Dielectric Properties and Impedance Spectroscopy of MnCO3‐Modified (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Lead‐Free Ceramics

A MnCO₃‐modified (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ system was synthesized by solid‐state reaction method. The phase structure, microstructure, electrical properties, and complex impedance were investigated in detail. The addition of small amount of MnCO₃ was quite effective to lower the sintering temperature. XRD analysis showed that the single perovskite phase was achieved in all compositions. XPS results demonstrated that the Mn ions were present in the mixed valence form of +2 and +4. The existence of Mn²⁺ ions gave rise to an increase in oxygen vacancies and suppressed the piezoelectric and ferroelectric properties of samples. The diffusive phase transition was enhanced while the Curie temperature was remained in the vicinity of 90°C. In addition, according to the impedance analysis, it was concluded that the dielectric relaxation behavior was non‐Debye type and the movements of singly ionized oxygen vacancies played an important role in the conduction behavior at higher temperatures.     

Chemical Synthesis,Sintering and Piezoelectric Properties of Ba0.85Ca0.15 Zr0.1Ti0.9O3 Lead‐Free Ceramics

The preparation of Ba_0.85Ca_0.15 Zr_0.1Ti_0.9O₃ (BCZT) powders by wet chemical methods has been investigated, and the powders used to explore relationships between the microstructure and piezoelectric properties (d₃₃ coefficient) of sintered BCZT ceramics. Sol–gel synthesis has been shown to be a successful method for the preparation of BCZT nanopowders with a pure tetragonal perovskite phase structure, specific surface area up to 21.8 m²/g and a mean particle size of 48 nm. These powders were suitable for the fabrication of dense BCZT ceramics with fine‐grain microstructures. The ceramics with the highest density of 95% theoretical density (TD) and grain size of 1.3 μm were prepared by uniaxial pressing followed by a two‐step sintering approach which contributed to the refinement of the BCTZ microstructure. A decrease in the grain size to 0.8–0.9 μm was achieved when samples were prepared using cold isostatic pressing. Using various sintering schedules, BCZT ceramics with broad range of grain sizes (0.8–60.5 μm) were prepared. The highest d₃₃ = 410.8 ± 13.2 pC/N was exhibited by ceramics prepared from sol–gel powder sintered at 1425°C, with the relative density of 89.6%TD and grain size of 36 μm.     

Phase Transition Behavior and Large Piezoelectricity Near the Morphotropic Phase Boundary of Lead‐Free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Ceramics

The phase transition behavior and piezoelectric properties of (Ba_1?xCa_x)(Zr_0.1Ti_0.9)O₃ and (Ba_0.85Ca_0.15)(Zr_yTi_1?y)O₃ ceramics were investigated in this work to find out the potential factors contributing to large piezoelectricity. It was found that the morphotropic phase boundary (MPB) of (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ ceramics was closely related to the presence of an intermediate phase (considered as orthorhombic phase in this work) between rhombohedral (R) and tetragonal (T) phases at a narrow region, which could be carefully adjusted by the temperature and contents of Ca and Zr in the composition. In addition, the maximum piezoelectric and electromechanical coupling coefficients (with d₃₃ = 572 pC/N and k_p = 0.57) were observed near the MPB region close to T phase side, which might be intimately related to the presence of the intermediate phase. This investigation yielded a new sight to understand the mechanism of enhanced piezoelectricity near the MPB.     

Effects of LiF on the Structure and Properties of Ba0.85Ca0.15Zr0.1Ti0.9O3 Lead‐Free Piezoelectric Ceramics

Preparation of Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) lead‐free piezoelectric ceramics with different amounts of LiF (BCZT‐xLiF) was done, and the effects of the LiF doping on the phase transition behavior and the electrical properties of the resulting ceramic were investigated. The experimental results showed that the polymorphic rhombohedral‐tetragonal phase transition temperature was found shifted toward room temperature with the Li doping. The study showed that BCZT lead‐free piezoelectric ceramic with improved performance properties at room temperature can be achieved by shifting the polymorphic phase transition point nearer room temperature through the addition of LiF.     

