Sb掺杂K0.5Na0.5NbO3无铅压电陶瓷相结构和电学性能的研究

采用传统固相烧结法,在1060 ℃制备(K0.5Na0.5)Nb1-xSbxO3(KNNS,x=0、0.01、0.02、0.03和0.04)无铅压电陶瓷,研究了Sb掺杂对KNN陶瓷物相结构、微观形貌和电学性能的影响.研究结果表明:Sb可以取代钙钛矿结构中B位的Nb位置,Sb取代Nb的最大量为0.03≤x≤0.04,当x=0.04时产生杂相;通过XRD图谱分析表明,x=0时陶瓷为单一的正交相结构,0.02≤x≤0.03时为正交-四方相共存,x=0.04时转变为三方相结构.Sb的掺杂具有细化晶粒的作用,随着Sb含量的增加,晶粒平均尺寸减小,晶粒大小变得均匀,介电性能增强.     

CeO_2掺杂KNN-LiNbO_3无铅压电陶瓷的压电与介电性能研究

采用传统固相烧结法制备了0. 98K_(0. 5)Na_(0. 5)NbO_3-0. 02 Li NbO_3-x CeO_2(0.98KNN-0.02LN+x CeO_2)无铅压电陶瓷。研究了不同CeO_2掺杂含量(x=0、0.01、0.02、0.03、0.04)对0.98KNN-0.02LN陶瓷显微结构和电学性能的影响。研究结果表明:当CeO_2掺杂含量从x=0.00到x=0.01和从x=0.02到x=0.03时,样品出现了正交-四方相转变。当x=0.00和x=0.02时,样品都处于正交与四方两相共存状态。CeO_2少量掺杂时Ce4+完全进入晶格,表现为"受主"掺杂的特性;而大量CeO_2掺杂时,有杂相的生成,主要起到烧结助剂的作用。样品在1080℃下烧结,当掺杂含量为x=0.02时取得最佳的综合性能:d33=104 p C/N,Qm=2201,kp=0.24423,εr=804.2,tanδ=8.748%。     

CuO掺杂对Ba_(0.96)(Bi_(0.5)K_(0.5))_(0.04)TiO_3陶瓷烧结行为和介电性能的影响

采用固相法制备了Ba0.96(Bi0.5K0.5)0.04TiO3-xCuO(x=0~0.05)陶瓷,通过XRD、SEM和阻抗分析仪等测试手段研究了CuO掺杂对Ba0.96(Bi0.5K0.5)0.04TiO3陶瓷烧结温度、相组成、显微结构和介电性能的影响。结果表明:在x=0~0.05掺杂浓度范围内,所有陶瓷样品均为钙钛矿结构,且没有第二相的生成。当x≤0.03时,CuO与Ba0.96(Bi0.5K0.5)0.04TiO3形成固溶体,Cu2+进入晶格取代Ti4+的位置。在x=0.02时,陶瓷样品的四方率c/a达到最大,居里温度TC最高为148.5℃。当x≥0.04时,过量的CuO在晶界处形成液相,显著降低烧结温度。当x=0.05时,烧结温度降为1275℃,由于液相的产生,陶瓷样品致密度提高,内部缺陷减少,介电损耗最小。在掺杂CuO的陶瓷样品中,介电常数先增大后减小,在x=0.01时达到最大。     

Y_2O_3掺杂对(Ba_(0.85)Ca_(0.15))Zr_(0.1)Ti_(0.896)Sm_(0.004)O_3无铅压电陶瓷介电弛豫与电性能的影响

采用固相法制备了(Ba0.85Ca0.15)1-xYxZr0.1Ti0.896Sm0.004O3(BCZTS-Yx)无铅压电陶瓷.研究了Y2O3含量对BCZTS-Yx无铅压电陶瓷相结构、压电与介电性能的影响.结果表明:Y3+作为施主掺杂物占据A位。当0.004≤x≤0.006时,陶瓷存在三方相与四方相共存的准同型相界结构。当x=0.006时,陶瓷具有最佳的电性能,分别为d33=384 pC/N,kp=37.2%,εr~6775,tanδ~2.04%.利用Curie-Weiss定律对该实验结果进行拟合,发现x为0.006的样品的介电弛豫特征更为明显。     

