纳米Na0.5Bi0.5TiO3粉体的水热合成研究

以Bi(NO3)3·5H2O、Ti(OC4H9)4为原料,研究和分析了水热条件下Na0.5Bi0.5TiO3(BNT)晶体生长和形成的影响因素.结果表明,在反应温度为160～180℃,保温时间为4～16h,NaOH浓度为4～12mol/L的条件下可制备出高纯度的纳米Na0.5Bi0.5TiO3粉体,其颗粒尺寸约为15～60nm.     

Bi0.5Na0.5TiO3系无铅压电陶瓷的研究

概述了Bi0.5Na0.5TiO3(BNT)基无铅压电陶瓷的研究近况。第二组元化合物的加入能使BNT陶瓷的矫顽场降低，使BNT基陶瓷的压电性能得到了提高。根据BNT基无铅压电陶瓷的A位和B位原子的原子量、离子半径和电负性，研究了BNT基压电陶瓷的性能与这些参数的关系。     

Structure and Electric Properties of （1-x）（Bi1/2Na1/2） TiO3-xBaTiO3 Systems

The structural, dielectric and piezoelectric properties of （1-x）（Bi1/2Na1/2） TiO3-xBaTiO3 ceramics were investigated for the compositional range, x=0.02, 0.04, 0.06, 0.08, 0.10. The samples were synthesized by a conventional solid-state reaction technique. All compositions show a single perovskite structure, and X-ray powder diffraction patterns can be indexed using a rhombohedral structure. Lattice constants and lattice distortion increase while the amount of BaTiO3 increases. The X-ray diffraction results show the morphotropic phase boundary （MPB） of （1-x）（Bi1/2Na12） TiO3-xBaTiO3 exists in near x=0.06-0.08. Temperature dependence of dielectric constant eT33/ε0 measurement reveals that all compositions experience one structural phase and two ferroelectric phases transition below 400℃： rhombohedral （or rhombohedral plus tetragonal） ferroelectric phase ←→ tetragonal antiferroelectric phase ←→ tetragonal paraelectric phase. Relaxor behaviors exist in the course of ferroelectric to antiferroelectric phase transition. Dielectric and piezoelectric properties are enhanced in the MPB range for （ 1-x）（Bi1/2Na1/2）TiO3-xBaTiO3.     

(Bi1/2Na1/2)1-xBaxTiO3系无铅压电陶瓷的现状

综述了(Bi1／2Na1/2)1-xBaxTiO3系无铅压电陶瓷的最新研究进展。简述了A位非化学计量改性及几种较成功的掺杂改性方法。将A位掺杂(如La^3 )、B位掺杂(如Co^3 、Nb^5 )以及综合掺杂(如Ce^3 、Ce^4 )的优缺点和掺杂机理进行了归类比较。解释了各系统中相应掺杂引起性能变化的原因，为进一步开展无铅压电陶瓷的研究提供参考。     

（0.82-x）Bi0.5Na0.82Ti O3-0.18Bi0.5K0.18TiO3-xBiFeO3（x=0.01-0.07）无铅压电陶瓷的制备及其电学性能的研究

采用传统的固相烧结法于1120℃烧结2 h得到（0.82-x）Bi0.5Na0.82Ti O3-0.18Bi0.5K0.18TiO3-xBiFeO3（x=0.01-0.07）无铅压电陶瓷,并对该体系陶瓷的微观结构和电学性能进行了研究。结果表明,BiFeO3的引入量x为0.01-0.07时,样品均为具有MPB准同型相界（三方相和四方相共存）的钙钛矿结构。BiFeO3的引入使陶瓷的晶粒度略有增加;当x=0.03时,样品达到最大致密度。为97.7%;陶瓷的压电常数d33随BiFeO3的引入而降低。陶瓷的相对介电常数εr和居里温度随BiFeO3的引入而明显增大,在x=0.03时达到最大值。     

Bi1/2Na1/2TiO3-Bi1/2Na1/2(Nb2/3Zn1/3)O3-BaTiO3无铅陶瓷压电介电性能

采用传统陶瓷制备方法,制备出新型无铅压电陶瓷,并对该体系无铅陶瓷的相结构、介电和压电性能进行了研究.结果表明:所研究的组成均能够形成纯钙钛矿(ABO3)型固溶体;随着BaTiO3含量的增加,压电系数d33先增大后减小.同时陶瓷材料的介电常数-温度曲线显示该体系材料具有明显的弛豫铁电体特征.     

