Properties of Low‐Temperature Sintering PNN–PMW–PSN–PZT Piezoelectric Ceramics with Ba(Cu1/2W1/2)O3 Sintering Aids

Piezoelectric ceramics Pb(Ni_1/3Nb_2/3)O₃–Pb(Mg_1/2W_1/2)O₃–Pb(Sb_1/2Nb_1/2)O₃–Pb(Zr_0.39Ti_0.61)O₃ with Ba(Cu_1/2W_1/2)O₃ sintering aids were fabricated using economical industrial oxide powders and their piezoelectric, dielectric, and ferroelectric properties were investigated in order to develop low‐temperature sintering ceramics for multilayer piezoelectric actuators. A quadratic formula and the Curie–Weiss law reveal that the ceramics are typical displacive‐type ferroelectric relaxors. The ceramics sintered as low as 900°C have good piezoelectric properties of d₃₃ = 551 pC/N, k_p = 0.52, ε_r = 3583, tgδ = 0.02, and T_C = 161°C, which is much promising to manufacture multilayer piezoelectric transducers.     

Lead-free 0.7BiFeO3-0.3BaTiO3 high-temperature piezoelectric ceramics: Nano-BaTiO3 raw powder leading to a distinct reaction path and enhanced electrical properties

Herein, nano-BaTiO₃/Bi₂O₃/Fe₂O₃ and BaCO₃/TiO₂/Bi₂O₃/Fe₂O₃ were respectively used to prepare 0.7BiFeO₃-0.3BaTiO₃ (0.7BF-0.3BT) ceramics by conventional solid-state method and clarify the reaction path, phase structure, microstructure, ferroelectric, and piezoelectric properties. 0.7BF-0.3BT ceramic using nano-BaTiO₃ with cubic phase (C_BT) undergoes the formation of rhombohedral α-phase (R_α) and the transition from R_α and C_BT to rhombohedral β-phase (R_β) and pseudo-cubic (PC) phases, while the counterpart using BaCO₃/TiO₂ directly generates R_β and PC. Nano-BaTiO₃ can decrease pores and oxygen vacancies in the resultant ceramics comparing to BaCO₃/TiO₂, which is due to an inhibited decomposition of R_α and a weaker reduction of Fe³⁺ to Fe²⁺, leading to increased density and reduced leakage current density. Benefitting from a proper phase ratio, increased density and reduced leakage current density, the enhanced piezoelectric properties d₃₃?=?210?pC/N, k_p?=?0.34, P_r?=?31.2?μC/cm² and T_C?=?514?°C are obtained in 0.7BF-0.3BT ceramic using nano-BaTiO₃. Our work reveals the importance of raw materials and the potential of BF-BT as a high-temperature lead-free piezoelectric ceramic material.     

Properties and structures of nonstoichiometric (K,Na)NbO3‐based lead‐free ceramics

The 0.968[(K_0.48Na_0.52)]Nb_0.95+xSb_0.05O₃–0.032(Bi_0.5Na_0.5)ZrO₃ [KNN_xS–BNZ] lead‐free ceramics with nonstoichiometric niobium ion were fabricated via conventional solid‐state sintering technique and their piezoelectric, dielectric and ferroelectric properties were investigated. When x = 0.010, enhanced piezoelectric properties (d₃₃ ≈ 421 pC/N and k_p ≈ 0.47) were obtained due to the construction of rhombohendral—tetragonal phase boundary near room temperature. The KNN_xS–BNZ ceramics possesses enhanced Curie temperature (T_c) with improved piezoelectric constant. A large d₃₃ of ~421 pC/N and a high T_c ~256°C can be simultaneously induced in the ceramics with x = 0.010. Especially, good thermal stability was observed in a broad temperature range. The results indicated that our work could benefit development of KNN‐based ceramics and widen their application range.     

High-temperature BiFeO3–PbTiO3-Ba(Zr,Ti)O3 ternary ceramics with excellent piezoelectricity

Ternary ceramics of (0.87−x)BiFeO₃–xPbTiO₃–0.13Ba(Zr_0.5Ti_0.5)O₃ (BF–xPT–0.13BZT, 0.27 ≤ x ≤ 0.37) were prepared by the traditional solid state reaction methods. X-ray diffraction results display that BF-xPT-0.13BZT ternary ceramics of x ≥ 0.29 exhibit the perovskite structure with dominant tetragonal (T) phases mixed with a small amount of rhombohedral (R) phases. Scanning electron microscopy (SEM) images reveal that the average grain size of BF-xPT-0.13BZT ternary ceramics is in a range of 10–11 μm, increasing first and then decreasing with the increase of PbTiO₃ (PT) content. The low tanδ of about 0.015 and high Curie temperature T_c of above 450°C were obtained for BF-xPT-0.13BZT ternary ceramics. Moreover, the fluctuation of piezoelectric coefficient d₃₃ is less than ±10% over a broad temperature range of 30°C–400°C. BF-xPT-0.13BZT ternary ceramics for x = 0.33 possess the maximum T_c and d₃₃ of 470°C and 320 pC/N respectively, with the room temperature resistivity of about 10¹¹ Ω·cm. These results indicate that BF-xPT-0.13BZT ternary ceramics for x = 0.33 with both excellent piezoelectric properties and high Curie temperature have promising applications in high-temperature piezoelectric devices.     

