TiO3 Lead-free Piezoelectric Ceramics Research Articles

Tuning phase structure for enhanced electrostrain in Nb5+-doped Bi0.5(Na0.81K0.19)0.5TiO3 lead-free piezoelectric ceramics

The synthesis of Bi0.5(Na0.81K0.19)0.5Ti1−xNbxO3 (BNKT-xNb) lead-free piezoelectric ceramics via the traditional solid-state method, with varying x from 0.5 % to 4.0 %, is reported. Investigating the influence of Nb5+ ions on dielectric, ferroelectric, and electrostrain properties, alongside assessing the temperature stability of electrical properties, unveiled a notable electrostrain of 0.46 % at room temperature under 80 kV/cm for the 2.0 mol.% Nb5+ doped composition. The incorporation of Nb5+ prompted a transition from the ferroelectric to the relaxor phase, facilitating reversible induction into the ferroelectric phase under an external electric field, leading to the observed large electrostrain. Leveraging the first-order reversal curve (FORC) approach, a detailed analysis of the dynamic response process of different phase structures under the influence of the external electric field was conducted. This analysis elucidated that the continuous polarization response near the boundary of ferroelectric and relaxor phases, induced by the external electric field, primarily drives strain enhancement. These findings underscore the effective modulation of phase structure through Nb5+ doping, offering significant advancements in strain properties. This study opens avenues for the utilization of the material in micro actuators and provides valuable insights for the development of high-performance lead-free piezoelectric ceramics.

Correlation between Phase Evolution, Physical and Electrical Properties of (Bi0.5(Na0.80K0.20)0.5)1- x (Ba0.7Sr0.3) x TiO3 Lead-Free Piezoelectric Ceramics

The (Bi0.5(Na0.80K0.20)0.5)1- x (Ba0.7Sr0.3) x TiO3 or (BiNK)1- x (BaS) x T (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mol fraction) lead-free piezoelectric ceramics were firstly made by a conventional one step mixed-oxide method and sintered at 1125 °C for 2 h with a heating rate of 5 °C/min. All samples showed optimum relative densities of ∼97–98%. The XRD result indicated that no impurity phase was detected in all fabricated samples. SEM images indicated that all ceramics possessed irregular shaped grains. It was also found that BST added content had an effect on electrical properties of BNKT ceramics. The highest piezoelectric coefficient (d33 = 164 pC/N) with good dielectric (εr = 1577, tanδ = 0.0855) and ferroelectric properties (Pr = 11.38 µC/cm2, Ec = 19.89 kV/cm) were obtained for (BiNK)0.98(BaS)0.02T sample.

Effect of Contents on the Electrical and Piezoelectric Properties of (1 - x)(Bi, Na)TiO3-x(Ba, Sr)TiO3 Lead-Free Piezoelectric Ceramics.

In this study, the composition of lead-free piezoelectric ceramics (1 - x)(Bi0.5Na0.5)TiO3-x(Ba0.5Sr0.5)TiO3 with excellent piezoelectric properties was investigated. Crystal analysis and electrical and piezoelectric properties were analyzed according to the content of the BST composition. A phase change from rhombohedral to tetragonal structure was observed in 0.12 BST, and the densest and most uniform microstructure was confirmed in this composition. The dielectric constant increased from 905 to 1692 as the composition of BST increased to 0.12 BST. Afterward, as the composition of BST increased, the permittivity tended to decrease. Additionally, at 0.12 BST, Pr was the highest at 23.34 μC/cm2. The piezoelectric charge constant (d33) and the electromechanical coupling coefficient (kp) were 152 pC/N and 0.37, respectively, and showed the highest values at 0.12 BST. Curie temperature (Tm) was analyzed 242 °C at 0.12 BST, the optimal composition. It was confirmed that the characteristics of 0.12 BST were excellent in all conditions. Therefore, it was confirmed that 0.12 BST is the optimal composition for (1 - x)BNT-xBST piezoelectric ceramics.

