采用固相法制备了Bi2O3掺杂的Ba0.85Ca0.15(Zr0.1Ti0.88Mn0.02)O3压电陶瓷，研究了体系的微观结构，以及Bi2O3掺杂量对体系压电性能的影响；将体系最优性能的样品装配成微型气泵，并与日本村田的MZB1001T02微型泵进行了性能对比。研究表明，Bi2O3掺杂Ba0.85Ca0.15(Zr0.1Ti0.88Mn0.02)O3的无铅压电陶瓷呈单一的钙钛矿结构，少量的Bi2O3掺杂使体系保持了三方-四方相共存的特性。当掺杂量(质量分数)为0.05%时，样品晶粒分布均匀，介电和压电性能最优，即εT33=5 289、kp=0.46、d33=377 pC/N、tan δ=0.72%、Tc=80 ℃，样品具有典型的介电弛豫特性。将上述样品装配在微型气泵中，在输入频率(25±2) kHz、输入电压15 V条件下，测得微型气泵的气压略低于日本村田的微型泵。在某些对气压要求不高的领域，样品能够满足使用要求。

Lead-free piezoelectric sodium bismuth titanate ((Bi0.5Na0.5)TiO₃, BNT) thin films were epitaxially grown onto (001)-, (110)-, and (111)-oriented Nb:SrTiO₃ (STO) single crystal substrates prepared by sol–gel processing. Highly oriented growth in (001), (110), and (111) BNT thin films was obtained in this work benefiting from the lattice match between the BNT film and the STO substrate. The different growth models in thin films with various orientations result in various surface morphologies dependent on the film orientation. The piezoresponse of the BNT thin films was represented exhibiting a strong orientation dependence that (110)>(001)>(111). This is contributed by the various domain switching contribution related to the crystal symmetry and polarization distribution in the three oriented thin films.

Considering the advantages of high Curie temperature and environment-friendly nature of KNN piezoelectric ceramics, the limitation of weak piezoelectric response and their temperature sensitivity to applications is worth exploring. Herein, the <001> textured (1-x)(K0.5Na0.5)(Nb0.96Sb0.04)O₃-x(Bi0.5Na0.5)HfO₃(x = 0.01−0.045) lead-free ceramics were synthesized by templated grain-growth method. The high piezoelectric performance (d33 of 474 pC/N and strain of 0.21%) and excellent temperature stability (unipolar strain maintained within 4.3% change between 30∘C and 165∘C) were simultaneously achieved in the textured KNNS-0.03BNH ceramics. The high piezoelectric performance can be attributed to the summation of the crystallographic anisotropy and phase structure contributions in <001> textured ceramics. The superior temperature stability of piezoelectric properties can be interpreted by the contribution of crystal anisotropy to piezoelectric properties reduces the effect of phase transition on piezoelectric properties deterioration. This study provides an effective strategy for simultaneously achieving high piezoelectric properties and superior temperature stability in KNN-based textured ceramics.Considering the advantages of high Curie temperature and environment-friendly nature of KNN piezoelectric ceramics, the limitation of weak piezoelectric response and their temperature sensitivity to applications is worth exploring. Herein, the <001> textured (1-x)(K0.5Na0.5)(Nb0.96Sb0.04)O₃-x(Bi0.5Na0.5)HfO₃(x = 0.01−0.045) lead-free ceramics were synthesized by templated grain-growth method. The high piezoelectric performance (d33 of 474 pC/N and strain of 0.21%) and excellent temperature stability (unipolar strain maintained within 4.3% change between 30∘C and 165∘C) were simultaneously achieved in the textured KNNS-0.03BNH ceramics. The high piezoelectric performance can be attributed to the summation of the crystallographic anisotropy and phase structure contributions in <001> textured ceramics. The superior temperature stability of piezoelectric properties can be interpreted by the contribution of crystal anisotropy to piezoelectric properties reduces the effect of phase transition on piezoelectric properties deterioration. This study provides an effective strategy for simultaneously achieving high piezoelectric properties and superior temperature stability in KNN-based textured ceramics.

