Synthesis and Piezoelectric Properties of Lead-free （ Bi0.5 Na0.5 ）1-x（BaaSrb）xTiO3 Ceramics

A new group of lead-free piezoelectric ceramics,（Bi0.5 Na0.5）1-x（BaaSrb）xTiO3（abbreviated as BNBST[100x-100a/100b],0〈x〈1,a＋b=1）,was synthesized.The ceramics were prepared by conventional ceramic sintering technique,and the ceramics with density of 95% of the theoretical one can be sintered without the atmosphere control during the sintering process.The results of the X-ray diffraction（XRD） data show that the ceramics possess a single perovskite phase.The measurements of dielectric and piezoelectric properties reveal that the ceramics provide relatively high piezoelectric charge constant d33 and high planar electromechanical coupling factor kp.For the BNBST6-95/5 ceramics,d33 is equal to 170pC/N,and kp is equal to 32.0%.The fabrication technique for these ceramics is conventional and stable.     

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.     

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.     

Dielectric and Magnetic Properties of (1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 Composite Ceramics

(1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4(0 x 1.0) composite ceramics were synthesized by a conventional solid state reaction method.The phase formation,microstructure,and dielectric and magnetic properties were investigated by X-ray diffraction,scanning electron microscopy,precision impedance analysis,and vibrating sample magnetometry,respectively.The results indicate that the composite ceramics are composed of both perovskite phase Ca TiO_3 and spinel phase Ni_(0.5)Zn_(0.5)Fe_2O_4.The maximal relative density for 0.5CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 composite ceramics reaches 97.8%,as it has been sintered at the temperature of 1260 ℃ for 3 h.Dielectric constant and loss tangent of(1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 composite ceramics show dispersion in the low frequency range.Their phase transition temperature of the dielectric constant shifts to lower temperatures with the increase of Ni_(0.5)Zn_(0.5)Fe_2O_4 content.This phenomenon is attributed to that the phase transition temperature of CaTiO_3 is higher than that of Ni_(0.5)Zn_(0.5)Fe_2O_4.The saturation magnetization of (1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 composite ceramics increases with the Ni_(0.5)Zn_(0.5)Fe_2O_4 ferrite content.     

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.     

Effect of Sintering Time on Structure and Properties in CuO-doping KNN-LS-BF Piezoelectric Ceramics

The 0.6 mol% CuO-doping 0.996(0.95 Na_(0.5)K_(0.5)NbO_3-0.05 LiSbO_3)-0.004 FeBiO_3(KNN-LSBF-CuO) piezoelectric ceramics were synthesized by a solid-state reaction technique, and the structure and piezoelectric properties dependence of sintering time in KNN-LS-BF-CuO ceramics were studied. It is found that all the samples sintered for various time are perovskite structure mixed with orthorhombic symmetry phase and tetragonal phase, but the sintering time has significant influences on the crystalline and properties. When the sintering time increases from 2 hours to 6 hours, the grain of KNN-LS-BF-CuO ceramics becomes more homogeneous and more tight-arrangement. The experimental results reveal that the longer sintering time than 4 hours is beneficial for improving partial properties, such as d_(33), tgδ, and Q_m, but is adverse to ε_r and k_p, the KNNLS-BF-CuO ceramics with optimum properties can be synthesized for 6 hours at 1 060 ℃.     

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.     

Microstructures and Electrical Properties of Bi_(0.5)-(Na_(1-x-y)K_xLi_y)_(0.5)TiO_3 Lead-free Piezoelectric Ceramics

The microstructures and electrical properties of Bi0.5(Na1-x-yKxLiy)0.5TiO3 lead-free piezoelectric ceramics were studied.These ceramics were prepared by conventional ceramic technique.XRD analysis reveals that the ceramics possess almost pure perovskite phase when y≤0.2.The SEM results show that,with more amounts of Li+,the crystalline grain growing speed is accelerated,and the sintering temperature can effectively be decreased.The measurements of piezoelectric properties indicate that the ceramics with relatively low amount of Li+ and high amount of K+ have comparatively large piezoelectricity.The dielectric measurements show that the ceramics have properties like relaxor ferroelectrics and diffuse phase transition(DPT) at Td and Tc,respectively.The results of ferroelectric measurements reveal the system has relatively higher remanent polarization Pr(27.6 μC/cm2) and lower coercive field Ec(37.5 kV/cm).     