Effect of Different Ca2+ and Zr4+ Contents on Microstructure and Electrical Properties of (Ba,Ca)(Zr,Ti)O3 Lead-Free Piezoelectric Ceramics

In the preparation of (Ba,Ca)(Zr,Ti)O3 lead-free piezoelectric ceramics, different Ca2+ and Zr4+ contents will greatly affect the phase structure, microstructure, and electrical properties of the ceramics. XRD shows that all samples have pure perovskite phase structure, and the (Ba0.85Ca0.15)(ZryTi1−y)O3 ceramics morphotropic phase boundary region from tetragonal phase to rhombohedral phase near 0.08 ≤ y ≤ 0.1. From the dielectric temperature curve, the phase transition temperature (TO-T) was found near room temperature at 0.12 ≤ x ≤ 0.18 for the (Ba1−xCax)(Zr0.1Ti0.9)O3 ceramics. Both Ca2+ and Zr4+ increase have a significant decrease on the Curie temperature Tc. All samples were revealed as relaxers with diffusivities in the range 1.29 ≤ γ ≤ 1.82. Different from the undoped ceramics, ceramics doped with Ca and Zr ions exhibit saturated P–E hysteresis loops, and their ferroelectric properties are significantly optimized. In particular, the (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramic demonstrated optimal properties, namely d33 = 330 pC/N, kp = 0.41, εr = 4069, Pr = 4.8 μC/cm2, and Ec = 3.1 kV/cm, indicating that it is a viable lead-free piezoelectric contender. Variations in Ca and Zr content have a significant effect on the crystal grain sizes and densities of ceramics, which is strongly associated with their piezoelectricity.

Hardening of (Ba0.5Na0.5)0.85Ba0.15TiO3 lead-free piezoelectric ceramics by adding (Bi0.5Na0.5)MnO3

The hardening of (Bi0.5Na0.5)0.85Ba0.15TiO3 (BNBT15) piezoelectric ceramics was investigated by adding raw materials with Bi0.5Na0.5MnO3 (BNM). BNBT15-BNM exhibited a single phase of BNBT15. BNM acts as a sintering aid for BNBT15 to produce domain pinning, and produces tetragonality based on BaTiO3 for increased stability. BNBT15-BNM hardens piezoelectric material with low Mn content, increasing the coercive field and mechanical quality factor. The mechanical quality factor of BNBT15-BNM (0.75 wt%) exceeded 1200. In high-power conditions, BNBT15-BNM (0.75 wt%) exhibited a vibration velocity twice that of hard-PZT. The quality factor gradually decreased with a high vibration velocity. The equivalent stiffness slightly decreased with strain, and the mechanical nonlinearity was much less than that of hard-PZT. BNBT15-BNM (0.75 wt%) has superior high-power properties, and is expected to be a candidate material for use in lead-free piezoelectric ceramics in high-power applications.

Multifunctional bismuth sodium titanate-based ferroelectric ceramics with bright red emission and large strain response

In this paper, we systematically studied the structure and properties of SrPrAlO4-modified (Bi0.5Na0.5)0.935Ba0.065TiO3 (BNT-0.065BT) lead-free piezoelectric ceramics. There is no impurity in the SrPrAlO4-modified BNT-0.065BT, and all samples form pure perovskite structure. The substitution of SrPrAlO4 induces the transformation of ferroelectric to ergodic relaxor phase. As a result, a large electric-field induced strain of 0.35% (@70 kV/cm, corresponds to a large signal piezoelectric d33* (Smax/Emax) of 500 pm/V) is obtained when the SrPrAlO4 dopant concentration is 0.012. In addition, the large strain in this material is very resistant to field cycling, rendering the material attractive for its fatigue-free behavior. Moreover, SrPrAlO4-modified ceramics exhibit orange-red emission under 450 nm photoexcitation. There is a strong red emission peak at 610 nm corresponded to the transition of 1D2 →3H4 and a weak red emission peak at 660 nm ascribed to the 3P0 →3F2 transition. The multifunctional characteristics with good electrical and luminescent properties in BNT-0.065BT-xSrPrAlO4 ceramics render the materials may have broad application prospects in new devices with multiple functions.

