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Piezoelectric ceramics with high electrical performances and high Curie temperature (Tc) act as key materials for numerous electromechanical devices such as transducers and actuators. Herein, we report a systematic investigation on the crystal structure, microstructure and electrical properties of Sr and La co-doped Pb(Mg1/3Nb2/3)O3–PbZrO3–PbTiO3 ceramics with a low Pb(Mg1/3Nb2/3)O3 content, namely, (Pb1−ySry)(Mg1/3Nb2/3)0.07ZrxTi0.93−xO3:zLa. With an increase in the Zr content (x value) from 0.49 to 0.53, its crystal structure evolved from a tetragonal phase to a rhombohedral phase, leading to not only a morphotropic phase boundary (MPB) at around x = 0.51 but also a monotonously decreasing Tc. Meanwhile, a change in either the Sr- or La-doping content (y and z values, respectively) in the range of y = 0.03–0.07 and z = 0.01–0.03 can slightly deviate the structure of MPB, resulting in a significant effect on its electrical properties. As the best results, the optimal composition of x = 0.51, y = 0.05, and z = 0.02 yielded peak electrical performance, with a related room temperature piezoelectric coefficient (d33) of 645 pC N−1, remanent polarization (Pr) of 33.5 μC cm−2, coercive field (Ec) of 8.6 kV cm−1, and Tc of 242 °C. Especially, its piezoelectric properties showed excellent temperature stability, and its d33 value decreased by only 3% from room temperature to 150 °C. This work not only provides an alternative piezoelectric ceramic with outstanding electrical performance for industrial applications, but also reveals a comprehensive perspective on the composition–structure–property relationship of doped Pb[(Mg1/3Nb2/3),Zr,Ti]O3, which is helpful for further work on piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Lead-free Ba0.70Ca0.30TiO3 + x mol% MnO2 (abbreviated as BCTMx, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0 and 1.2) piezoelectric ceramics were synthesized by the solid-state reaction method. The effects of MnO2 additives on the phase transition, microstructure, dielectric, ferroelectric, strain behaviors and piezoelectric properties are investigated. BCTMx ceramics (x = 0–1.2) exhibit diphasic tetragonal and orthorhombic phases. The tetragonal phase is gradually suppressed by increasing x. As x increases from 0 to 1.2, the Curie temperature (TC) decreases monotonically from 128 to 45 °C, while the grain size, dielectric and ferroelectric properties increase and reach the maximum near x = 0.6. On the other hand, the piezoelectric coefficient (d33) and the electromechanical coupling coefficient (kp%) decrease simultaneously, whereas the mechanical quality factor (Qm), bipolar and unipolar strain increase and reach the maximum values of 684, 0.28% and 0.24%, respectively, near x = 0.6. The optimum electrical performance with ε r = 1323, tan δ = 0.08, TC = 66 °C, Pmax = 12.2 μC/cm2, Pr = 6.9 μC/cm2, EC = 13.3 kV/cm, d33 = 116 pC/N, kp% = 0.22%, Qm = 684 and the normalized strain d 33 ∗ = Smax/Emax as high as 480 pm/V were observed for x = 0.6. The high strain and Qm suggested that the MnO2-modified Ba0.70Ca0.30TiO3 ceramics are promising candidate for high power applications. [ABSTRACT FROM AUTHOR]