Effect of Lead Contents on the Properties of PMSZT Piezoelectric Ceramics

The effects of Pb content on crystallographic phase, microstructure, electric-properties of PMSZT piezoelectric ceramics were studied. The crystallographic phase and microstructure of the ceramics were examined by using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The experimental result shows that the samples consist of a mixture of tetragonal and rhombohedral phases in the range of lead contents x=0.95-1.06, grains grow up homogeneously and the minimum value of Curie temperature was obtained with x-=1.02. With Pb content x〈l.02 or x〉1.02, the Curie temperature moves towards a high temperature. A well-situated electric-properties of ET33/E0 （1660）, d33 （344pC/N）, Kp （0.684）, Qm （2350）,tan 3（0.0030） were obtained when lead content x=1.02.     

The microstructure and properties of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramic system

The microstructure and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3(x=0,0.04,0.08,0.12,0.16) ceramic system were investigated.The Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics were prepared by the traditional solid-state reaction method and were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and Raman spectrometer.The sintering ability and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 were found to be improved with the doping of Mn4+ and W6+ ions.The densification temperature of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics decreased from 1 080 ℃ to 1 000 ℃ when x increased from 0 to 0.16.Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramic was found to have the best dielectric properties when x=0.08,larger permittivity(■=547) and smaller dielectric loss(tan■=0.00156).     

(Na_(0.5)K_(0.5))NbO_3基无铅压电陶瓷压电常数的研究

针对目前无铅压电陶瓷的压电常数d33偏小的情况,采用传统的烧结方法制备了(Na0.5K0.5)NbO3基无铅压电陶瓷(Na0.5K0.45Li0.05)Nb0.95-xSbxTa0.05O3(x=0.03,0.06,0.09,0.12),研究了在Li和Ta含量固定的情况下,Sb元素的添加量和烧结温度对陶瓷的压电常数的影响.研究结果表明,适量Sb元素的掺杂可以大幅度提高陶瓷的压电常数d33,陶瓷样品的压电常数d33随着Sb含量的增加先增大后减小.烧结温度可以影响陶瓷的密度,进而影响其压电常数.在1130℃的最佳烧结温度下,Sb含量x=0.09时,陶瓷样品表现出最佳的压电性能,压电常数d33=328 pC/N.     

Struchre and Electrical Properties of (Na0.5Bi0.5)0.94Ba0.06TiO3 Ceramic with 0.5 wt% 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(Ec)and mechanical quality factor(Qm)together with a decrease of dielectric constant(?r)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(Pr)and coercive field.     

Na_(0.5)K_(0.5)NbO_3织构化陶瓷制备与表征

采用凝固法制备出各向异性的片状钛酸钡作为模板,利用模板晶粒生长(TGG)法制备出Na0.5K0.5NbO3(NKN)织构化陶瓷.研究了NKN织构化陶瓷的工艺、组织和性能.研究结果表明,钛酸钡可以作为NKN陶瓷的模板,在陶瓷烧结过程中诱导NKN晶粒的生长,模板的取向决定了NKN陶瓷晶粒取向,随着烧结温度的升高陶瓷的压电性能(d33)达到69 pC/N,在合理的烧结工艺下得到了取向比较明显的织构化陶瓷.     

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…     

Effect of doped Mn on piezoelectric properties of (Na_(0.5)Bi_(0.5))_ (0.92)Ba_(0.08)TiO_3 lead-free ceramics

1INTRODUCTION Therehasbeengreatinterestinthestudiesof thelead freematerialswithdielectric,piezoelectricandferroelectricpropertiesinthefieldoffunction almaterialsfortheiramiabilitytoenvironment. (Na1/2)TiO3(NBT)ceramicshavebeenwidelystudiedbecauseoftheirrelativelylargeremnant polarization(Pr)of38μC/cm2andcoercivefieldof 73kV/cm[1].However,NBTcannotreplacelead zirconatetitanate(PZT)basedceramicsbecausethepiezoelectricpropertiesofNBTarestillnot comparabletothoseofPZT[24].Recently,m…     

二次烧结对KNN-LS-Bi(Mg0.5Ti0.5)O3无铅压电陶瓷性能的影响

采用传统固相烧结法和二次烧结工艺制备了xBi(Mg0.5Ti0.5)O3-0.95K0.5Na0.5NbO3-0.05LiSbO3(xBMT-KNN-LS)无铅压电陶瓷,研究了二次烧结工艺对xBMT-KNN-LS陶瓷性能的影响。结果表明:采用传统的陶瓷烧结工艺所得到的性能为压电常数d33=220 pC/N、平面机电耦合系数kp=39.6%、介电损耗tanδ=6.38%。而采用二次陶瓷烧结工艺得到的最佳性能为d33=254 pC/N、kp=37.8%、tanδ=4.81%,因此,二次烧结对该体系的压电性能有显著的影响。     

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.     

（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。