高温压电陶瓷研究进展

评述了碱金属铌酸盐、钨青铜结构、铋层状结构和钙钛矿结构等高温压电陶瓷体系的结构和性能,重点介绍了复合钙钛矿固溶体系Bi(Me)O3-PbTiO3的研究进展.总结了影响压电陶瓷Curie温度的影响因素.提出了高温压电陶瓷今后的研究方向:一方面根据容差因子和Curie温度的关系开发新的高温压电体系:另一方面通过掺杂改性和工艺优化增加钙钛矿结构的稳定性并提高其性能.     

铋层状结构铁电材料的性能与改性研究

铋层状材料具有优良的铁电性能,本文介绍了铋层状材料的结构及其特点,并且综述了其铁电性能(疲劳性能、压电性能)的研究现状、存在的问题.介绍了几种铋层状结构材料改性的工艺措施(热铸法、模板定向生长技术、掺杂).     

New methodology for determining the dielectric constant of a piezoelectric material at the resonance frequency range

A new methodology is proposed to measure the dielectric constant and loss of a piezoelectric at the resonance frequency range based on the burst excitation method. Using a k₃₁ type soft PZT rectangular specimen, we investigated the “force” and “voltage” factors carefully under the short‐ and open‐circuit conditions of the burst method, in terms of the ratio of the ring‐down current and voltage with the plate end vibration velocity and the displacement, and their phase lags. We provide the obtained material properties, including loss parameters, in particular, dielectric properties at the resonance frequency range.     

(Na1-xKx)0.5Bi0.5TiO3系无铅压电陶瓷的电学性能研究

利用固相法制备了(Na1-xKx)0.5Bi0.5TiO3系压电陶瓷,所得陶瓷样品介电损耗tanδ最大不超过5%,最好的压电常数d33=153pC/N,平面机电耦合系数kp=0.299,它们分别出现在x=0.22和0.20处。同时通过对其介电性能的测试,表明该样品具有弛豫铁电性,是典型的弛豫铁电体。     

Effect of point defects on Curie temperature of lithium niobate

The effect of point defects on the Curie temperature (T_c) of LiNbO₃ (LN) was investigated by combining T_c measurements with an analysis of the defect structures of LN doped with impurities having various valences. The data show that T_c of congruent LN increases with the impurity concentration up to around 3 and 2 mol% for divalent and trivalent impurities, respectively, whereas it decreases continuously with increased concentrations of tetravalent impurities. These T_c variations were examined with respect to the defect structures of impurity‐doped LN, which are expressed in the form chemical formulae using Kröger‐Vink notation. The defect structures of divalent and trivalent impurity‐doped LN are and , respectively (Nb_Li: Nb at Li sites; V_Li: vacancies at Li sites, M_Li: impurities at Li sites, and Li/Nb = the congruent ratio). The defect structure in the case of tetravalent impurities is . Analyses of the defect structures indicated that the Nb_Li concentration decreases with divalent or trivalent impurity doping, which increases T_c. In contrast, the Nb_Li concentration increases with tetravalent impurity doping, which decreases T_c. In addition, the divalent or trivalent impurity concentrations at which the Nb_Li concentration becomes zero were found to correspond to the concentrations at which T_c is maximized, suggesting that T_c of LN depends on the Nb_Li concentration.     

Effect of degree of crystallographic texture on ferro‐ and piezoelectric properties of Ba0.85Ca0.15TiO3 piezoceramics

Crystallographic texturing is a promising approach to reduce the performance gap between randomly oriented polycrystalline piezoelectrics and perfectly oriented single crystals. Here, the influence of the degree of crystallographic texture on the electromechanical properties and their temperature stability of the lead‐free perovskite ferroelectric Ba_0.85Ca_0.15TiO₃ is investigated. Samples with a broad range of (100),(001) crystallographic texture (Lotgering factor 26%‐83%) were prepared by the reactive templated grain growth method. Crystallographic and microstructural analysis have been carried out using X‐ray diffraction and scanning electron microscopy, while the temperature‐dependent electromechanical properties were characterized by dielectric, piezoelectric, polarization, and strain measurements. It was revealed that the total bipolar strain and the coercive field are linearly dependent on the Lotgering factor. The total bipolar strain increased by 80%, whereas the coercive field decreased by 18% due to crystallographic texturing. Likewise, the temperature stability of the electromechanical properties of the samples was found to be dependent on the degree of texture. A sample with a high degree of texture exhibited a Curie temperature of 117°C, which is 21% higher compared to a counterpart with a low degree of texture. This was related to chemical inhomogeneity and a modified internal mechanical stress state.     

