一步法合成的2.0%Sm-0.25Pb(Mg1/3Nb2/3)O3-0.75Pb(Zr1-xTix)O3压电陶瓷的压电性能

通常采用两步合成法制备铌镁酸铅-锆钛酸铅(Pb(Mg_1/3Nb_2/3)O₃-Pb(Zr, Ti)O₃,PMN-PZT)压电陶瓷,即先合成MgNb₂O₆前驱体。工业生产中,两步法生产效率相对较低,成本高,并影响产品性能的一致性。本工作通过高效及低成本的一步合成法,研制了高致密度和高压电性能的2.0%(摩尔分数,下同)Sm-0.25Pb(Mg_1/3Nb_2/3)O₃-0.75Pb(Zr_1-xTi_x)O₃(Sm-PMN-PZT)压电陶瓷。在x=0.52～0.53范围内,构建了三方相、四方相(R-T)共存的准同型相界(MPBs);Sm³⁺的引入增强了局域结构异质性,外电场下铁电相变的势垒较低,即自由能曲线的曲率最小,压电性能得到优化。当x=0.525时,陶瓷具有最优的综合电学性能,压电系数d₃₃     

新型铁电晶体铌镥酸铅-钛酸铅的生长与性能

采用顶部籽晶法生长了一系列不同组分的高居里温度铌镥酸铅-钛酸铅[(1-x)Pb(Lu_1/2Nb_1/2)O₃-xPbTiO₃ (PLN-xPT)]铁电晶体。该晶体在三方相区域表现出典型的介电弛豫特性, 不同组分的晶体表现出了较高的居里温度; 基于介电和结构测试结果, 得到了该体系的低温二元体系相图, 在相图中存在一个准同型相界区域(MPB), 其组分位于x = 0.49~0.51; 利用偏光显微镜分析晶体电畴结构得到和X射线粉末衍射测试结果吻合的相结构; 电学性能测试结果表明不同组分的晶体性能差异较大。组分位于MPB附近的晶体表现出优异的压电性能, 如x = 0.49时, 居里温度T_c = 360℃, 压电常数d₃₃ > 1600 pC/N。处于MPB附近的晶体存在较大的矫顽E_c >10kV/cm, 一些组分晶体的三方–四方相变温度T_RT > 200℃。结果表明高的居里温度及优异的压电性能使二元铌镥酸铅-钛酸铅晶体具有更大的温度应用范围及更广阔的应用前景。     

BaZrO3掺杂对(K0.49Na0.51)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3无铅压电陶瓷的结构与电性能的影响

采用固相反应法制备了(K_0.49Na_0.51)_0.98Li_0.02(Nb_0.77Ta_0.18Sb_0.05)O₃-xBaZrO₃ (NKNLST-xBZ, x = 0~0.020 mol)无铅压电陶瓷, 系统研究了BaZrO₃的掺杂量对陶瓷的压电、介电、机电和铁电性能的影响。结果表明: 随着BaZrO₃掺杂量x的增加, 陶瓷的晶体结构由正交相向四方相转变, 在x=0.005~0.008区间出现正交相与四方相两相共存的区域, 在此区域内陶瓷的晶粒变得细小且均匀, 介电损耗tanδ大幅降低, 压电常数d₃₃和平面机电耦合系数k_p增加。该体系陶瓷的介电常数ε T 33 /ε0则随着BaZrO₃的增加持续增加, 相变温度则向低温方向移动。当x=0.005时, 该组成陶瓷具有最佳的综合性能: 压电常数d33=372 pC/N, 平面机电耦合系数kp=47.2%, 介电损耗tanδ=3.1%, 以及较高的介电常数ε^T₃₃ /ε₀=1470和居里温度T_c=208℃。     