Solid solution samples of the three-component system (1 − x)Pb(Ti0.5Zr0.5)O3−xCdNb₂O₆ with x = 0.0125–0.0500, Δx = 0.0125 were obtained by solid phase synthesis followed by sintering using conventional ceramic technology. The crystal structure, microstructure, electrophysical, and thermophysical properties of these ceramics have been studied. It is shown that all studied solid solutions can be divided into two groups (with x = 0.0125 and with x> 0.0125), characterized by different characteristics of the change in properties with variations in external influences. This is probably due to the transition from a perovskite-type structure with a tetragonal (T) unit cell to inhomogeneous solid solutions consisting of a series of T-phases with similar cell parameters. A conclusion is made about the expediency of using the data obtained in the development of similar materials for devices based on them.Solid solution samples of the three-component system (1 − x)Pb(Ti0.5Zr0.5)O3−xCdNb₂O₆ with x = 0.0125–0.0500, Δx = 0.0125 were obtained by solid phase synthesis followed by sintering using conventional ceramic technology. The crystal structure, microstructure, electrophysical, and thermophysical properties of these ceramics have been studied. It is shown that all studied solid solutions can be divided into two groups (with x = 0.0125 and with x> 0.0125), characterized by different characteristics of the change in properties with variations in external influences. This is probably due to the transition from a perovskite-type structure with a tetragonal (T) unit cell to inhomogeneous solid solutions consisting of a series of T-phases with similar cell parameters. A conclusion is made about the expediency of using the data obtained in the development of similar materials for devices based on them.

In this work, Ba1−xCaxTi0.88Zr0.12O₃ (x= 0.00–0.25) ceramics were prepared by a solid-state reaction method, and the variation of dielectric, ferroelectric and piezoelectric characteristics has been investigated together with the structure evolution. The crystal structure varies from rhombohedral to tetragonal at room-temperature and the morphotropic phase boundary (MPB) is determined around x= 0.10, where the significantly enhanced ferroelectric and piezoelectric properties are achieved. With the increase of Ca content, the system gradually evolves into a relaxor ferroelectric. This work provides useful guidance for future research on lead-free piezoelectric materials.In this work, Ba1−xCaxTi0.88Zr0.12O₃ (x= 0.00–0.25) ceramics were prepared by a solid-state reaction method, and the variation of dielectric, ferroelectric and piezoelectric characteristics has been investigated together with the structure evolution. The crystal structure varies from rhombohedral to tetragonal at room-temperature and the morphotropic phase boundary (MPB) is determined around x= 0.10, where the significantly enhanced ferroelectric and piezoelectric properties are achieved. With the increase of Ca content, the system gradually evolves into a relaxor ferroelectric. This work provides useful guidance for future research on lead-free piezoelectric materials.

Pb0.96Sr0.04(Zr,Ti)0.7(Zn1/3Nb2/3)0.3O₃ (PZN–PZT) piezoceramics with various Zr/Ti ratios and Li₂CO₃ sintering aid were sintered at 900^∘C by the solid-state reaction route. The samples with different Zr/Ti ratios were compared according to microstructure, phase structure, piezoelectricity, ferroelectricity, and dielectric relaxation. The Zr/Ti ratio in the PZN–PZT ceramics greatly affects the electrical properties. The Zr/Ti ratio affects the proportion between the rhombohedral and tetragonal phases and also affects the grain size. The PZN–PZT ceramics with the Zr/Ti ratio of 53:47 have the largest grain size and have optimized piezoelectric properties (kp = 0.58, d33 = 540 pC/N, and TC = 250^∘C). The larger the grain size, the lesser the grain boundary, the easier the domain wall motion, and the better the piezoelectric properties. The PZT ceramic with Zr/Ti ratio of 53:47 locates the morphotropic phase boundary (MPB) region which is one of the key factors for the high piezoelectric properties of the PZT.Pb0.96Sr0.04(Zr,Ti)0.7(Zn1/3Nb2/3)0.3O₃ (PZN–PZT) piezoceramics with various Zr/Ti ratios and Li₂CO₃ sintering aid were sintered at 900^∘C by the solid-state reaction route. The samples with different Zr/Ti ratios were compared according to microstructure, phase structure, piezoelectricity, ferroelectricity, and dielectric relaxation. The Zr/Ti ratio in the PZN–PZT ceramics greatly affects the electrical properties. The Zr/Ti ratio affects the proportion between the rhombohedral and tetragonal phases and also affects the grain size. The PZN–PZT ceramics with the Zr/Ti ratio of 53:47 have the largest grain size and have optimized piezoelectric properties (kp = 0.58, d33 = 540 pC/N, and TC = 250^∘C). The larger the grain size, the lesser the grain boundary, the easier the domain wall motion, and the better the piezoelectric properties. The PZT ceramic with Zr/Ti ratio of 53:47 locates the morphotropic phase boundary (MPB) region which is one of the key factors for the high piezoelectric properties of the PZT.