Lead-free (1-x)Bi0.5Na0.5TiO3-xBiCoO3 (x = 0, 0.015, 0.025, 0.03, 0.035, 0.04, and 0.06) piezoelectric ceramics have been synthesized and their structure and electric properties have been investigated systemically. The rhombohedral-tetragonal morphotropic phase boundary (MPB) locates near x = 0.025-0.035. For the ceramics with x = 0.025, the saturated polarization (Ps), remnant polarization (Pr), coercive field (Ec), strain(S), piezoelectric constant (d33), and thickness electromechanical coupling factor (kt) are 40.6 μC/cm2, 35.4 μC/cm2, 5.25 kV/mm, 0.11%, 107pC/N, and 0.45, respectively. The low temperature humps of relative dielectric constant, which is indicative of TR-T, are becoming inconspicuous gradually with the increasing x and almost disappear at x = 0.04. The depolarization temperature Td decreases first and then increases with the increasing x. Our results may be helpful for further work on Bi0.5Na0.5TiO3-based lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Ferro‐/piezoelectric ceramics with high performances are generally found at the morphotropic phase boundary (MPB), where two or more different ferroelectric phases coexist. However, the MPB region is usually very narrow; for example, that of (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN‐xPT) locates between x = 0.30−0.34. Herein, we report that ZnO‐modified PMN‐xPT polycrystalline ceramics have dramatically broadened MPB regions from x = 0.28, with rhombohedral and monoclinic coexisting phases, to x = 0.36, with tetragonal and monoclinic coexisting phases, as confirmed by powder X‐ray diffraction and piezoresponse force microcopy measurements. The wide MPB region is attributed to lattice distortion caused by the substitution of Zn for Mg cations. As a result, the ceramics show composition insensitive electrical properties over wide composition ranges; for example, the piezoelectric coefficient (d33) and electromechanical coupling factor (kp) remain at near constant values of 450 pC/N and 0.5, respectively, in the range from x = 0.28−0.34. This work not only provides a robust and feasible method to broaden the MPB region but also offers some novel insights into promoting fundamental research on high‐performance piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Er-doped 0.94 Bi0.5 Na0.5 TiO3-0.06 BaTiO3 ( BNT-6 BT: x Er, x is the molar ratio of Er3+ doping) lead-free piezoceramics with x = 0-0.02 were prepared and their multifunctional properties have been comprehensively investigated. Our results show that Er-doping has significant effects on morphology of grain, photoluminescence, dielectric, and ferroelectric properties of the ceramics. At room temperature, the green (550 nm) and red (670 nm) emissions are enhanced by Er-doping, reaching the strongest emission intensity when x = 0.0075. The complex and composition-dependent effects of electric poling on photoluminescence also have been measured. As for electrical properties, on the one hand, Er-doping tends to flatten the dielectric constant-temperature (εr- T) curves, leading to temperature-insensitive dielectric constant in a wide temperature range (50°C-300°C). On the other hand, Er-doping significantly decreases the ferroelectric-relaxor transition temperature ( TF-R) and depolarization temperature ( Td), with the TF-R decreasing from 76°C to 42°C for x = 0-0.02. As a result, significant composition-dependent electrical features were found in ferroelectric and piezoelectric properties at room temperature. In general, piezoelectric and ferroelectric properties tend to become weaker, as confirmed by the composition-dependent piezoelectric coefficient ( d33), planar coupling factor ( kp), and the shape of polarization-electric field ( P- E), current-electric field ( J-E), bipolar/unipolar strain-electric field ( S-E) curves. Furthermore, to understand the relationship between the TF-R/ Td and the electrical properties, the composition of x = 0.0075 has been intensively studied. Our results indicate that the BNT-6 BT: x Er with appropriate Er-doping may be a promising multifunctional material with integrated photoluminescence and electrical properties for practical applications. [ABSTRACT FROM AUTHOR]

Lead-free piezoceramics of (1 − x)BiNaTiO- xBaSnO (BNT-BS, x = 0, 0.02, 0.03, 0.04, 0.06, 0.09 and 0.12) have been synthesized and investigated. A rhombohedral-tetragonal morphotropic phase boundary (MPB) exists near x = 0.03. The MPB composition shows improved electrical properties: the saturated polarization, remnant polarization, coercive field, piezoelectric coefficient, planar electromechanical coupling factor, and unipolar strain are 35.8, 28.5 μC/cm, and 4.5 kV/mm, 93 pC/N, 0.19, and 0.18 %, respectively. It is also found the introduction of BS can significantly enhance dielectric property. The structural and electrical properties are discussed by comparing with other BNT-based piezoceramics. [ABSTRACT FROM AUTHOR]