Effect of Bi(Zn0.5Ti0.5)O3 substitution on structural and electromechanical properties of Bi0.5(Na0.78K0.22)0.5TiO3 lead-free piezoelectric ceramics

Innovative lead free piezoelectric ceramics ( ) were synthesized by the broadly used solid state reaction method. The outcome of BZT count into the BNKT ceramics was examined by X-ray diffraction (XRD), temperature, field dependent structure, microstructure, dielectric and ferroelectric characterization, and electric field-induced strain. The XRD data revealed that all the synthesized samples have perovskite phase, also a phase transition from tetragonal to pseudocubic phase is observed at The temperature dependent dielectric study showed that as the BZT content increased, the transition point decreased and eventually disappeared at higher concentration of BZT The field emission scanning electron microscope (FESEM) images confirmed an increase in the average grain size of BNKT with increasing BZT content. The polarization and strain hysteresis loops showed that the ferroelectric order of the BNKT ceramics were remarkably disturbed by the addition of BZT, which results in degradation of the remnant polarization and coercive field. Though, the disruption of the ferroelectric order is escorted by a substantial improvement in the unipolar strain which peaks at with a worth of ∼ which resembles to a normalized strain, of 654 pm V−1. The results showed that the composition maintain high value of normalized strain at temperature around (110 °C), suggested that the material is a good candidate for actuator applications working in this temperature range.

Effects of Excess Barium on the Structure and Electrical Properties of (Ba,Ca)TiO3 Piezoelectric Ceramics with High Mechanical Quality Factors

Manganese-doped Ba0.925Ca0.075TiO3 lead-free piezoelectric ceramics (abbreviated as BCT) with high mechanical quality factor were synthesized by conventional solid-state reaction method. The effects of excess Ba on the crystal structure, microstructure, and electrical properties of the ceramics were systematically investigated. X-ray diffraction and Raman spectra revealed that Ca2+ ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol% extra Ba2+ ions were added after sintering. The grain size of the ceramics was decreased by adding extra Ba2+ ions. The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%. High piezoelectric coefficients ( d33 = 150–190 pC/N ) and high mechanical quality factors ( Qm = 1 000–1 200 ) were obtained in the ceramics when the excess of Ba was between 0.5 mol% and 1 mol%. These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.

Piezoelectric properties of (1-x)BZT-xBCT system for energy harvesting applications

In this study, we investigated (1-x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 lead-free piezoelectric ceramics for energy harvester applications. The (1-x)BZT-xBCT ceramic is a promising lead-free piezoelectric material in the field of piezoelectric energy harvesting. Piezoelectric and energy properties of (1-x)BZT-xBCT ceramics were analyzed to confirm the possibility of using them as energy-harvesting materials. Especially, the vicinity of the phase convergence region was investigated to improve their piezoelectric properties. In the phase convergence region, cubic, rhombohedral, orthorhombic, and tetragonal regions co-exist within the narrow region. Near the phase transition region between the orthorhombic and tetragonal phase, the highest piezoelectric property d33 = 464 pC/N and the highest energy density of 158.5 μJ/cm3 were observed. This output energy density of 158.5 μJ/cm3 is the recorded highest value among lead-free ceramics. We found that the optimal sintering temperature was 1475 °C and the optimal composition was BZT-0.5BCT.