Ceramics of quasi-binary concentration section (x = 0.50, 0.1 ≤y≤ 0.2, Δy = 0.025) of the ternary solid solution system (1−x−y)BiFeO₃–xPbFe0.5Nb0.5O₃–yPbTiO₃ were prepared by the conventional solid-phase reaction method. By using X-ray diffraction technique, the phase diagram of the system was constructed, which was shown to contain the regions of cubic and tetragonal symmetry and the morphotropic phase boundary between them. Grain morphology, dielectric and piezoelectric properties of the selected solid solutions were investigated. The highest piezoelectric coefficient d33= 260 pC/N was obtained. Dielectric characteristics of ceramics revealed ferroelectric relaxor behavior, a region of diffuse phase transition from the paraelectric to ferroelectric phase in the temperature range of 350–500 K.Ceramics of quasi-binary concentration section (x = 0.50, 0.1 ≤y≤ 0.2, Δy = 0.025) of the ternary solid solution system (1−x−y)BiFeO₃–xPbFe0.5Nb0.5O₃–yPbTiO₃ were prepared by the conventional solid-phase reaction method. By using X-ray diffraction technique, the phase diagram of the system was constructed, which was shown to contain the regions of cubic and tetragonal symmetry and the morphotropic phase boundary between them. Grain morphology, dielectric and piezoelectric properties of the selected solid solutions were investigated. The highest piezoelectric coefficient d33= 260 pC/N was obtained. Dielectric characteristics of ceramics revealed ferroelectric relaxor behavior, a region of diffuse phase transition from the paraelectric to ferroelectric phase in the temperature range of 350–500 K.

Dense (Na0.5K0.5)NbO₃ lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure (pO₂, ∼10−12 atm) atmosphere and adding LiF. All the ceramics have pure orthorhombic structure. Compared to the LiF-added (Na0.5K0.5)NbO₃ ceramics sintered in air and the low pO₂-sintered pure (Na0.5K0.5)NbO₃ ceramics without LiF addition, the present ceramics exhibit improved piezoelectric and ferroelectric properties. The piezoelectric constant d33 is 125 pC/N, and the converse piezoelectric constant d33* is 186 pm/V. The dielectric constant and dielectric loss of the ceramics at room temperature and 1 kHz are 451 and 0.03, respectively. Under the measured electric field of 70 kV/cm, the remanent polarization is 25.9 μC/cm² and the coercive field is 13.9 kV/cm. Furthermore, if the base metals such as Cu and Ni powders were mixed into the green pellets and sintered in the low pO₂ atmosphere, the base metals cannot be oxidized, suggesting possibility of using base metals as electrodes.Dense (Na0.5K0.5)NbO₃ lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure (pO₂, ∼10−12 atm) atmosphere and adding LiF. All the ceramics have pure orthorhombic structure. Compared to the LiF-added (Na0.5K0.5)NbO₃ ceramics sintered in air and the low pO₂-sintered pure (Na0.5K0.5)NbO₃ ceramics without LiF addition, the present ceramics exhibit improved piezoelectric and ferroelectric properties. The piezoelectric constant d33 is 125 pC/N, and the converse piezoelectric constant d33* is 186 pm/V. The dielectric constant and dielectric loss of the ceramics at room temperature and 1 kHz are 451 and 0.03, respectively. Under the measured electric field of 70 kV/cm, the remanent polarization is 25.9 μC/cm² and the coercive field is 13.9 kV/cm. Furthermore, if the base metals such as Cu and Ni powders were mixed into the green pellets and sintered in the low pO₂ atmosphere, the base metals cannot be oxidized, suggesting possibility of using base metals as electrodes.

