准同型相界附近PMN-PT陶瓷的介电与压电性能

采用铌铁矿预产物合成法制备了组成在相界附近的(1-x)Pb(Mg1/3Nb2/3)O3-x PbTiO3弛豫铁电陶瓷.陶瓷样品X射线衍射相组成和相结构分析表明:所有陶瓷样品均为纯钙钛矿相,没有检测出其它杂相;而且组成在x=0.33 mol处存在一准同型相界(MPB),在该相界附近三方相和四方相共存,而远离该相界则分别为纯三方相和四方相.在该相界附近组成具有优异的介电和压电性能:εm～38000,Ec～5 kV/cm,P～31.5 μC/cm2,d33～500 pC/N,这主要是由于宏观上的三方和四方两相共存,或微观上的微畴和宏畴共存引起的.     

Effects of Cr2O3 doping on the electrical properties and the temperature stabilities of PZT binary piezoelectric ceramics

The ceramics with Pb1.04Zr0.52Ti0.48O3 + z wt.% Cr2O3 were prepared using the traditional technique.The effects of Cr2O3 doping on the phase structure,the microstructure,and the electrical properties of ceramics were investigated.Meanwhile,the temperature stabilities of the resonant frequency (fr) were studied.The results showed that the △fr/fr,25℃ decreased with the addition of 0.2 wt.% - 0.8 wt.% Cr2O3 as compared with the undoped samples.The minimum value (-0.182%) of △fr/fr,25℃ was obtained for z = 0.6 wt.% Cr2O3 samples that sintered at 1260℃.The values of εT33/ε0 = 1650,tanδ = 0.006,d33 = 328 pC/N,Kp= 0.63,Qm = 2300 were obtained when Cr2O3 was 0.6 wt.%,which exhibited more excellent piezoelectric properties than other compositions such as those with z = 0.2 wt.%,0.4 wt.%,and 0.8 wt.%,but had a similar value as compared with the undoped samples.When the Cr2O3 additive increased,the Curie temperature moved toward low temperature and the changes of resonant frequency changed from positive to negative with increasing temperature.     

Influence of Sb<Subscript>2</Subscript>O<Subscript>3</Subscript> doping on the properties of KBT-NBT-BT lead-free piezoelectric ceramics

0.144(K0.5Bi0.5)TiO3-0.85(Na0.5Bi0.5)TiO3-0.006BaTiO3(KBT-NBT-BT) lead-free piezoelectric ceramics were prepared using a conventional solid state method.The influence of Sb2O3 doping on the crystal phase,surface microstructure and properties of the KBT-NBT-BT lead-free piezoelectric ceramics were investigated using X-ray diffraction(XRD),scanning electron microscope(SEM) and other analytical methods.The results show that all compositions are of pure perovskite structure solid states.Sb2O3 doping does not influence the microstructure of KBT-NBT-BT lead-free piezoelectric ceramics obviously in the Sb2O3 doping range of 0.1-0.5 wt.%.Sb2O3 functions as a donor when doped small amount,while functions as a acceptor when doped large amount.The piezoelectric strain constant(d33) increases first and then decreases;the dielectric constant(ε3T3/ε0) and the dielectric loss(tanδ) decrease continuously when the amount of Sb2O3 dopant increases.When the doping amount of Sb2O3 is 0.1 wt.%,the KBT-NBT-BT piezoelectric ceramics with good comprehensive properties are obtained,whose d33,ε3T3/ε0 and tanδ are 147 pC/N,1510 and 4.2%,respectively.     

Effects of Na/K ratio on the phase structure and electrical properties of Na<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>K<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>NbO<Subscript>3</Subscript> lead-free piezoelectric ceramics

Lead-free piezoelectric NaxK1-xNbO3(x = 0.3-0.8)(NKN) ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two dif...     