Structure and electrical properties of Ca2+-doped (Na0.47Bi0.47Ba0.06)TiO3 lead-free piezoelectric ceramics

The lead-free piezoelectric ceramics (Na.47Bi.47Ba.06)1-xCaxTiO3 (x = 0, 0.01, 0.02, 0.03, 0.05, and 0.08, abbreviated as BNBTC/0, BNBTC/1, BNBTC/2, BNBTC/3, BNBTC/5, and BNBTC/8, respectively) were obtained using the solid-state reaction method. The structure, electric conductivity, and dielectric, ferroelectric, and piezoelectric properties of the Ca2+-doped (Na.47Bi.47Ba.06)TiO3 ceramics were thoroughly investigated. The ceramics sintered at 1200 °C exhibit dense microstructures, having relative densities higher than 96%. The X-ray diffraction results demonstrate that all ceramics have a pure perovskite structure. The mean grain sizes of the ceramics are related to the Ca2+ quantity. A small quantity of Ca2+ ions (x ≤ 0.03) improves the piezoelectric and ferroelectric properties of the samples. The dielectric behavior of the samples is sensitive to the Ca2+ content and electric poling. The results demonstrate that the electrical properties of the (Na.47Bi.47Ba.06)TiO3 lead-free ceramics can be well tuned by varying the Ca2+ quantity.

Enhanced electromechanical strain response in (Fe0.5Nb0.5)4+-modified Bi0.5(Na0.8K0.2)0.5TiO3 lead-free piezoelectric ceramics

By the traditional solid-state reaction method, Bi0.5(Na0.8K0.2)0.5Ti1−x(Fe0.5Nb0.5) x O3 (marked as BNKT-xFN; x = 0.00, 0.01, 0.02, 0.03 and 0.04) piezoelectric ceramics were fabricated, and the effects of FN substitution on the dielectric, ferroelectric, piezoelectric and electric field-induced strain performance were investigated. The relative dielectric permittivity and loss tangent reveal that the phase transition temperature between ferroelectric and ergodic relaxor phase is reduced from 90 °C to room temperature (RT), even below RT, with increasing FN content. Temperature dependence of polarization–electric field loops and strain-electric field curves exhibits that the ferroelectric order is disturbed gradually, and the ergodic relaxor phase forms with increasing FN content. A large unipolar strain of 0.42% and corresponding d33* (= Smax/Emax) of 642 pm/V for the sample with x = 0.04 are obtained under 6.5 kV/mm due to the phase transition from ergodic relaxor to ferroelectric. These results indicate that the (Fe0.5Nb0.5)4+ complex ion-modified BNKT-based ceramics would have great potentials for lead-free electromechanical actuator applications.

Influence of the sintering process on ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 lead-free piezoelectric ceramics

Fil: Camargo, Javier Eduardo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingenieria. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales; Argentina

Giant strain response in 2 mol% Nb-doped (Bi0.5Na0.4K0.1)TiO3 lead-free ceramics

A series of Nb-doped (Bi0.5Na0.4K0.1)TiO3 lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method. The X-ray diffraction patterns reveal a pure perovskite structure for all the samples. A giant strain of 0.34% is achieved at 2 mol% Nb-doping concentration, and the corresponding normalized strain $$d_{33}^*$$ reaches 625 pm V−1, which is one of the best results of the BNT-based ceramics. Complex ac impedance data indicate that only the bulk effect contributes to the resistivity. The compositionally induced disruption of long-range ferroelectric order and relaxor transition contributed to the pinched polarization loops as well as the large electric field-induced strain. The results indicate that appropriate Nb-dopant content can remarkably enhance the strain level of (Bi0.5Na0.4K0.1)TiO3 ceramics, making it a promising candidate for actuator applications.

An Investigation of Dielectric, Piezoelectric Properties and Microstructures of Bi0.5Na0.5TiO3-BaTiO3-Bi0.5K0.5TiO3 Lead-Free Piezoelectric Ceramics Doped with K2AlNbO5 Compound