K0.5Bi0.5TiO3:ZnO无铅铁电复合陶瓷的退极化行为

为了抑制K_(0.5)Bi_(0.5)TiO_3的退极化现象,提高铁电性能,以K_2CO_3、TiO_2、Bi_2O_3及ZnO为原料,通过二步固相法合成无铅铁电复合陶瓷K_(0.5)Bi_(0.5)TiO_3:ZnO(KBT:ZnO).通过X射线衍射、扫描电子显微镜、铁电和介电测试分析了复合陶瓷的微观结构和介电行为.结果表明:KBT中引入20%(物质的量百分数)的ZnO后,复合陶瓷中生成了第三相Zn2TiO_4,同时,KBT的极化能力及其铁电行为得到改善.阻抗测试表明复合铁电陶瓷内部只存在一种导电机制,即电子电导.特别是ZnO的引入抑制了KBT由正常铁电体向弛豫铁电体的相转变,对KBT的应用和研究有着重要的作用.     

(Bi_(1/2)Na_(1/2))_(1-x)Ba_xTiO_3系无铅压电陶瓷的现状

综述了(Bi1/2Na1/2)1-xBaxTiO3系无铅压电陶瓷的最新研究进展。简述了A位非化学计量改性及几种较成功的掺杂改性方法。将A位掺杂(如La3+)、B位掺杂(如Co3+、Nb5+)以及综合掺杂(如Ce3+、Ce4+)的优缺点和掺杂机理进行了归类比较。解释了各系统中相应掺杂引起性能变化的原因,为进一步开展无铅压电陶瓷的研究提供参考。     

Microstructure, crystalline phase and electrical properties of Li0.06（Na0.5K0.5）0.94Nb（1-2x/5）MgxO3 lead-free piezoelectric ceramics

MgO-modified Li0.06(Na0.5K0.5)0.94NbO3(L6NKN) lead-free piezoelectric ceramics were synthesized by normal sintering at a relatively low temperature of 1000°C.The crystalline phase,microstructure,and electrical properties of the ceramics were investigated with a special emphasis on the influence of MgO content.The addition of MgO effectively improves the sinterability of the L6NKN ceramics.X-ray diffraction analysis indicates that the morphotropic phase boundary(MPB) separating orthorhombic and tetragonal ph...     

Effect of doped Mn on piezoelectric properties of （Na0.5Bi0.5 ）0.92 Ba0.08 TiO3 lead-free ceramics

Piezoelectric ceramics (Na0.5Bi0.5)0.92Ba0.05TiO3 x%MnCO3(BNBT-Mn, x=0-1.6,mass fraction)were synthesized by conventional solid state reaction. The results show that when the addition of MnCO3 is 0-1.4%, BNBT-Mn ceramics exhibit a single-phase perovskite structure. With the increase of content of MnCO3, piezoelectric constant and electromechanical coupling factor increase rapidly when x is lower than 0.3. Then they both decrease when x is in the range of 0.3 and 1.6. When x=0.3, piezoelectric constant and electromechanical coupling factor reach the maximum value of 160 pC/N and 58.5% respectively, which can improve the temperature stability of BNBT-Mn.     

Structure and Electrical Properties of （Na0.5Bi0.5）0.94Ba0.06TiO3 Ceramicwith0.5wt% of MnO

The structure and electrical properties of （Na0.5Bi0.5）0.94Ba0.06TiO3 ceramic doped with 0.5 wt% of MnO were investigated in comparison with those of （Na0.5Bi0.5）0.94Ba0.06TiO3 ceramic. It was ascertained that the MnO addition did not cause remarkable change in crystal structure and microstructure. The MnO addition mainly displayed a hard effect on the electrical properties, an increase of coercive field （E） and mechanical quality factor （Qm） together with a decrease of dielectric constant （εr） and piezoelectric constant （d33）. An enhancement of electromechanical coupling factor （kp） with the MnO addition was obtained too. An essential relation between the piezoelectric properties and ferroelectric nature of the ceramics was detected. It was found that the piezoelectric properties of the ceramics highly depended on the corporative contribution of remanent polarization （Pt） and coercive field.     