Er3+掺杂弛豫铁电材料PMNT的单晶生长与性能表征

按照0.71Pb(Mg_1/3Nb_2/3)O₃-0.26PbTiO₃-0.03Pb(Er_1/2Nb_1/2)O₃化学式所示组分比例, 采用分步高温固相反应合成出Er³⁺掺杂PMNT多晶, 通过熔体坩埚下降法生长出尺寸φ25 mm×100 mm的Er³⁺掺杂PMNT晶体, Er³⁺离子以三元固溶体组元方式被掺杂进入钙钛矿相铁电体晶格; 测试了Er³⁺掺杂PMNT晶片的介电、压电与铁电性能以及上转换发光性能。结果表明, Er³⁺掺杂PMNT晶体呈现跟三方相纯PMNT晶体相近的介电、压电与铁电性能; 在980 nm激发光作用下, 该掺杂晶体呈现出Er³⁺离子特有的较强上转换荧光发射, 并且极化后掺杂晶体的上转换发光强度得到增强。     

铌镁酸铋-钛酸铅压电陶瓷准同型相界附近的性能和相变温度研究

利用传统固相烧结法制备了Bi(Mg_2/3Nb_1/3)O₃-PbTiO₃(BMN-PT)压电陶瓷, 分析了不同PbTiO₃含量对BMN-PT压电陶瓷的晶体结构、介电、压电及铁电性能的影响. XRD结果表明: 合成的BMN-PT陶瓷具有纯钙钛矿结构, 并且在PbTiO₃含量为x=0.60时, 其组分的XRD图谱在衍射角2θ=45°出现明显的分峰, 说明该组分相结构中存在三方和四方相的共存. 压电铁电性能显示, BMN-0.60PT有最大的压电常数d₃₃(~170pC/N)和平面机电耦合系数k_p(0.35), 最小的矫顽场E_c(29.4 kV/cm)及最大的剩余极化P_r(31.4 μC/cm²). 确定了BMN-PT压电陶瓷的准同型相界(MPB)为PbTiO₃含量x=0.60的组分. 介电系数温谱表明介电系数峰值温度(Tm)随着PbTiO₃含量的增大而升高, MPB组分的Tm约为276℃.     

(1-x)K0.48Na0.52NbO3-xBi0.45Nd0.05(Na0.92Li0.08)0.5ZrO3无铅压电陶瓷相结构及压电性能

为了在获得较高压电性能的同时又不大大降低陶瓷的居里温度(T_C), 设计和制备了Bi_0.45Nd_0.05(Na_0.92Li_0.08)_0.5ZrO₃改性的K_0.48Na_0.52NbO₃系无铅压电陶瓷((1-x)KNN-xBNNLZ), 研究了BNNLZ含量对KNN基无铅压电陶瓷相结构和电学性能的影响。研究结果表明, 所有陶瓷样品均具有较高的居里温度T_C(>300℃)。随着BNNLZ含量的增加, 陶瓷的正交-四方相变温度(T_O-T)不断向低温方向移动, 而三方-正交相变温度(T_R-O)不断向高温方向移动, 最终在陶瓷中形成了三方-四方(R-T)共存相, R-T共存相处于0.05<x<0.07范围。BNNLZ的加入引起陶瓷相结构的演化改变导致压电常数(d₃₃ )、介电常数(ε_r )、剩余极化强度 (P_r )和机电耦合系数(k_p )都先增大后减小, 当x=0.06时陶瓷具有最佳压电性能: d₃₃=313 pC/N, k_p=42%, P_r=25.48 μC/cm², ε_r=1353, tanδ=2.5%, T_C=327℃。     

CaxSr1-xBi2Nb2O9无铅压电陶瓷制备及其高温稳定性研究

采用传统固相法制备了Ca_xSr_1-xBi₂Nb₂O₉ (x=0、0.10、0.25、0.40)无铅压电陶瓷, 研究了Ca²⁺掺杂量对其微观结构、电学性能及其高温稳定性的影响。掺入Ca²⁺并未改变SrBi₂Nb₂O₉陶瓷的晶体结构; 随着Ca²⁺掺杂量的增加, 陶瓷晶粒由片状向长条状转变; 陶瓷的矫顽场(E_c)下降, 剩余极化强度(P_r)先增大后减小; 陶瓷的居里温度由450℃升高到672℃。当x=0.10时, 陶瓷具有较好的综合性能: 2P_r=14.8 μC/cm², d₃₃=22 pC/N, T_c=488℃; 当退火温度达到400℃时, 压电常数d₃₃仍达到20 pC/N, 说明该材料具有较好的温度稳定性, 可以在400℃的高温环境中应用。     

