Na0.5K0.5NbO3-LiTaO3无铅压电陶瓷的研究

采用传统固相反应合成法制备(1–x)Na0.5K0.5NbO3-xLiTaO3无铅压电陶瓷,研究了LiTaO3对Na0.5K0.5NbO3材料晶体结构和压电性能的影响。结果表明:随着LiTaO3含量的增加,材料逐渐由斜方相向四方相过渡。当x<0.06时,材料为斜方相;当x>0.06时,材料为四方相;并发现有未知相结构的Ta2O5存在;材料在x=0.06处为准同型相界,该组分材料具有良好的压电性能:d33=134~151 pC.N-1,kp=30%~38%,Qm=153,Nd=3 181 Hz.m.     

铌酸钾钠陶瓷的低温制备及其介电性能分析

以柠檬酸为配位剂与金属离子配合,水作为溶剂,乙二醇为酯化剂,通过聚合物前驱体法制备(K0.5Na0.5)NbO3陶瓷.采用XRD和失重-差热(TG-DSC)研究了(K0.5Na0.5)NbO3晶相的形成过程,用SEM对所制得粉体和陶瓷的表面形貌进行了分析.结果表明,凝胶前驱体在加热过程中先反应生成NaNbO3和K2Nb8O21,然后二者固相反应形成K0.5Na0.5NbO3.所得粉体的粒径约为φ400 nm,呈柱状.1 100℃所得陶瓷较致密,在0.1 MHz时的介电常数和介电损耗分别为405和0.036.所制备陶瓷在183℃和375℃时发生相变,其中375℃对应的相变为铁电相变.     

锂掺杂对K0.5Na0.5NbO3无铅压电陶瓷电性能的影响

采用固相法制备了Li掺杂K0.5Na0.5NbO3无铅压电陶瓷,即K0.5Na0.5NbO3+x/2%Li2CO3(KNN-xL)。研究了不同Li摩尔分数(x分别为0,0.25,0.50,0.75,1.00,1.50)样品的物相组成、显微结构及电性能。结果表明,室温下所有样品都具有正交相的钙钛矿结构。随着Li摩尔分数的增加,样品的压电常数d33、平面机电耦合系数kp、机械品质因数Qm及密度ρ都先升高后降低,介电损耗tanδ普遍比未掺杂的低,当x=0.5时综合性能达到最优,即d33=122pC/N,kp=41%,Qm=115,εr=548,tanδ=0.022,ρ=4.32g/cm3。另外正交到四方相变温度逐渐降低,居里温度逐渐升高。     

(1-x)Na0.5K0.5NbO3-xBiNiO3无铅压电陶瓷的制备与性能

利用传统固相合成法制备了(1-x)Na0.5K0.5NbO3-xBiNiO3 ( (1-x)NKN- xBN) 无铅压电陶瓷.采用X-射线衍射(XRD)、扫描电镜(SEM)等手段对其显微结构与性能进行研究.结果表明,该体系所研究组分范围内均能形成典型的ABO3型钙钛矿结构,在x=0.006～0.008间存在准同型相界(MPB).体系主要压电性能在x＝0.008左右获得优化,其压电常数d33和机电耦合系数kp 均达到极大值(分别为135 pC/N和44%), 机械品质因数Qm为122,正交-四方转变温度TO-T和居里温度TC分别为155 ℃和385 ℃.     

Microstructure and Electrical Properties of K0.5Na0.5NbO3-LiSbO3-BiFeO3-x %molZnO Lead-Free Piezoelectric Ceramics

Lead-free piezoelectric ceramics {0.996[(0.95(K_0.5Na_0.5)NbO₃-0.05LiSbO₃]-0.004BiFeO₃}-xmol%ZnO were prepared through a conventional ceramics sintering technique. The effect of ZnO content on structure, microstructure, and piezoelectric properties of KNN-LS-BF ceramics was investigated. The results reveal that ZnO as a sintering aid is very effective in promoting sinterability and electrical properties of the ceramics sintered at a low temperature of 1,020 °C. The ceramics show a single-perovskite structure with predominant tetragonal phase, and coexistence of orthorhombic and tetragonal phases is observed for x = 2.5–3.0. The addition of ZnO causes abnormal grain growth. A dense microstructure is also obtained at x = 2.0 because the relative density reaches up to 94.6 %. The morphotropic phase boundary and dense microstructure lead to significant enhancement of the piezoelectric properties. The ceramic with x = 1.5 exhibits optimum electrical properties as follows: d ₃₃ = 280 pC/N, k _p = 46 %, Q _m = 40.8, P _r = 25 μC/cm², E _c = 1.2 kV/mm, and T _c = 340 °C.     