Synthesis and Piezoelectric Properties of Lead-free (Bi_(0.5)Na_ (0.5))_ 1-x(Ba_aSr_b)_xTiO_3 Ceramics

planarelectromechanicalcouplingfactor;piezoelectricchargeconstant1Introduction Leadoxide basedpiezoelectricceramics,suchasPb(Ti,Zr)O3(PZT),arenowwidelyusedinvariousappli cationssuchastransducers,filters,oscillatorsandactua torsbecauseoftheirsuperiorpiezoe…     

Ce4+及La3+掺杂对(Bi0.5Na0.5) Ba0.06TiO3 陶瓷压电性能的影响

采用固相法制备工艺制备了质量分数CeO2(0-0.6%)和La2O3(0-1.3%)掺杂的(Bi0.5Na0.5)0.94Ba0.06TiO3(BNBT6)无铅压电陶瓷.研究了合成产物的晶体结构、压电性能以及压电常数温度稳定系数.结果表明:所有组成均呈三方结构的钙钛矿型固溶体特征;当CeO2掺杂量为质量分数0.4%、La2O3掺杂量为质量分数1.0%时,陶瓷具有较好的压电性能,与纯BNBT6相比,分别提高了12%和15%;2种掺杂离子均能够改善陶瓷材料压电性能的温度稳定性.     

Effect of Li content on the microstructure and properties of lead-free piezoelectric （K0.5Na0.5）1-xLixNbO3 ceramics prepared by SPS

Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of （K0.5Na0.5）NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the （K0.5Na0.5）1-xLixNbO3 ceramics.     

Dielectric Properties of Ag（Nb1-xTax）O3 and Bi2O3 Doped Ag（Nb1-xTax）O3 Ceramics

Dielectric properties of Ag（Nb1-xTa）O3 and Bi2O3 doped Ag（Nb1-xTax）O3 solid solutions were investigated. The results show that with the increase of Ta content （x）, the sintering temperature increased, and the dielectric loss （tanδ） and the temperature coefficient （αc） decreased. Ag（Nb1-xa）O3 （x=0.4） ceramics sintered at 1 100℃ had the highest permittivity （516.8） and a lower tanδ （0.0021） at 1 MHz, and its temperature coefficient was about 191 ppm/℃. The sintering temperature of Ag（Nb1-xTa）O3 （x=0.4） was lowered by the addition of Bi2O3, and its dielectric properties were improved. Ag（Nb0.6Ta0.4）O3 ceramics with 2.5 wt% Bi203 addition presented the optimum dielectric properties （ε=566, tanδ= 0.0007 and αc≈0ppm/℃） （1 MHz）,     

Electrical and Magnetic Properties of Electron Doped BixCa1-xMnO3 （0〈x ≤0.33） Ceramics

Measurements of crystal structures, electrical and magnetic properties for the electron doped BixCa1-xMnO3 （0〈x≤〈0.33） reveal the presence of a variety of notable changes in correlation with magnetic transitions and charge ordering. Samples with x〈0.2 in general show a clear ferromagnetic transitions around 130 K. On the other hand, samples with 0.2≤x≤0.33 show much more complex low-temperature magnetic properties perhaps due to the coupling between the magnetic states and orbital/charge ordering. Structural transformations and structural modulations in the x=0.25 and 0.33 samples have been observed by transmission electron microscopy.     

La2O3掺杂对(Bi1/2Na1/2)0.94Ba0.06TiO3陶瓷性能与微结构的影响

采用传统陶瓷工艺方法制备了La2O3掺杂(Bi1/2Na1/2)0.94Ba0.06TiOa(BNBT6)无铅压电陶瓷,系统地研究了La2O3掺杂对该体系陶瓷介电、压电性能与微观结构的影响.结果表明:该体系具有很高的压电常数,是单一的钙钛矿结构,La2O3的添加对晶粒生长具有一定的抑制作用,线收缩率和相对密度增大.室温介电常数随着La2O3掺杂量的增加而增大.与不添加La2O3的陶瓷样品相比,添加少量La2O3可以使体系的弛豫特征更为明显.当掺杂量为0.1 wt%时,该体系陶瓷具有较好的综合性能:d3a=160 pC/N,kp=0.322.当掺杂量达到0.5 wt%以后,陶瓷的压电性能严重降低.     

Microstructure and Thermal Properties Analysis of （1-x）As2S3-x CdBr2 Glass System

The homogeneous glass sample for the ( 1 - x ) As2S3-xCdBr2, where x=0. 015,0. 035,0.05, was prepared by the conventional melt-quenched method. Amorphoas ( 1 - x ) As2S3-xCdBr2 alloys were determined by X-ray diffraction, thermal compreheasive analysis and Raman scattering. The glass transittion temperature (TR) deereases a bit with the addition of CdBr2 . Based on the experimental data, the microstrtucture is considered to be the discrete molecule species of AsBr3 and Cd - S atomic bonds or clusters are honigeneously dispersed in a disordered polymer network formed by AsS3 pyramids interlinked by sulfur bridges.