Enhanced Piezoelectric Properties of Praseodymium‐Modified Lead‐Free (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 Ceramics

The role of Pr₆O₁₁ addition on the structure, microstructure, electrical, and electromechanical properties of lead‐free (Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃ piezoelectric ceramics has been systemically investigated. Addition of praseodymium (Pr) results in improved ferroelectric and piezoelectric properties. XRD analysis revealed the co‐existence of rhombohedral (R) and tetragonal (T) phases at room temperature. High remanent polarization values (2P_r ~17 μC/cm²) and loop squareness of nearly 0.87 were obtained for the BCZT‐0.04 wt%Pr ceramic, along with high piezoelectric coefficient (d₃₃ = 435 pC/N) and transduction coefficient [(d₃₃·g₃₃) = 11589 × 10^?15 m²/N]. Results are correlated with the crystal structure and microstructure that significantly influence the ferroelectric and piezoelectric properties near the R–T phase transition point. This material seems to be especially suitable for energy harvesting applications, exhibiting outstanding figure of merit.     

Tuning of electrocaloric performance in (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 by induced relaxor-like behavior

Induced relaxor-like behavior is reported by addition of a sintering additive to the (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ solid solution. The effect of Bi₂O₃ sinter additive on microstructure is determined. The phase transition behavior is highlighted by dielectric permittivity measurements. The electrocaloric temperature change is directly measured and comparison with literature data is provided on basis of the material related cooling power. Addition of Bi₂O₃ drastically increases the temperature stability and an ultra-wide temperature range of over 100?K is achieved. The findings path a way to tune electrocaloric materials for optimization of properties for solid-state coolers based on the electrocaloric effect.     

Direct ink writing of macroporous lead-free piezoelectric Ba0.85Ca0.15Zr0.1Ti0.9O3

Direct ink writing (DIW) has become a widespread additive manufacturing technique for material engineering, but its application in lead-free Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ piezoelectric ceramics from aqueous systems has not been reported so far to our knowledge. The main obstacle is the high extent of hydrolysis reactions undergone by the starting powders when dispersed in water, hindering the attainment of stable water-based colloidal suspensions. This paper reports on the preparation of stable aqueous inks from a deagglomerated and surface-treated powder synthesized by solid-state reaction and on DIW of macroporous lead-free piezoelectrics. Based on zeta potential and rheological measurements, the optimal amounts of processing additives (dispersant, binder, and coagulating agent) were selected to transform the initial fluid suspension to a viscoelastic paste with sufficient stiffness and stability for the printing process. Dielectric and piezoelectric properties of samples sintered under different temperatures were also investigated.     

Fabrication and properties of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 ceramics and their multilayer piezoelectric actuators

The lead‐free ceramics with nominal composition (Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCTZ) were prepared by a conventional solid‐state reaction combined with a liquid precursor mixing method. Structural, dielectric, piezoelectric, and ferroelectric properties of the ceramics were systematically investigated. Excellent electrical properties of T_c ~ 101°C, tanδ ~ (0.003–0.05), k_p ~ 0.46, d₃₃ ~ 560 pC/N, P_s ~17 μC/cm² and a large strain of 0.43% were reproducibly obtained for the BCTZ ceramics. In addition, BCTZ‐based monolithic multilayer piezoelectric actuators were successfully fabricated by alternately laminating the claimed piezoelectric ceramics and internal‐binder. The actuators show large displacements under low driven voltage. These results highlight that the BCTZ ceramics are excellent candidate for multilayer piezoelectric devices.     

Ultrahigh and field-independent energy storage efficiency of (1-x)(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3-xBi(Mg0.5Ti0.5)O3 ceramics

Relaxor ferroelectrics are attracting an increasing interest in the application of pulse power systems due to their excellent energy storage performance. In this paper, the (1-x)(Ba_0·85Ca_0.15)(Zr_0·1Ti_0.9)O₃-xBi(Mg_0·5Ti_0.5)O₃ ((1-x)BCZT-xBMT, x ≤ 0.2) relaxor ceramics are prepared by the solid state method. The influence of BMT on the microstructure, dielectric and energy storage properties of the prepared ceramics is investigated. The XRD results show that the peak intensity of impurities (Bi₂O₃, TiO₂ and Ba₂Bi₄Ti₅O₁₈) is gradually stronger than that of BCZT phase with x increasing. Meanwhile, the grain size of (1-x)BCZT-xBMT ceramics gradually increases on account of the appearance of impurities Bi₂O₃. Influenced by the impurities and BMT, the dielectric constant of prepared ceramics gradually decreases with x increasing. A large W_rec value of 0.65 J/cm³ with an ultrahigh η value of 97.89% is achieved at x = 0.15 due to the high breakdown strength and slim P-E hysteresis loop. Meanwhile, the η is insensitive to the electric field. The ultrahigh η leads to lesser energy loss during the charge and discharge process. It makes the 0.85BCZT-0.15BMT ceramic more attractive in the application of pulse power systems.     