Effect of sintering temperature and composition on microstructure and properties of PMS-PZT ceramics

The piezoelectric ceramics xPb（Mn1/3Sb2/3）O3-（1-x）Pb（Zr1/2Ti1/2）O3 （abbreviated as PMS-PZT） were synthesized by traditional ceramics process. The effect of sintering temperature and the amount of Pb（Mn1/3Sb2/3）O3 （abbreviated as PMS） on phase structure, microstructure, piezoelectric and dielectric properties of PMS-PZT ceramics was investigated. The results show that the pure perovskite phase is in all ceramics specimens, the phase structure of PMS-PZT ceramics changes from tetragonal phase to single rhombohedral phase with the increasing amount of PMS. The dielectric constant εr, Curie temperature Tc, electromechanical coupling factor kp and piezoelectric constant d33 decrease, whereas the mechanical quality factor Qm and dielectric loss tanδ increase with the increasing amount of PMS in system. The optimum sintering temperature is 1 200-1 250 ℃. It is concluded that the PMS-PZT （x=0.07） ceramics sintered at 1 250 ℃ is suitable for high-power piezoelectric transformer. These properties include εr=674.8, tanδ =0.005 25, kp=0.658, Qm= 1 520, d33=230 pC/N, Tc=275 ℃.     

Effects of B2O3-SiO2 doping on electrical properties of Ba0. 65 Sr0. 35 TiO3 ceramics

Ba0. 65 Sr0. 35 TiOa ceramics doped with B2O3-SiO2 glass composition were prepared by using conventional solid-state reaction method. The effects of glass dopant on the dielectric and ferroelectric properties were investigated. The results show that the dielectric constant decreases while the dielectric loss increases after doping. And as the glass content increases the dielectric constant decreases while the dielectric loss changes slightly. From the complex impedance analysis the resistance and the relaxation time of the grain and the grain boundary can be calculated.Comparing the P--E hysteresis loop of undoped Ba0.65 Sr0.35 TiO3 ceramics with that of B2O3-SiO2 doped Ba0.65 Sr0.35 TiO3 ceramics, it can be seen that the remanent polarization decreases when the B2O3-SiO2 content is lower than 8% (molar fraction), and the coercive field increases with the increase of B2O3-SiO2 content.     

Sr掺杂对BaTiO3陶瓷结构与介电性能的影响

以BaCO3、SrCO3和TiO2为原料,通过固相烧结方法制备了Ba1-xSrxTiO3(0≤x≤1)。利用X射线衍射仪(XRD)、扫描电镜(SEM)、以及阻抗分析仪分别分析Ba1-xSrxTiO3相结构、显微组织和测量介温谱。结果表明,Sr的掺杂没有改变BaTiO3的晶体结构,Ba1-xSrxTiO3(0≤x≤1)固溶体为完全互溶固溶体,为单一的立方相,但随着锶含量的增加,居里点逐渐降低。     

表面掺杂CeO2对2Y—TZP陶瓷抗低温水热腐蚀的影响

比较了对２Ｙ－ＴＺＰ陶瓷采用表面掺杂ＣｅＯ２和体掺杂ＣｅＯ２两种不同方式处理后，２Ｙ－ＴＺＰ陶瓷低温水热腐蚀前后的抗弯强度的变化，结果表明，对Ｙ－ＴＺＰ陶瓷进行表面掺杂ＣｅＯ２，不仅可以克服体掺杂ＣｅＯ２时抗弯强度大幅度下降问题，而且可以明显改善低温水热腐蚀对Ｙ－ＴＺＰ陶瓷力学性能的影响，表面掺杂ＣｅＯ２对２Ｙ－ＴＺＰ陶瓷抗低温水热腐蚀的原因，是既保持了Ｙ－ＴＺＰ陶瓷整体对等温相变的约束，又阻止了     

Effect of Cr doping on structure of LiMnO_2

1　INTRODUCTIONThelayeredLiCoO2 compoundhasbeensuccess fullycommercializedbecauseofitshighenergydensi tyanditsexcellentstabilitywithrespecttoextendedelectrochemicalcycling .However,fromtheeconomicandenvironmentalpointofview ,cheaper ,lessertox icandsaferintercalationmaterialsthanLiCoO2 com poundarerequired .LiMnO2 compoundsareofinterestasintercalationcathodesforrechargeableLibatteriesduetotheirhightheoreticalcapacity (2 85mAh/g) ,lowcostandnontoxicity .OrthorhombicLiMnO2 (o LiMnO2 ,…     