The effect of K2AlNbO5 compound acting as both donor and accepter on the phase, microstructures and electrical properties of the 0.9362(Bi0.5Na0.5)TiO3-0.0637BaTiO3-0.02(Bi0.5K0.5)TiO3 [(1−x)(0.9163BNT-0.0637BT-0.02BKT)-x(K2AlNbO5)] (BNKBT-1000xKAN) ternary lead-free piezoelectric ceramics was systematically investigated. When doping content of K2AlNbO5 was varied from 0 to 0.009, the BNKBT-1000xKAN ceramics showed a single perovskite structure, and the phase structure transferred from a rhombohedral-tetragonal coexistent morphotropic phase boundaries zone to a tetragonal zone. The x-ray photoelectron spectroscopy analysis indicated that the chemical valence of the Nb and Al element are 5+ and 3+, respectively. Strong relaxor characteristics were revealed by the temperature-dependent dielectric properties of the ceramics. Typical square polarization-electric field (P-E) hysteresis loops were observed in the samples with doping content lower than 0.005. However, with further increasing the doping content (x = 0.007 and 0.009), round P-E hysteresis loops were observed due to the high conductivity of these samples. Moreover, when the doping content was less than 0.005, the ceramic samples exhibited good piezoelectric properties. Specially, when the doping content was 0.001, the piezoelectric constant d33 and electromechanical coupling coefficient kp of the sample were 197 pC/N and 22%, respectively. However, further addition would deteriorate both the dielectric and piezoelectric properties.

Characterization of acceptor-doped (Ba, Ca)TiO3 “hard” piezoelectric ceramics for high-power applications

Acceptor Mn or Co-doped Ba0.925Ca0.075TiO3 (abbreviated as BCT-Mn and BCT-Co) lead-free piezoelectric ceramics with high density and fine grains were synthesized by conventional solid-state reaction method. The phase structure and electrical properties of the ceramics were investigated. The acceptor-doped BCT ceramics were found to exhibit asymmetrical polarization-electric field hysteresis loops corresponding to the presence of an internal bias field Ei, indicating that the domain walls were pinned by preferentially oriented defect dipoles formed by the acceptors and oxygen vacancies. High mechanical quality factor Qm and low dielectric loss tanδ were obtained for the ceramics due to the strong internal bias field (Ei =4–5kV/cm). In particular, BCT-Mn ceramics exhibited the best properties, with mechanical quality factor Qm =1020, dielectric loss tanδ=0.2% and piezoelectric coefficient d33 =190 pC/N. Furthermore, the planar electromechanical coupling factor kp for BCT-Mn ceramics was found to be larger than 0.4 in the temperature range of 25°C to 75°C. These results indicate that the Mn-doped BCT lead-free ceramics material is a promising candidate for high-power piezoelectric applications.

The structure and electrical properties of CuO-doped (1-x)BZT-xBNT lead-free piezoelectric ceramics

ABSTRACTCuO-doped (1−x)Ba(Zr0.05Ti0.95)O3-x(Bi0.5Na0.5)TiO3 (BZT-xBNT, x = 0–0.5) lead-free piezoelectric ceramics were synthesized by the conventional solid state reaction method. Systematic investigation on the structures and electrical properties of the ceramics was carried out. The results demonstrated that pure perovskite structure was obtained for all the samples, while a phase transition from orthorhombic to rhombohedral structure occurred and the grain size decreased with increasing x. The ferroelectric polarization and Curie temperature were improved simultaneously with adding an appropriate content of BNT. As a result, the optimum remnant polarization (Pr) and piezoelectric coefficient (d33) were obtained at x = 0.4, reaching ∼13.4 µC/cm2 and ∼100 pC/N, respectively. Compared to pure BZT counterpart (TC∼100°C), this ceramic at x = 0.4 showed a higher TC, ∼175°C, and a moderate d33∼100 pC/N, thereby rendering it a promising candidate for piezoelectric applications.