Phase Transition and Large Electrostrain in Lead‐Free Li‐Doped (Ba,Ca)(Ti,Zr)O3 Ceramics

Large piezoelectric effect is achieved in Li‐doped Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃(BCTZ) ceramics by use of tuning the phase boundaries. Rhombohedral–orthorhombic (R–O) and orthorhombic–tetragonal (O–T) multiphase coexistence is constructed in the ceramics by changing Li contents. The high piezoelectric constant d₃₃ (493 pC/N) and large electrostrain (dS_max/dE_max = 931 pm/V) have been observed in the Li‐doped (Ba, Ca)(Ti, Zr)O₃ ceramics at low sintering temperature (1350°C/2 h). The significant enhancement in materials properties is ascribed to the multiphase region around room temperature induced by Li‐doped effect.     

Electrical fatigue behavior of Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics under different oxygen concentrations

Fatigue degradation is a significant problem in piezo/ferroelectric materials and their commercial applications. The major causes of electrical fatigue degradation are a domain pinning effect and physical damage such as microcracking. This work reports the fatigue behavior of barium calcium zirconate titanate (Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃) under regular and low oxygen concentration silicone oil. Impedence analyzer and LCR meter are employed to analyzer the dielectric properties and it also revealed the relationship between activation energy and oxygen vacancy. X-ray diffraction, synchrotron X-ray absorption spectroscopy, and scanning electron microscope techniques were employed to study the local structural changes, defect development, physical damage and microcracking in the ceramics. FEFF-8.4 simulations were used to determine the oxygen vacancy creation. The study reveals the relationship of oxygen vacancy creation, domain wall pinning, microcracking and the fatigue behavior of the ferroelectric ceramic. The work investigated the dielectric and ferroelectric properties of BCZT ceramics intermes of applied electric field.     

Ba0.98Bi0.02(Ti0.9Zr0.1)1-xCuxO3陶瓷的介电弛豫特征

采用固相反应法制备Ba0.98Bi0.02(Ti0.9Zr0.1)1-xCuxO3(x=0,0.01,0.02,0.03,摩尔分数)陶瓷.X射线衍射分析结果表明:所有样品均为四方晶体结构,摩尔分数为2%的Cu2+能够完全溶入Ba0.98,Bi0.02(Ti0.9Zr0.1)03陶瓷晶格中.Ba0.98Bi0.02(Ti...     

Band gap narrowing and magnetic properties of transition-metal-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 lead-free ceramics

Transition metal (TM = Mn, Fe, Co, and Ni)-doped Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ (BCZT) lead-free ceramics with excellent optical and magnetic properties are synthesized via a solid-state reaction method. The effects of TM elements on the sintering, structure, optical, and magnetic properties of BCZT ceramics are investigated in detail. Structural phase transition from the coexistence of rhombohedral and tetragonal phases to a single rhombohedral phase is observed owing to grain refinement. A narrow band gap of 1.68 eV is achieved in the Co-doped BCZT. The optical absorption of TM-doped BCZT is enhanced, which is ascribed to the molecular orbital rearrangement caused by lattice distortion. Moreover the magnetic behaviors of TM-doped BCZT are observed. The Fe-doped BCZT presents the most evident ferromagnetism, resulting from the exchange coupling interaction between the Fe³⁺ ions and oxygen vacancies. These results provide additional insight into the use of TM-doped BCZT lead-free ferroelectric ceramics for various applications.     

Structure,electrical properties and reaction mechanism of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics synthesized by the molten salt method

Lead-free (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) ceramics with excellent electrical properties were successfully synthesized by a molten salt method (MSS). The submicron BCZT powders with pure perovskite phase were obtained by adjusting the KCl-NaCl content that was used as the eutectic salt. The effects of salt content and reaction temperature on the structure and properties of the BCZT materials were systematically investigated. Comparing with BCZT ceramics prepared by solid state method (SS), the reaction temperature of BCZT ceramics synthesized by MSS decreased approximately 200 °C. Moreover, BCZT ceramics sintered at 1360 °C with 50% eutectic salt showed the most outstanding electrical properties, which are as follows: d₃₃ = 604 pC/N, k_p = 57%, P_s = 17.11 µC/cm², P_r = 9.98 µC/cm², ε_m = 15872, ε_r = 2654 and tan δ = 0.013. In addition, this work revealed a possible reaction course processes and mechanism about MSS. The results provide a new design to optimize the performance of BCZT lead-free piezoelectric ceramics.     