A series of layered n-ABO3-doped Aurivillius structures Bi4Ti3012 (BTO) thin films are synthesized on (001) SrTiO3 (STO) substrates by pulsed laser deposition, where n represents the number of ABO3 perovskite. X-ray diffraction substantiates that these films have expected layered Aurivillius structures. Furthermore, the microstructure of these samples is "systematically" characterized by transmission electron microscopy. It is found that the structure of n-STO-doped BTO becomes unstable when n is equal to 3, as revealed by the occurrence of intergrowth. Similar phenomenon is observed in n-LaFeO3-doped BTO; the layered Aurivillius structure is totally collapsed in the case of n as high as 2.5. In contrast, 3-BiFeO3-doped BTO still keeps perfect Aurivillius structure. The above-observed structural stabilities of these materials are explained by the theoretical formation enthalpy calculated by the density functional theory. This work provides the necessary information to explore the multifunctionality based on Aurivillius n-ABO3-BTO oxides. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of (1 − x) Ba0.70 Ca0.30 TiO3- x BiFeO3 [(1 − x) BCT- x BF, x = 0-0.065] have been prepared and investigated. The ceramics with x ≤ 0.06 have diphasic tetragonal and orthorhombic crystal structures, whereas tetragonal phase is suppressed by the introduction of BF. As a result, the composition with x = 0.065 is found to have diphasic pseudocubic and orthorhombic phases. Significantly composition-dependent grain size is observed. With increasing x from 0 to 0.065, the ferroelectric-paraelectric phase transition temperature decreases monotonically from 128°C to 50°C, accompanied by enhanced ferroelectric relaxor behavior, as indicated by the widened diffused phase transition temperature. The room temperature polarization-electric field ( P-E) hysteresis loops and strain-electric field ( S-E) curves indicate that the ferroelectricity enhances slightly and reaches the maximum near x = 0.05, and then weakens with increasing x. On the other hand, the piezoelectric coefficient ( d 33) and electromechanical coupling coefficient ( kp) decrease simultaneously with increasing x, whereas the mechanical quality factor ( Qm) reaches the maximum near x = 0.05. The structure-property relationship is discussed intensively. Our results may be helpful for further understanding and designing BaTiO3-related lead-free ferroelectric/piezoelectric materials. [ABSTRACT FROM AUTHOR]

Abstract: Bi0.5Na0.5TiO3–BaTiO3–Bi0.5K0.5TiO3 (BNT–BT–BKT) lead-free piezoceramics with compositions near the rhombohedral–tetragonal morphotropic phase boundary (MPB) were prepared and investigated. At room temperature, all ceramics show excellent electrical properties. In this study, the best properties were observed in 0.884BNT–0.036BT–0.08BKT, with the remnant polarization, bipolar total strain, unipolar strain, piezoelectric constant, and planar electromechanical coupling factor being 34.4μCcm−2, 0.25%, 0.15%, 122pCN−1, and 0.30, respectively. Detailed analysis of the temperature dependence of polarization–electric field (P–E) loops and bipolar/unipolar strain–electric field (S–E) curves of this composition revealed a ferroelectric–antiferroelectric phase transition around 100°C. Around this temperature, there is a significant shape change in both P–E and S–E curves, accompanied by enhanced strain and decreased polarization; the largest recoverable strain reaches 0.42%. These results can be explained by the formation of antiferroelectric order and the contribution of field-induced antiferroelectric–ferroelectric phase transition to piezoelectric response. Our results indicate that BNT–BT–BKT lead-free piezoceramics can have excellent electrical properties in compositions near the MPB and also reveal some insight into the temperature dependence of the electrical performance with the MPB composition. [Copyright &y& Elsevier]

The enhanced and reliable high-power performance of x Pb(Mn 1/3 Nb 2/3)O 3 –(1- x)Pb(Zr 0.5 Ti 0.5)O 3 –0.5mol%Co 2 O 3 piezoelectric ceramics (x PMN–(1- x)PZT–Co; x = 0.04–0.10) has been achieved. It is noteworthy that the vibration velocity (υ 0) of the 0.08PMN–0.92PZT–Co ceramic reaches up to 0.9 m/s, which is 2.25 times that of commercial PZT4 ceramics (∼0.4 m/s). The high υ 0 of the 0.08PMN–0.92PZT–Co ceramic is attributed to its excellent electromechanical parameters: d 33 = 405 pC/N, Q m = 1405, and k p = 0.61. The 0.08PMN–0.92PZT–Co ceramic achieves a relatively low high-field tan δ (tan δ = 3.74% at 500 V/mm), thereby suppressing heat generation. Additionally, the significantly high Curie temperature (T c) value of 346 °C for the 0.08PMN–0.92PZT–Co ceramic stabilizes the ferroelectric phase. Therefore, the 0.08PMN–0.92PZT–Co ceramic exhibits long-term reliable high-power performance by maintaining a stable υ 0 of 0.9 m/s and slight temperature rise within 100 min. [ABSTRACT FROM AUTHOR]