铋基无铅压电陶瓷Bi0.5(Na0.82K0.18)0.5TiO3-BiCrO3的微观组织与电性能

采用传统陶瓷制备方法,制备一种新型无铅压电陶瓷 (1-x)Bi0.5(Na0.82K0.18)0.5TiO3-xBiCrO3 (BNKT-BCx).研究Bi基铁电体BiCrO3对BNKT-BCx陶瓷晶体结构和压电介电性能的影响.结果表明:在所研究的组成范围内,陶瓷材料的主体结构为纯钙钛矿固溶体,微量BiCrO3(x=0～0.02,摩尔分数)不改变陶瓷的晶体结构;当BiCrO3含量x＞0.02时,晶体结构由三方、四方共存转变为伪立方结构,并出现明显的第二相;当x=0.015时,d33=168 pC/N;当x=0.01时,kp=0.32,为该体系压电性能的最大值;随BiCrO3含量的增加,陶瓷的低温介电反常峰向低温移动,高温介电反常峰向高温移动,反铁电相区域增加,弥散指数增加.     

Piezoelectric and dielectric properties of Lix（K0.46Na0.54） 1-xNb0.86Ta0.1 Sb0.04O3 lead-free ceramics

Lead-free piezoelectric ceramics Lix（K0.46Na0.54）1-xNb0.86Ta0.1Sb0.0403 （with x ranging from 0 to 0.1） were synthesized by conventional solid state sintering method. The effect of cationic substitution of Li for K and Na in the A sites of perovskite lattice on the structure, phase transition behavior and electrical properties were investigated. Morphotropic phase boundaries（MPB） between orthorhombic and tetragonal phase are found in the composition range of 0.06≤x≤0.08. Analogous to Pb（Zr, Ti）O3, the dielectric and piezoelectric properties are enhanced for the composition near the morphotropic phase boundary. The Li0.06（K0.46Na0.54）0.94- Nb0.86Ta0.1Sb0.04O3 ceramics show excellent electrical properties, that is, piezoelectric constant d33=215 pC/N, planar electromechanical coupling factor kp=41%, dielectric constant ε33^T /ε0=1 303, and dielectric loss tan δ=2.45%. The results indicate that Lix（K0.46Na0.54）1 -xNb0.86Ta0.1Sb0.0403 ceramic is a promising lead-free piezoelectric material.     

Al掺杂对Ti_3SiC_2陶瓷制备和性能的影响

采用热压烧结法制备了Al掺杂的Ti_3SiC_2陶瓷,通过X射线衍射仪、扫描电子显微镜、能谱仪、矢量网络分析仪等,分别对所制备的样品进行了表征和抗氧化性能、微波介电性能测试。结果表明:所制备的Al掺杂陶瓷具有相当高的Ti_3SiC_2质量分数,陶瓷晶粒呈现明显的层状特征。相比于未掺杂样品,通过Al掺杂途径,可显著提高Ti_3SiC_2陶瓷1200℃高温下的抗氧化性能,并使Ti_3SiC_2陶瓷的介电常数实部ε'和虚部ε"值大幅度增加,其在8.2~12.4 GHz频率范围的均值分别为60.8和6.28。     

Bi掺杂对Ba_(6-3x)La_(8+2x)(Ti_(0.95)Zr_(0.05))_(18)O_(54)(x=2/3)陶瓷的烧结性能和介电性能的影响

采用传统固相反应法制备Ba6-3x(La1-mBim)8+2x(Ti0.95Zr0.05)18O54(x=2/3)微波介质陶瓷,研究Bi掺杂对Ba6-3xLa8+2x(Ti0.95Zr0.05)18O54(x=2/3)陶瓷的烧结性能、微观结构以及介电性能的影响。结果表明:当0m0.4时,Bi3+取代A1位的La3+生成单相类钨青铜型固溶体;当Bi3+的掺杂量超过这个范围时,La0.176Bi0.824O1.5作为第二相出现在固溶体中;Bi3+的掺入使Ba6-3xLa8+2x(Ti0.95Zr0.05)18O54(x=2/3)陶瓷的烧结温度从1400℃降低到1300℃,同时,其介电常数大幅度提高,谐振频率温度系数减小,但品质因数急剧减小;当m=0.05时,1350℃下保温2h烧结获得的陶瓷具有微波介电性能,εr=88.63,Q·f=4395GHz,τf=6.25×10-6/℃。     

Microstructure and electrical properties of Ti-modified (Na_(0.5)K_(0.5))(Ti_xNb_(1-x))O_3 lead-free piezoelectric ceramics

Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the lead-free NKNT ceramics were investigated. X-ray diffraction re-sults indicated that Ti4+ had diffused into the (Na0.5K0.5)NbO3 lattices to form a solid solution with a perovskite structure. The introducing of Ti into the (Na0.5K0.5)NbO3 solid solution effectively reduced the sintering temperature and...     