Investigation of ferroelectric,piezoelectric and mechanically coupled properties of lead-free (Ba0.85Ca0.15) (Zr0.1Ti0.9)O3 ceramics

Lead-free piezoelectric ceramic (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) has been synthesised by solid-state sintering method and the effect of grain size on ferroelectric, piezoelectric, dielectric, mechanical and piezo-electro-mechanical properties was systematically studied. The compacted powders were sintered at three temperatures i.e. 1450°°C, 1500°C and 1550°C for an optimised duration of 5?h and they have exhibited well resolved morphotropic phase boundary with an average grain size ranging from 10 to 25?µm. Enhanced piezoelectric charge, d₃₃ ～ 560 pC/N and voltage, g₃₃ ～ 14.3?mV?m/N coefficients were obtained for the 1450°C sintered BCZT sample. A maximum strain of around ～0.14% was obtained which is comparable to that of lead-based piezoelectrics. Variation of relative permittivity with temperature revealed that the curves are independent of frequency, indicating the typical relaxor ferroelectric nature of the samples. A systematic study on cyclic loading was performed to evaluate piezo-electro-mechanical coefficients at different loads which showed hysteresis behaviour. High value of elastic modulus (E) and hardness (H) i.e. 262.7?±?38.1?GPa and 13.7?±?1.7?GPa were exhibited by samples sintered at 1450°C, which is higher than that of BCZT synthesised by wet-chemical methods. The results are discussed.     

Piezo/pyro/photo-catalysis activities in Ba0.85Ca0.15(Ti0.9Zr0.1)1-xFexO3 ceramics

Ba_0.85Ca_0.15(Ti_0.9Zr_0.1)_1-xFe_xO₃ (x = 0, 0.5, and 1%) ceramics were studied for piezocatalysis, photocatalysis, and pyrocatalysis using dye degradation in the simulated wastewater. The effect of electrical poling was also performed and found a significant impact of poling on all three catalytic reactions. Fe decreased the optical bandgap of Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ (BCZTO) to the visible region. Bandgap for x = 0, 0.005, and 0.01 was found to be 3.14 eV, 2.75 eV, and 2.61 eV, respectively. Interestingly, visible light photocatalytic activity was observed after Fe inclusion in BCZTO lattice. These compositions have also demonstrated dye degradation under ultrasonication (piezocatalytsis) and during temporal temperature change (pyrocatalysis). Results indicate promising multicatalysis in BCZTO ceramics which can be tuned using Fe substitution.     

Magnetoelectric coupling studies in lead-free multiferroic (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3−(Ni0.7Zn0.3)Fe2O4 ceramic composites

Lead-free multiferroic 3–0 type particulate composites with a composition (1?x)(Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃) – x(Ni_0.7Zn_0.3Fe₂O₄) [(1?x)BCZT – xNZFO with 0 ≤ x ≤ 100 at%] were prepared using solid state reaction method. Structural and microstructural analysis using XRD, FESEM and Raman techniques confirmed the phase formation of the ferroelectric (BCZT) and magnetostrictive (NZFO) phases without any detectable presence of impurity phases. Rietveld refinement of the XRD data revealed a tetragonal (P4mm) and a cubic structure (Fd$\stackrel{￣}{3}$m) for the BCZT and NZFO phases, respectively. Elemental compositions of the constituent phases were assessed by EDS and XPS analyses. Electrical, magnetic, and magnetoelectric (ME) measurements were performed. The composites exhibit typical well-saturated magnetic hysteresis (M?H) loops at room temperature, having very low coercive field ($H_C$) values, indicating their soft ferromagnetic behavior. Various parameters extracted from the M?H curves including $H_C$, magneto-crystalline anisotropy, squareness, and magnetization were found to depend on x. Frequency dependence of capacitance and admittance exhibited a resonance behavior corresponding to the radial mode of the electromechanical resonance (EMR). ME coefficients were studied in both longitudinal (${\alpha }_{\text{E}33}$) and transverse (${\alpha }_{\text{E}31}$) modes. The highest coupling coefficients, ${\alpha }_{\text{E}31}$ ～14.5 mV/Oe.cm and ${\alpha }_{\text{E}33}$ ～13 mV/Oe.cm were obtained for composite with 50 at% NZF at off-resonance frequency of 1 kHz. At the EMR frequency of 314 kHz, the ${\alpha }_{\text{E}31}$ value in 0.5BCZT-0.5NZFO composite enhanced enormously to ～5.5 V/Oe.cm. The studies conclude that x = 0.5 is an optimum atomic fraction of NZFO in the particulate composite for maximum ME coupling.     