Bi(Mg_(1/2)Ti_(1/2))O_3-PbTiO_3压电陶瓷体系介电与居里温度特性研究

采用传统固相法工艺制备了(1-x)Bi(Mg1/2Ti1/2)O3-x Pb Ti O3(BMT-x PT,0.34≤x≤0.44)陶瓷。研究发现,随着PT含量增加,试样结构由三方相逐渐转变为四方相结构,当0.36x0.40时,试样结构处于准同型相界(MPB)区。研究表明BMT组元是一种具有非铁电体特征的组分,随着PT含量减少,BMT-PT体系的居里温度减小,介电峰变得越来越不明显。通过研究BMT-PT体系组分与居里温度(TC)的关系可以看出:(1)PT含量为0.34~0.44时,TC随BMT含量变化实验值和Stringer的经验值差异较小,变化趋势一致;(2)BMT-PT体系居里温度最大值可能在x=0.73的附近,其居里温度最大值TC max约为550℃。     

1-3型水泥基压电复合材料的制备及性能

采用切割-浇注法, 以硫铝酸盐水泥为基体, 制备了1-3型水泥基压电复合材料。详细阐述了1-3型水泥基压电复合材料的制备过程; 研究了0.375Pb(Mg_1/3Nb_2/3)O₃-0.375PbTiO₃-0.25PbZrO₃压电陶瓷柱的宽厚比w/t对1-3型水泥基压电复合材料的压电性能、 介电性能和声阻抗的影响。结果表明: 压电陶瓷柱的宽厚比w/t对1-3型水泥基压电复合材料性能有很大影响, 随着w/t的增加, 其压电应变常数d₃₃、 机电耦合系数K_p与K_t、 机械品质因数Q_m、 介电常数ε_r和介电损耗tanδ均随着w/t的增加而减小, 而压电电压常数g₃₃值几乎不受w/t的影响。在压电陶瓷体积分数仅为22.72%的条件下, 调节压电陶瓷柱的宽厚比w/t至0.130, 可使复合材料的声阻抗与混凝土的声阻抗十分接近, 从而有效地解决了智能材料在土木工程中的声阻抗相容性问题。      

In2O3/InNbO4复合材料的热电性能研究

In₂O₃作为一种良好的光电和气敏材料, 因高温下具有优异的热电性能在热电领域也获得广泛关注。本研究通过固相反应法结合放电等离子烧结(SPS)成功将原位自生的InNbO₄第二相引入到In₂O₃基体中, 优化了块体样品的制备工艺。同时, InNbO₄改善了样品的电输运性能, 使载流子浓度明显提高, 在1023 K时电导率最高可达1548 S·cm^-1, 高于大多数元素掺杂的样品。其中, 0.998In₂O₃/0.002InNbO₄样品的热电性能测试表明, 在1023 K时, 其功率因子可达到0.67 mW·m^-1·K^-2, 热电优值(ZT)达到最高值0.187。综上所述, 通过在In₂O₃中原位复合InNbO₄第二相可以很好地改善In₂O₃基热电陶瓷的电性能, 进而调控其高温热电性能。     

Present and future of piezoelectric single crystals and the importance of B-site cations for high piezoelectric response

