preferential to promoting the stability and reliability for application.