Grain-oriented Pb(Mg 1/3 Nb 2/3)O 3 -PbZrO 3 -PbTiO 3 (PMN-PZ-PT) based ceramics were synthesized through templated grain growth via using BaTiO 3 (BT) templates. Although BT templates are partially destroyed by PMN-PZ-PT matrix, CuO addition remarkably promotes [001] c -oriented grain growth behavior of the ceramics, resulting in an improvement of Lotgering factor F 001 from ~86% to 98%. Both crystallographic texture and CuO doping increase tetragonality and reduce average domain size of the ceramics dominated by rhombohedral phase. Consequently, 0.50 wt% CuO-doped ceramics (F 001 ~98%) exhibit optimum electromechanical properties: d 33 ~860 pC/N, d 33 × g 33 ~48.6 × 10−12 m2/N, k p ~0.80, E c ~7.2 kV/cm, tan δ ~0.8% and T c ~222 °C. In addition to ~3.7 times and 6.6 times higher d 33 and d 33 × g 33 , those ceramics possess about 240% enhanced piezoelectric strain and much better thermal stability (S max / E max variation ≤2% between RT and 150 °C) relative to non-textured counterpart. This work offers a good paradigm for simultaneously exploring high piezoelectric response and good temperature stability in piezoceramics, benefiting the development of next-generation advanced electromechanical devices. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of Ba0.70Ca0.30Ti1−x Fe x O3 (x=0–0.03) have been synthesized by a conventional solid state reaction method. The influence of Fe content on the microstructure, phase transition, dielectric, ferroelectric, and piezoelectric properties is investigated systematically. The ceramics with x≤0.02 are diphasic composites of tetragonal Ba0.80Ca0.20TiO3:Fe and orthorhombic Ba0.07Ca0.93TiO3:Fe solid solutions. The tetragonal phase is gradually suppressed as x increases, the ceramic with x=0.03 is found to have diphasic pseudocubic and orthorhombic phases. And the grain size is dependent on Fe content significantly. Introduction of Fe at B-sites improves the densification and decreases the sintering temperature. As x increases from 0 to 0.03, the room temperature relative dielectric permittivity enhances, dielectric loss decreases, and the Curie temperature decreases monotonically from 128°C to 58°C. However, the ferroelectricity enhances slightly and reaches the maximum near x=0.005, and then weakens with increasing x. On the other hand, the piezoelectric coefficient (d 33) and the electromechanical coupling coefficient (k p ) decrease simultaneously with increasing x, whereas the mechanical quality factor (Q m ) increases significantly. The structure–electrical properties relationship is discussed intensively to give more information on (Ba,Ca)TiO3-based lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Ba 0.70 Ca 0.30 Ti 1- x (Nb 0.5 Fe 0.5) x O 3 lead-free ceramics (abbreviated as BCTNF x , x = 0–0.12) were prepared by solid-state reaction method. The influence of B-site (Fe 0.5 Nb 0.5)4+ substitution on phase structure, microstructure, dielectric, ferroelectric and piezoelectric properties of Ba 0.70 Ca 0.30 TiO 3 ceramics were systematically studied. The BCTNF x ceramics consist of diphasic tetragonal (T) and orthorhombic (O) phases at x = 0–0.04, pseudocubic (PC) and O phases at x = 0.05–0.08, cubic (C) and O phases at 0.08 < x ≤ 0.12. Increase of (Fe 0.5 Nb 0.5)4+ doping improves sinterability, depresses the ferroelectric - paraelectric phase transition temperature (T m) monotonically from 128 °C at x = 0 to -86 °C at x = 0.12, induces enhanced relaxor behavior and weakens piezoelectric properties. The room temperature relative dielectric constant (ε r) and dielectric loss tangent (tan δ) increase with increasing x and reach the maximum values of 4869 and 0.06 respectively at x = 0.06. Whereas the average grain size (abbreviated as AGS), ferroelectric properties and electric field induced strain increase significantly by introducing 2.0 mol% B-site complex cations (Fe 0.5 Nb 0.5)4+ into Ba 0.70 Ca 0.30 TiO 3 ceramics. The BCTNF0.02 ceramics achieve optimal electrical properties with ε r = 1268, tan δ = 0.03, T m = 102 °C, P max = 12.8 μC/cm2, P r = 6.1 μC/cm2, E C = 6.0 kV/cm, d 33 = 117 pC/N, k p % = 0.18%, Q m = 236, bipolar S max % = 0.20%, unipolar S max % = 0.16% and d 33 ∗ = 314 pm/V. The variation of electrical properties of BCTNF x ceramics is attributed to the combined action of grain size effect, phase transition, weakness of octahedral distortion, clamping effects of the internal bias electric field E i on domain wall motion induced by B-site cations (Fe 0.5 Nb 0.5)4+ displacement. [ABSTRACT FROM AUTHOR]