On the formation mechanism of Ba0.85Ca0.15Zr0.1Ti0.9O3 thin films by aqueous chemical solution deposition

Here we report on the development of an environmentally friendly, simple and robust aqueous chemical solution route for the fabrication of Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) thin films. Using a stable aqueous precursor solution, thin films were prepared by spin coating and the impact of thermal processing on the microstructure and phase purity of the thin film was revealed by X-ray diffraction and transmission electron microscopy. We find, that barium oxycarbonate formation during the pyrolysis plays a key role in the formation of dense, homogeneous single phase BCZT films. The formation of barium oxycarbonate leads to undesirable segregation of cations, resulting in barium depletion on the BCZT grain boundaries and occurrence of a secondary phase (CaZrTi₂O₇). Based on this insight the thermal processing was optimized and dense, oriented and single-phase BCZT films were fabricated by combining a low pyrolysis temperature with rapid heating to the annealing temperature.     

Ca含量对(Ba1-xCax)(Ti0.9Zr0.1)O3无铅压电陶瓷性能的影响

采用传统的固相法制备(Ba1-xCax)(Ti0.9Zr0.1)O3(简称BCTZ)无铅压电陶瓷.借助扫描电镜(SEM)和X射线衍射仪(XRD)等测试方法研究了Ca含量对所制备BCTZ无铅压电陶瓷显微结构和压电介电性能的影响.结果表明:随着Ca含量的增加,(Ba1-xCax)(Ti0.9Zr0.1)O3无铅压电陶瓷的晶粒尺寸先增大后减小,所制备的BCTZ陶瓷的物相都是钙钛矿结构,没有杂相;随着Ca含量的增加,BCTZ陶瓷压电常数(d33),介电常数(εr),机电耦合系数(kp)分别先增加后降低,而介质损耗(tanδ)先减小后增大.当Ca含量(x)为0.15mol时,在1450℃烧结制得的(Ba1-xCax)(Ti0.9Zr0.1)O3无铅压电陶瓷性能最佳:压电常数(d33)为363pC/N,机电耦合系数(kp)为39.63％,介电常数(εr)为4184,介质损耗(tanδ)为1.08％.     

Structural,Optical, and Piezoelectric Response of Lead‐Free Ba0.95Mg0.05Zr0.1Ti0.9O3 Nanocrystalline Powder

Nanocrystalline powders of Ba_1?xMg_xZr_0.1Ti_0.9O₃ (x = 0.025–0.1) were synthesized via citrate assisted sol–gel method. Interestingly, the one with x = 0.05 in the system Ba_1?xMg_xZr_0.1Ti_0.9O₃ exhibited fairly good piezoelectric response aside from the other physical properties. The phase and structural confirmation of synthesized powder was established by X‐ray powder diffraction (XRD) and Raman Spectroscopic techniques. Two distinct Raman bands i.e., 303 and 723 cm^?1 characteristic of tetragonal phase were observed. Thermogravimetric analysis (TGA) was performed to evaluate the phase decomposition of the as‐synthesized Ba_0.95Mg_0.05Zr_0.1Ti_0.9O₃ sample as a function of temperature. The average crystallite size associated with Ba_0.95Mg_0.05Zr_0.1Ti_0.9O₃ was calculated using Scherrer formula based on the XRD data and was found to be 25 nm. However, Scanning and Transmission Electron Microscopy studies revealed the average crystallite size to be in the range of 30–40 nm, respectively. Kubelka–Munk function was employed to determine the optical band gap of these nanocrystallites. A piezoelectric response of 26 pm/V was observed for Ba_0.95Mg_0.05Zr_0.1Ti_0.9O₃ nanocrystal by Piezoresponse Force Microscopy (PFM) technique. Photoluminescence (PL) study carried out on these nanocrystals exhibited a blue emission (470 nm) at room temperature.