Large strain response in (Mn,Sb)–modified (Bi0.5Na0.5)0.935Ba0.065TiO3 lead–free piezoelectric ceramics

Lead–free piezoelectric ceramics (Bi0.5Na0.5)0.935Ba0.065Ti1–x(Mn0.5Sb0.5)xO3 (BNBT6.5–xMS, x=0.005, 0.010, 0.015, 0.020) were prepared by conventional solid state reaction sintering technique. All ceramics present a pure perovskite phase structure, indicating that (Mn, Sb) has completely diffused into the BNBT6.5 lattice in the studied components. The addition of (Mn, Sb) disrupted the ferroelectric long–range order and promoted the electric field induced strain response. At x=0.015, a large electric field–induced unipolar strain of 0.48% (at an applied electric field of 80kV/cm) with normalized strain d33*(Smax/Emax) of 602pm/V are achieved. Temperature dependent measurements of both polarization and strain from room temperature to 120°C were also studied, and the results suggest that the origin of the large strain is due to a reversible field–induced non–polar relaxor phase to polar ferroelectric phase transformation.

Effect of texturing on polarization switching dynamics in ferroelectric ceramics

Highly (100),(001)-oriented (Ba0.85Ca0.15)TiO3 (BCT) lead-free piezoelectric ceramics were fabricated by the reactive templated grain growth method using a mixture of plate-like CaTiO3 and BaTiO3 particles. Piezoelectric properties of the ceramics with a high degree of texture were found to be considerably enhanced compared with the BCT ceramics with a low degree of texture. With increasing the Lotgering factor from 26% up to 94%, the piezoelectric properties develop towards the properties of a single crystal. The dynamics of polarization switching was studied over a broad time domain of 8 orders of magnitude and was found to strongly depend on the degree of orientation of the ceramics. Samples with a high degree of texture exhibited 2–3 orders of magnitude faster polarization switching, as compared with the ones with a low degree of texture. This was rationalized by means of the Inhomogeneous Field Mechanism model as a result of the narrower statistical distribution of the local electric field values in textured media, which promotes a more coherent switching process. The extracted microscopic parameters of switching revealed a decrease of the critical nucleus energy in systems with a high degree of texture providing more favorable switching conditions related to the enhanced ferroelectric properties of the textured material.

Broadband Near-Infrared Photoluminescence and Strong Visible Up-Conversion Emission in BaTiO3-(Na0.5Er0.5)TiO3 Lead-Free Piezoelectric Ceramics

For checking photoluminescence properties of BaTiO3-(Na0.5Er0.5)TiO3 lead-free piezoelectric ceramics, optical diffuse reflection spectra, visible up-conversion luminescence spectra, 1.55 μm near-infrared photoluminescence spectra, and optical temperature sensing performances under the excitation of 980 nm laser were investigated systematically. Broadband near-infrared (˜1.55 μm, FWHM˜90 nm) emission and strong visible up-conversion (˜550 nm) emission were observed under the 980 nm excitation in the ceramics at room temperature. Near-infrared emission and visible up-conversion emission became stronger with increasing (Na0.5Er0.5)TiO3 concentration below quenching point above which it will degrade. The optimal emission intensity was obtained when (Na0.5Er0.5)TiO3 content was 7 mol%. These ceramics with excellent ferro-/piezoelectric and photoluminescence properties may be useful for ultrasonic transducer, optical temperature sensor, optical amplifier, and other relative applications.

Large strain and relaxation behavior in CeO2 doped Bi0.487Na0.427K0.06Ba0.026TiO3 piezoceramics

xCeO2-doped Bi0.487Na0.427K0.06Ba0.026TiO3 lead-free piezoelectric ceramics (BNTC1000x, x=0, 0.3, 0.6, 0.8, 1.0, 1.2, 1.4wt%), were synthesized by the solid-state reaction method. XRD patterns showed that all BNTC1000x ceramics exhibit pure single perovskite phase. At the critical composition BNTC12, a large electric-field-induced strain of 0.39% with normalized strain (Smax/Emax) of 561pm/V was obtained under an electric field of 65kV/cm. The ferroelectric phase was fully poled with electric field, and depoled once the applied electric field was removed. During that cycle, the non-180°-domains repeated switching and back-switching and the large strain was induced. The relaxation behavior was involved in BNTC1000x ceramics and induced by oxygen vacancy migration. Besides, this behavior was more predominant in BNTC12 than in BNTC0.