(1- x)[0.8Na 0.5 Bi 0.5 TiO 3 -0.2K 0.5 Bi 0.5 TiO 3 ]- x BiMn 2/3 Nb 1/3 O 3 ((1- x)NKBT- x BMN with x = 0–0.04) piezoceramics were prepared, the composition-dependent domain structure and domain switching under electric field and their effects on macroscopic electrical properties have been systematically investigated. At room temperature, though the ceramics persists rhombohedral-tetragonal mixed crystal structure, their domain structure evolves from dispersive island-like with average size of 80 nm for x = 0 to labyrinthian-like with average size of 120 nm for x = 0.0075, and then tends to be unobservable by forming polar nanoregions for x = 0.04. As the results, the x = 0.0075 ceramic shows enhanced ferroelectric and piezoelectric property. When compared with the x = 0 pristine counterpart, the saturated polarization, remnant polarization, piezoelectric coefficient, and electromechanical coupling factor of x = 0.0075 ceramic increase by 3%, 12%, 40%, and 20% to 43.2 μC/cm2, 31.2 μC/cm2, 147 pC/N, and 0.28. This work suggests that fine domain engineering is a promising way to further improve electrical property. [ABSTRACT FROM AUTHOR]

Unquenched and quenched ceramics of 0.85Na 0.5 Bi 0.5 TiO 3 -0.11K 0.5 Bi 0.5 TiO 3 -0.04BaTiO 3 have been prepared, and their crystal structure, temperature-dependent ferro-/piezoelectric properties and domain structure have been comparatively investigated. It is shown that quenching process can significantly improve the ferroelectric-relaxor transition temperature (T F-R), which is 130 °C for unquenched ceramics and 198 °C for quenched one. As the result, the thermal stability of ferro-/piezoelectric properties is highly enhanced. These observations are mainly attributed to the quenching induced stable rhombohedral ferroelectric phase and the defect altered domain evolution. This work may deepen the understanding of the effect of quenching on crystal structure, domain structure and their contributions to thermal stability of NBT-based ceramics. [ABSTRACT FROM AUTHOR]

0.8Na 0.5 Bi 0.5 TiO 3 -(0.2- x)K 0.5 Bi 0.5 TiO 3 - x Bi(Zn 0.5 Ti 0.5)O 3 (NBT-KBT-BZT, x = 0–0.05 with interval of 0.01) lead-free piezoceramics were prepared and investigated. The addition of BZT has not led to deviation of rhombohedral-tetragonal morphotropic phase boundary, but apparently composition-dependent electrical property and monotonously improved thermal stability. The x = 0.02 has the optimal electrical property with remnant polarization, bipolar total strain, piezoelectric constant of 26.5 μC/cm2, 0.30%, 121 pC/N respectively, while the depolarization temperature is increased from 93 °C for x = 0–135 °C for x = 0.05 based on dielectric measurement. Detailed investigation reveals that the domain structure transforms from labyrinthian domain for x = 0 to coexistence of nanodomain and labyrinthian domain for x = 0.02, end up with large amount of nanodomain (x = 0.04). Such domain evolution should be responsible for the composition dependent electrical property and improved thermal stability. Our work confirms that domain engineering is an alternative method to develop high performance piezoelectric materials. • NBT-KBT-BZT lead-free piezoceramics have been prepared. • The piezoceramics show composition-dependent property and improved thermal stability. • Domain transforms from labyrinthian domain, coexisted nanodomain and labyrinthian domain, to nanodomain. [ABSTRACT FROM AUTHOR]