High quality piezoelectric single crystals, such as Pb(Zn_1/3 Nb_2/3)O₃-PbTiO₃ (PZNT) and Pb(Mg _1/3Nb_2/3)O₃-PbTiO₃ (PMNT), have been investigated, and, because their piezoelectric properties are greatly superior to those of Pb(Zr_1-xTi_x)O₃ (PZT) ceramics, they have been used for certain transducer applications since the late 1990s. The present situation for these relaxor-PT (lead titanate) single crystals is summarized. In this review, some possible high Tc > 200°C single crystals are also introduced. Single crystals of Pb(In_1/2Nb_1/2)O₃-PbTiO₃ (PINT) binary system and Pb(Mg_1/3Nb_2/3)O₃ -Pb(Sc_1/2Nb_1/2)O₃-PbTiO₃ (PSMNT) tertiary system have been synthesized, and their electrical properties are reported. In addition, a novel guiding principle for discovering excellent piezoelectric materials, namely the presence of low molecular mass B-site ions that can enter the lead-perovskite Pb(B'B")O₃ structure, is introduced     

Characteristics of relaxor-based piezoelectric single crystals forultrasonic transducers

For ultrasonic transducers, piezoelectric ceramics offer a range of dielectric constants (K~1000-5000), large piezoelectric coefficients (d_ij~200-700 pC/N), and high electromechanical coupling (k _t≃50%, k₃₃≃75%). For several decades, the material of choice has been polycrystalline ceramics based on the solid solution Pb(Zr_1-xB_2x)O₃ (PZT), compositionally engineered near the morphotropic phase boundary (MPB). The search for alternative MPB systems has led researchers to revisit relaxor-based materials with the general formula, Pb(B₁,B₂)O₃ (B₁:Zn²⁺ , Mg²⁺, Sc³⁺, Ni²⁺..., B₂ :Nb⁵⁺ Ta⁵⁺...). There are some claims of superior dielectric and piezoelectric performance compared to that of PZT materials. However, when the properties are examined relative to transition temperature (T₃), these differences are not significant. In the single crystal form, however, Relaxor-PT materials, represented by Pb(Zn_1/3Nb_2/3)O₃-PbTiO ₃ (PZN-PT), Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) have been found to exhibit longitudinal coupling coefficients (k₃₃)>90%, thickness coupling (k_t)>83%, dielectric constants ranging from 1000 to 5000 with low dielectric loss <1%, and exceptional piezoelectric coefficients d₃₃>2000 pC/N, the later promising for high energy density actuators. For single crystal piezoelectrics to become the next generation material of ultrasonic transducers, further investigation in crystal growth, device fabrication and testing are required     

Effects of growth conditions on the domain structure and dielectric properties of (1 − x)Pb(Sc1/2Nb1/2)O3–xPbTiO3 single crystals

The studies of the (1 − x)Pb(Sc_1/2Nb_1/2)O₃–xPbTiO₃ (PSN–PT) single crystals reveal that the chemical and physical properties of the materials are affected by the growth conditions. By the measurements of the dielectric constant as a function of temperature upon cooling, it is found that crystals grown from the same charged stoichiometric composition (x = 0.425), but under different flux environments (i.e. the composition of flux and the flux to PSN–PT ratios are varied), show anomalies (i.e. phase transitions) at different temperatures. This phenomenon is attributed to the complex local chemical structure of the PSN–PT solid solution single crystals with B-site random occupancy of three different cations (Sc³⁺, Nb⁵⁺ and Ti⁴⁺). The dielectric and domain structure of the PSN–PT crystals with composition near the morphotropic phase boundary (MPB) are investigated, showing much more complex situations compared with Pb(Sc_1/2Nb_1/2)O₃.     

Conduction analysis of Li2O doped 0.2[Pb(Mg1/3Nb2/3)]–0.8[PbTiO3–PbZrO3] ceramics fabricated by columbite precursor method