Piezoelectric and dielectric properties of Cr-doped PSN-PZN-PZT quaternary piezoelectric ceramics

PSN-PZN-PZT x wt.%Cr2O3, x=0.0-0.9, were prepared by conventional mixed oxide techniques at sintering temperatures of 1220℃-1300℃ for 2 h. The effect of sintering temperature on the microstructure and the piezoelectric properties was investigated by XRD, SEM, and other conventional measurement. The result indicated that with temperature increasing, the valence of Cr ion from Cr^5 or Cr^6 changes into Cr^3 , and the piezoelectric properties turn hard. With increasing Cr2O3 content, the amount of rhombohedral phases increases and the morphotropic boundary phase is correspondingly shifts to rhombohedral phase. A uniform microstructure and excellent comprehensive properties were obtained at 1240℃ as the amount of Cr2O3 is 0.5 wt.%.     

CaO掺杂对10NiO-NiFe2O4复合陶瓷烧结致密化的影响

采用冷压烧结技术制备了CaO掺杂的10NiO-NiFe2O4复合陶瓷,研究了CaO掺杂量及烧结温度对10NiO-NiFe2O4复合陶瓷物相组成、显微结构及致密度的影响。结果表明:当CaO掺杂量为0~4%(质量分数)时,烧结样品中主要含有NiO和NiFe2O4两种,CaO与10NiO-NiFe2O4陶瓷组分反应并形成低熔点相,且Ca2 离子固溶到基体组分中,促进致密化烧结,降低了烧结温度;当CaO掺杂量为4%时,过剩的CaO存在于陶瓷颗粒间,抑制了致密化过程的进行;于1 200℃烧结时,2?O掺杂样品的相对密度最大,达到98.75%,比未掺杂样品的相对密度提高近24%;当烧结温度从1 200当升高到1 400℃时,CaO掺杂量为0、0.5%和1.0%的样品相对密度提高20%以上,但当CaO掺杂量为2%和4%时,陶瓷样品相对密度反而下降,且晶粒明显长大。     

PMN-PZN-PT铁电陶瓷的准同型相界及电学性能

基于准同型相界(morphotropic phase boundary, MPB) 线性组合规律,研究Pb(Mg_(1/3)Nb_(2/3))O_3 -Pb(Zn_(1/3)Nb_(2/3))O_3-PbTiO_3 (PMN-PZN-PT)三元系的MPB区域,并探求电学性能优越的组分.实验选取(1-x) (0.67 PMN- 0.33 PT)-x(0.91 PZN-0.09 PT) 系列中x=0～0.85的8个实验点;为减少焦绿石相的生成,陶瓷试样用铌铁矿预产物法合成,最终在1120～1160 ℃烧成.X射线衍射分析表明该系列试样均为钙钛矿结构,且处于四方与菱方两相共存态,验证了两个子二元系MPB组分的连线均为该三元系的MPB区域.少量的PZN-PT取代PMN-PT可以提高该三元系的电学性能;在x=0.1的组分获得该系列的最优性能:极值介电常数ε_(m,1 kHz)=28 030,剩余极化强度Pr=32.5 μC/cm~2,压电系数d_(33)=545 pC/N.     

Study on magnetic and dielectric properties of YMnO3 ceramics

The magnetic and dielectric properties were investigated in the hexagonal YMnO₃ ceramics synthesized by sol-gel method. An antiferromagnetic order about 70 K and a weak ferromagnetic order at 5 K have been detected in YMnO₃ ceramics. In addition, we observed also the exchange-bias (EB) effect at low temperatures and it may originate from exchange coupling at the interface between ferromagnetic and antiferromagnetic orders for the co-existence of these two orders in some temperature region in hexagonal YMnO₃. Furthermore, the dielectric measurements showed two thermally activated relaxation behaviors following the Arrhenius law in 290-430 K and above 500 K in YMnO₃ ceramics and they can be explained as the dipolar effects associated with the charge carrier hopping between Mn²⁺ and Mn³⁺ and oxygen vacancy, respectively.