Effect of the Addition of B2O3 on the Density, Microstructure, Dielectric, Piezoelectric and Ferroelectric Properties of K0.5Na0.5NbO3 Ceramics

Boron oxide (B₂O₃) addition to pre-reacted K_0.5Na_0.5NbO₃ (KNN) powders facilitated swift densification at relatively low sintering temperatures which was believed to be a key to minimize potassium and sodium loss. The base KNN powder was synthesized via solid-state reaction route. The different amounts (0.1–1 wt%) of B₂O₃ were-added, and ceramics were sintered at different temperatures and durations to optimize the amount of B₂O₃ needed to obtain KNN pellets with highest possible density and grain size. The 0.1 wt% B₂O₃-added KNN ceramics sintered at 1,100 °C for 1 h exhibited higher density (97 %). Scanning electron microscopy studies confirmed an increase in average grain size with increasing B₂O₃ content at appropriate temperature of sintering and duration. The B₂O₃-added KNN ceramics exhibited improved dielectric and piezoelectric properties at room temperature. For instance, 0.1 wt% B₂O₃-added KNN ceramic exhibited d ₃₃ value of 116 pC/N which is much higher than that of pure KNN ceramics. Interestingly, all the B₂O₃-added (0.1–1 wt%) KNN ceramics exhibited polarization–electric field (P vs. E) hysteresis loops at room temperature. The remnant polarization (P _r) and coercive field (E _c) values are dependent on the B₂O₃ content and crystallite size.     

Bi0.5(Na1-x-yKxLiy)0.5TiO3陶瓷的介电性能与微观结构

利用传统陶瓷工艺制备了新型的Bi0.5(Na1-x-yKxLiy)0.5TiO3无铅压电陶瓷,研究了陶瓷的介电性能和微观结构。研究结果表明,介电常数εr和介质损耗tgδ在K含量为0.20~0.25(摩尔分数)时达到最大值,且随Li含量的增加而增大;介温曲线表明,Bi0.5(Na1-x-yKxLiy)0.5TiO3陶瓷在110~210℃之间出现介质损耗峰,在300~350℃附近出现比较平坦的介电常数峰;陶瓷的最佳烧结条件为1 100~1 150℃,2~3 h;陶瓷晶粒有规则的几何外形,晶粒尺寸为1.2~2.5 m;Li含量越高,陶瓷的烧结温度越低;K促进了晶粒特定方向的生长。     

Dielectric Properties and Defect Structure of Bi—doped SrTiO3 Ceramics

The dielectric properties of ceramics with composition of (Sr1-xBix) TiO3 x/2( where x=0.05-0.70) were measured at frequency of 1 MHz.The experimental results indicate that the dielectric properties of (Sr1-xBix)TiO3 x/2 system are greatly varied with an increase of the stoichiometric amounts of Bi2O3.The relative permittivity of the solid solutions is high, and the dissipation factor is low.The positron annihilation technique(PAT) was adopted to study the defect structure.An explanation of the dielectric properties of Bi-doped SrTiO3 ceramics has been suggested in terms of electron-compensation and vacancy or defect-compensation mechanisms and space-charge polarization mechanism.     

聚合物前驱体法制备铌酸钾钠薄膜

以加入和不加入草酸铵两种方法制备氢氧化铌。以碳酸钾、碳酸钠和制得的氢氧化铌为原料,柠檬酸为螯合剂,乙二醇为酯化剂,通过聚合物前驱体法在SiO2/Si基板上制备了铌酸钾钠(KNN)薄膜。研究了草酸铵的添加和不同退火温度对KNN薄膜性质的影响。结果显示:在pH=7.5,金属阳离子与柠檬酸摩尔比为1:3,柠檬酸与乙二醇的摩尔比为2:1时,可以获得均匀稳定的KNN前驱体溶胶。草酸铵的加入优化了薄膜的性能;随着退火温度的增加,薄膜的致密度越来越高。退火温度在850℃时,薄膜结晶性相对较好;900℃退火处理后,薄膜晶粒有定向生长趋势。     

Li0.025Na0.975NbO3晶体的介电和铁电性质

观察了Li0.025Na0.975NbO3晶体的电滞回线，并研究了它在400℃以下的介电温谱和室温时500MHz以下的介电频谱。其介电温谱的峰值在升温和降温时分别出现在380℃和365℃，有明显的热滞，因此其相变属于一级相变。Li0.025Na0.975NbO3晶体在500MHz附近可能存在介电弛豫。     

银掺杂Bi0.5(Na0.825K0.175)0.5TiO3陶瓷的结构与性能

采用传统固相法制备了无铅压电陶瓷Bi0.5(NA0.825K0.175)0.5TiO3+x%Ag2O(BNKTA-x,质量分数x=0,0.1,0.3,0.5,0.7,1.0,1.5),利用XRD、SEM等测试技术分析表征了该体系陶瓷的结构、压电与介电性能.XRD分析表明,在1 175℃/2 h烧结条件下,当Ag的质量分数低于1.0%时,陶瓷呈单一相的钙钛矿结构.所有陶瓷晶粒大多成四方晶形,晶界明显,表面致密度高,Ag的引入促进了陶瓷晶粒的生长.另外,加入Ag后,陶瓷样品气孔率降低,当Ag的质量分数在0.3%附近时陶瓷的致密性最好.BNKTA-x体系陶瓷具有较好的电学性能:压电常数d33=147 pC/N,机电耦合系数kp=0.31,介电常数εr=1 059,介电损耗tanδ=0.029,机械品质因数Qm=247.     