Effects of temperature and electric field on upconversion luminescence in Er3+‐Yb3+ codoped Ba0.8Sr0.2TiO3 ferroelectric ceramics

Optical and electrical properties of 1%Er³⁺ and different Yb³⁺ content (1ExY) codoped Ba_0.8Sr_0.2TiO₃ (BST) ferroelectric ceramics fabricated by the solid‐phase reaction were investigated. Under 980 nm pump condition, two green emission bands at 525 and 549 nm wavelength corresponding to, ²H_11/2→⁴I_15/2 and ²S_3/2→⁴I_15/2 transitions, and two red emission bands at 655 and 668 nm wavelength attributed to ⁴F_9/2→⁴I_15/2 transition are observed. The temperature‐sensing behaviors, calculated by the intensity ratio I₅₂₅/I₅₄₉ suggested that, the maximum sensitivity of the green emission of the 1E8Y‐BST ceramics is 1.07×10^?2 K‐1 at 293 K. Furthermore, the maximum sensitivity of 1E6Y‐BST and 1E11Y‐BST ceramics were obtained around the Curie temperature. The fluorescence lifetime of 1E8Y‐BST ceramics for ²H_11/2 level and ²S_3/2 level shortened with the increase in the temperatures. Moreover, the upconversion (UC) luminescence intensity of 1E8Y‐BST decreased with the increase in the external electric field and had a mutation at the coercive electric field (E_c) of about 1.24 kV/cm, which revealed that the electric field had influence on the UC luminescence.     

Thermal stability and electric‐field‐induced strain behaviors for PIN‐PSN‐PT piezoelectric ceramics

Pb (In_1/2Nb_1/2) O₃‐Pb (Sc_1/2Nb_1/2) O₃‐PbTiO₃ (PIN‐PSN‐PT) ternary ceramics with compositions near morphotropic phase boundary (MPB) were fabricated by solid‐state‐sintering process. Dielectric and piezoelectric properties of xPIN‐yPSN‐zPT (x = 0.19, 0.23 and z = 0.365, 0.385) ceramics were investigated as a function of temperature, showing high T_r‐t and T_c on the order of 160 ~ 200°C and 280 ~ 290°C, respectively. The xPIN‐yPSN‐0.365PT (x = 0.19 and 0.23) ceramics do not depolarize at the temperature up to 200°C, showing a better thermal stability when compared to the state‐of‐the‐art relaxor‐PbTiO₃ systems. A slight variation (<9%) of k_p, k_t, and k₃₃ was observed in the temperature range of 25°C‐160°C for xPIN‐yPSN‐0.385PT (x = 0.19 and 0.23) ceramics. Rayleigh analysis was employed to quantify the contribution of domain wall motion to piezoelectric response, where the domain wall contribution was found to increase with composition approaching MPB for PIN‐PSN‐PT system.     

不同晶粒取向钛酸铋陶瓷的铁电和压电性能

用固相烧结工艺制备了不同取向率(I)的Bi4Ti3O12(BTO)多晶陶瓷样品.在相同的烧结温度(1140℃),BTO样品的I随烧结时间(2～20h)的增加出现了先升高后降低的变化趋势,最大值达89.9%.样品的铁电和压电性能均与样品的I有关,在α/(b)择优取向的BTO样品的铁电和压电性能都随样品I的升高而改善,其2倍剩余极化强度(Pr)和压电系数(d33)分别达到53.4μC/cm2和22.2pC/N;c取向样品的2Pr和d33则随着取向率的升高而降低.     

Ba掺杂对Pb（Zr,Ti,Sb）O3压电陶瓷Curie温度与压电性能的影响

用传统固相法制备了组成为0.98Pb1.0–xBaxTi0.48Zr0.52O3–0.02PbSbO3(x=0.18～0.24)的Ba掺杂Pb(Zr,Ti,Sb)O3(PSZT)压电陶瓷。通过X射线衍射和Raman光谱研究了Ba掺杂PSZT陶瓷的结构,并测量和分析了Ba掺杂对PSZT压电陶瓷的Curie温度和压电性能的影响。结果表明:Ba掺杂影响PSZT陶瓷中四方相和三方相的转化过程、两相比例、晶粒大小并导致四方相的晶格畸变。随Ba含量(x)从0.18增加到0.24,PSZT陶瓷的Curie温度从189℃几乎线性下降到141℃;当Ba掺杂量为0.22时,PSZT陶瓷的Curie温度为156℃,压电应变常数d33为578pC/N,机电耦合系数Kp为0.63,机械品质因数Qm为37.3。     

高Curie温度(1-2x)PbNb2O6-xSrTiO3-xTiO2压电陶瓷

采用传统电子陶瓷的制备方法制备了(1-2x)PbNb2O6-xSrTiO3-xTiO2(x=0.005～0.025)高Curie温度(θc)压电陶瓷.X射线衍射分析表明:所有样品在1 250℃保温2h烧结均形成铁电性的斜方钨青铜型结构(tungsteu bronze structure,TB).相对介电常数-温度(εr-θ)曲线表明:该体系具有高的θc(500～560℃).测试了不同掺杂量对陶瓷介电和压电性能的影响,发现材料的θc、压电常数(d33)和机电耦合系数(κp)随着x值的增加先增加后降低.当x=0.02时,陶瓷的d33达到最大值,为83pC/N,θc为550℃,κp达33.4%,材料的介电常数Εθ33/ε0为217,为组成的最优配方.