Effective piezoelectric properties, electromechanical coupling factors (ECF) and figures of merit (FOM) are studied in lead-free 0–3-type composites based on novel ferroelectric 0.965(K0.48Na0.52)(Nb0.96Sb0.04)O₃–0.035Bi0.5Na0.5Zr0.15Hf0.75O₃ ceramic. Systems of prolate ceramic inclusions are surrounded by a large polymer matrix that can be either monolithic (in the 0–3 composite) or porous (in the 0–3–0 composite). Non-monotonic volume-fraction dependences of the effective piezoelectric coefficients g3j∗, ECF k3j∗, squared FOM d3j∗g3j∗ and their modified analogs for stress-driven systems are analysed, and examples of the high longitudinal piezoelectric sensitivity (g33∗> 100 mV ⋅m/N) are considered. A role of microgeometrical factors, that promote the large effective parameters and anisotropy of properties in the 0–3-type composites, is highlighted. New “aspect ratio — volume fraction” diagrams are first built to describe conditions for high piezoelectric sensitivity, large modified FOM and their anisotropy in the studied composites. These advanced materials can be of value for piezoelectric sensor, energy-harvesting and related applications.Effective piezoelectric properties, electromechanical coupling factors (ECF) and figures of merit (FOM) are studied in lead-free 0–3-type composites based on novel ferroelectric 0.965(K0.48Na0.52)(Nb0.96Sb0.04)O₃–0.035Bi0.5Na0.5Zr0.15Hf0.75O₃ ceramic. Systems of prolate ceramic inclusions are surrounded by a large polymer matrix that can be either monolithic (in the 0–3 composite) or porous (in the 0–3–0 composite). Non-monotonic volume-fraction dependences of the effective piezoelectric coefficients g3j∗, ECF k3j∗, squared FOM d3j∗g3j∗ and their modified analogs for stress-driven systems are analysed, and examples of the high longitudinal piezoelectric sensitivity (g33∗> 100 mV ⋅m/N) are considered. A role of microgeometrical factors, that promote the large effective parameters and anisotropy of properties in the 0–3-type composites, is highlighted. New “aspect ratio — volume fraction” diagrams are first built to describe conditions for high piezoelectric sensitivity, large modified FOM and their anisotropy in the studied composites. These advanced materials can be of value for piezoelectric sensor, energy-harvesting and related applications.

Doping effects of CuO on the sintering behavior and electrical properties of 0.94(Bi0.5Na0.5)TiO₃–0.06(BaTiO3)–xCuO (BNT–BT6–xCu) lead-free piezoceramic obtained by the conventional solid-state reaction method were investigated. Regarding the undoped system, it is already known that it presents the best densification values when it is sintered at 1150∘C, however, the doped system was sintered at 1150∘C, 1100∘C, 1050∘C, 1025∘C, and 975∘C to determine the effect of Cu on the densification process. Therefore, it was obtained that the CuO-doped samples sintered at 1050∘C presented the highest density values and therefore were the ones chosen to perform the characterization tests together with the undoped system. The samples were characterized using X-ray diffraction (XRD), Raman microspectroscopy, and scanning electron microscopy (SEM) analysis, whereas the ferroelectric and dielectric properties were evaluated by means of ferroelectric hysteresis loops and impedance spectroscopy studies. As a result, the addition of CuO allowed an improvement in sinterability and densification, with the subsequent grain growth, and the improvement of the piezoelectric coefficient (d33).Doping effects of CuO on the sintering behavior and electrical properties of 0.94(Bi0.5Na0.5)TiO₃–0.06(BaTiO3)–xCuO (BNT–BT6–xCu) lead-free piezoceramic obtained by the conventional solid-state reaction method were investigated. Regarding the undoped system, it is already known that it presents the best densification values when it is sintered at 1150∘C, however, the doped system was sintered at 1150∘C, 1100∘C, 1050∘C, 1025∘C, and 975∘C to determine the effect of Cu on the densification process. Therefore, it was obtained that the CuO-doped samples sintered at 1050∘C presented the highest density values and therefore were the ones chosen to perform the characterization tests together with the undoped system. The samples were characterized using X-ray diffraction (XRD), Raman microspectroscopy, and scanning electron microscopy (SEM) analysis, whereas the ferroelectric and dielectric properties were evaluated by means of ferroelectric hysteresis loops and impedance spectroscopy studies. As a result, the addition of CuO allowed an improvement in sinterability and densification, with the subsequent grain growth, and the improvement of the piezoelectric coefficient (d33).