Piezoelectric and Dielectric Properties of Nonstoichiometric (Na0.5K0.5)0.97(Nb0.90Ta0.1)O3 Ceramics Doped with MnO2

MnO₂-added nonstoichiometric (K_0.5Na_0.5)_0.97(Nb_0.90Ta_0.1)O₃ lead-free piezoelectric ceramics were prepared by conventional sintering processes. X-ray diffraction data show that MnO₂ diffuses into the lattice of (K_0.5Na_0.5)_0.97 (Nb_0.90Ta_0.1)O₃ ceramics and forms a pure perovskite structure with orthorhombic symmetry. The microstructure of the samples showed that a certain amount of MnO₂ addition could improve the crystalline grain growth. The addition of a small amount of MnO₂ increased the mechanical quality factor (Q _m), piezoelectric constant (d ₃₃), and electromechanical coupling factor (k _p). At room temperature, (K_0.5Na_0.5)_0.97(Nb_0.90Ta_0.1)O₃ ceramics doped with 0.4?mol% MnO₂ showed piezoelectric properties suitable for low-loss piezoelectric actuator applications: k _p?=?0.43, Q _m?=?1212, d ₃₃?=?112?pC/N, and tan?δ?=?0.023.     

水热辅助聚合物前驱体法制备铌酸钾钠薄膜

以自制氢氧化铌、化学试剂碳酸钾、碳酸钠为原料,柠檬酸(CA)为螯合剂,乙二醇(EG)为酯化剂,采用水热辅助聚合物前驱体法在SiO2/Si基板上制备了铌酸钾钠(KNN)薄膜.研究了CA和EG用量对溶胶性能的影响,衬底和退火温度对薄膜的影响.结果表明,当n(CA):n(金属离子)=3:1,n(CA):n(EG)=1:2时,可获得稳定性好的溶胶.以水热处理过的Si片为基板得到的薄膜结晶性和致密性都有了很大的改善;随着退火温度的升高,薄膜的结晶性越来越好,所得薄膜粒径均匀,无裂纹,有定向生长的趋势.     

铌酸钠钾基无铅压电陶瓷的相结构与压电性能

采用传统固相反应合成法制备了结构致密的(1-x)Na0.5K0.5NbO3-xLiTaO3(KNNT)无铅压电陶瓷,研究了LiTaO3对Na0.5K0.5NbO3材料晶体结构和压电性能的影响。结果表明,随着LiTaO3含量的增加,材料的钙钛矿结构由斜方相向四方相转变,KNNT材料的准同型相界位于0.04 mol相似文献   

金属有机盐热分解法制备铌酸钾钠无铅压电薄膜

选用乙醇铌、乙酸钾、乙酸钠为原料,通过金属有机盐热分解法制备了Na0.5K0.5NbO3(NKN)无铅压电薄膜。研究了不同退火温度对NKN薄膜的晶体结构和形貌的影响。结果表明:当退火温度低于500℃时,所制NKN薄膜为无定形结构。650℃制备的NKN薄膜具有(100)晶面生长的择优取向;该薄膜的表面致密,颗粒尺寸分布均匀,10kHz的相对介电常数为258,介电损耗为0.05。该薄膜具有铁电体典型的电滞回线,剩余极化强度(Pr)和矫顽场强(EC)分别为3.45×10–6C/cm2和160×103V/cm。     

Electrooptic ferroelectric Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films

We report on waveguiding and electrooptic properties of epitaxial Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films grown by radio-frequency magnetron sputtering on Al/sub 2/O/sub 3/(11_02) single crystal substrates. High optical waveguiding performance has been demonstrated in infrared and visible light. The in-plane electrooptic effect has been recorded in transmission using a transverse geometry. At dc fields, the effective linear electrooptic coefficient was determined to 28 pm/V, which is promising for modulator applications.     

微波合成铌酸钾钠系无铅压电陶瓷粉体的研究

分别采用微波加热法和电加热法合成了固相0.94(K0.5Na0.5)NbO3-0.06LiNbO3无铅压电陶瓷粉体,对比研究了两种不同合成工艺及其对陶瓷粉体相组成和微观形貌的影响.结果表明,较常规的电加热合成工艺,微波法可使合成温度降低达200 ℃,合成时间缩短至电热合成的1/20,可制备出形状规则,大小均匀,团聚较少的粉体,是一种具有很好应用前景的材料合成方法.     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的介电压电性能

研究了(Na1-xKx)0.5Bi0.5TiO3体系无铅压电陶瓷的介电、压电性能，通过XRD分析，发现随着x的增加，陶瓷的晶体结构由三方相逐渐转变为四方相，x=0．16～0．20范围内具有三方和四方共存相结构，为该体系的准同型相界(MPB)，材料在MPB附近具有最佳的压电性能．测试了陶瓷的介电温谱，表明该体系陶瓷为弛豫型铁电体，电滞回线表明陶瓷在升温过程中发生铁电-反铁电-顺电相变．