We have fabricated 0.2Pb(Mg_1/3Nb_2/3)O₃–0.8Pb(Zr_0.475Ti_0.525)O₃ [PMN–PZT] ceramics doped with various amounts of Li₂O (0, 0.05, 0.1, 0.2, 0.3 wt.%) using the columbite precursor method. The effects of Li-doping on the conduction behavior of PMN–PZT ceramics are discussed in relation to the low frequency dielectric dispersion and frequency domain measurement. The Li-doped PMN–PZT ceramics sintered at 950 °C showed a sufficient densification with large dielectric constant and low dielectric loss. The incorporation of Li⁺ ion in PMN–PZT ceramics led to an appreciable reduction in electrical conductivity and further enhanced the ferroelectric and piezoelectric properties. The activation energies of PMN–PZT + xLi₂O (x = 0, 0.05, 0.1, 0.2, 0.3 wt.%) ceramics calculated from ac conductivity measurement using the Arrhenius relation were 1.05, 1.25, 1.27, 1.38 and 1.41 eV, respectively. The conduction behavior is examined in the low frequency and high temperature region and the results are discussed in detail through crystal defect mechanism.     

Preparation and characterization of yBiGaO/sub 3/-(1-x-y)BiScOs/sub 3-x/PbTiO/sub 3/ piezoelectric ceramics

The ternary system of j/BiGaO₃-(1-x-y) BiScO₃-xPbTiO₃ (BGS-PT) ceramics was prepared by using conventional mixing oxide processing. X-ray diffraction analysis revealed that the BGS-PT ceramics showed the perovskite structure. The Curie temperature (T_C) of BGS-PT ceramics was found to increase with increasing BiGaO₃ content. However, a larger BiGaO₃ content led to sharply decreased piezoelectric properties, and the secondary phase was formed in the BGS-PT system. BGS-PT ceramics with x = 0.56, y = 0.19 showed a high Curie temperature T_C and a large piezoelectric constant d₃₃ of 501degC and 152 pC/N, respectively. The high T_C of BGS-PT ceramics with usable piezoelectric properties suggests future high-temperature applications.     

Phase-transition temperatures and piezoelectric properties of (Bi/sub 1/2/Li/sub 1/2/)TiO/sub 3/-(Bi/sub 1/2/K/sub 1/2/)TiO/sub 3/ lead-free ferroelectric ceramics

The phase-transition temperatures and piezoelectric properties of x(Bi_1/2Na_1/2)TiO_3-y(Bi_1/2Li_1/2)TiO_3-z(Bi_1/2K_1/2)TiO₃ [x + y + z = 1] (abbreviated as BNLKT100y-100z) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T_d, rhombohedral-tetragonal phase transition temperature T_R-T, and dielectric-maximum temperature T_m were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100y-100z show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor &33, piezoelectric constant d₃₃ and T_d of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171degC, and 0.590, 190 pC/N, and 115degC, respectively. In addition, the relationship between d₃₃ and T_d of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high T_d and high d₃₃, the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d₃₃ and T_d of BNLKT4-28 were 135 pC/N and 218degC, respectively. Moreover, this study revealed that the variation of Td is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

High electrical properties of W-additive Mn-modified PZT–PMS–PZN ceramics for high power piezoelectric transformers

The ceramics were prepared successfully by the addition of WO₃ to the Mn-modified Pb(Zr_0.52Ti_0.48)O₃–Pb(Mn_1/3Sb_2/3)O₃–Pb(Zn_1/3Nb_2/3)O₃ (PZT–PMS–PZN) for high power piezoelectric transformers application. XRD analysis indicated that the ceramics were mainly composed of a tetragonal phase in the range of 0–1.0 wt.% WO₃ addition. The grain size of the ceramics significantly decreased from 10.0 to 2.9 μm by addition of WO₃. Moreover, the addition of WO₃ promoted densification of the ceramics and increased mechanical quality factor (Q_m), planar coupling factor (K_p) and piezoelectric constant (d₃₃) kept high values, whereas, dielectric loss (tan δ) was low. Δf (=f_a − f_r) slightly changed when WO₃ addition was above 0.5 wt.%. The ceramics with 0.6 wt.% WO₃ addition, sintered at 1150 °C showed the optimized piezoelectric and dielectric properties with Q_m of 1852, K_p of 0.58, d₃₃ of 243 pC/N and tan δ of 0.0050. The ceramics are promising candidates for high power piezoelectric transformers application.