Pb_(0.92)Sr_(0.08-x)Ba_x(Sb_(2/3)Mn_(1/3))_(0.05)Zr_(0.48)Ti_(0.47)O_3的制备与性能研究

采用传统固相烧结法制备了Pb_(0.92)Sr_(0.08-x)Ba_x(Sb_(2/3)Mn_(1/3))_(0.05)Zr_(0.48)Ti_(0.47)O_3(PSBSM-PZT)压电陶瓷样品。研究了不同Sr2+、Ba2+掺杂含量对样品的相结构、微观形貌、压电和介电性能的影响。结果显示:所有样品均为钙钛矿结构。而当x=0.02~0.06时,陶瓷样品组分位于准同型相界区(MPB)。由于位于准同型相界区域的陶瓷样品对于电畴的转向具有促进作用,所以处于MPB区域的陶瓷样品具有较大的压电和介电性能,但同时由于电畴转向带来的较大内摩擦和结构损耗,从而提高了材料的机械损耗和介电损耗。当x=0.02时的陶瓷样品获得最佳的综合性能:d33=346 pC/N,kp=0.58,Qm=1217,εr=1724,tanδ=0.774%。     

Na/Bi配比对0.94(Bi_(0.5+x)Na_(0.5-x))TiO_3-0.06BaTiO_3压电陶瓷组织结构与性能的影响

采用传统固相烧结方法制备出0.94(Bi_(0.5+x)Na_(0.5-x))TiO_3-0.06BaTiO_3(BNBT6)二元系无铅压电陶瓷(x分别为0,0.08%,0.12%,0.16%,0.24%和0.50%摩尔分数),系统地研究了不同Na/Bi配比对BNT基陶瓷材料物相结构、显微组织和压电、介电性能的影响。结果表明:添加不同的Na/Bi,所制备的BNBT6压电陶瓷组织分布均匀、致密度高,存在三方-四方共存的准同型相界结构,且不同的Na/Bi配比不影响陶瓷的相结构,但其烧结性能及电性能与Na/Bi配比密切相关,当x=0.16%时,BNBT6陶瓷样品的性能最佳,相对密度达到97%,在1 kHz的测试频率下,BNBT6陶瓷样品的压电常数d_(33)为138 PC/N、介电常数ε_r为1486、介电损耗tanδ为2.1%、机械品质因数Q_m为217。     

模板晶粒定向生长技术制备(Na_(0.8)K_(0.2))_(0.5)Bi_(0.5)TiO_3无铅压电陶瓷的性能研究

以熔盐法和质子取代法制备的片状Nb2O5粉体为模板晶粒,固相法合成的(Na0.8K0.2)0.5Bi0.5TiO3(NKBT)粉体为基料,分别采用固相压制成型(干法)和流延成型(湿法)工艺制备出具有较高取向度的织构化NKBT无铅压电陶瓷,研究了两种成型工艺对NKBT无铅压电陶瓷的显微结构、压电性能和介电性能的影响。结果表明:采用湿法工艺制备的织构陶瓷的各项性能优于干法工艺,采用湿法工艺在1150℃保温5 h时,可以获得较高织构度(f=0.66)的NKBT无铅压电陶瓷,并具有优异的压电和介电性能:压电常数d33=149 pC/N,介电常数εT33/ε0=912和平面机电耦合系数kp=29.4%。     

SnO_2掺杂对(Ba_(0.85)Ca_(0.15))(Ti_(0.9)Zr_(0.1-x)Sn_x)O_3无铅压电陶瓷介电弛豫与电性能的影响

采用固相烧结法制备了(Ba_(0.85)Ca_(0.15))(Ti_(0.9)Zr_(0.1-x)Sn_x)O_3(BCZTS)无铅压电陶瓷。研究了不同含量SnO_2(x=0,0.02,0.04,0.06,0.08)对BCZT无铅压电陶瓷相结构、压电性能、介电性能和铁电性能的影响,并利用XRD、SEM、准静态d33测试仪等表征样品。结果表明,所有样品均为单一钙钛矿结构。当掺杂x=0.02时,(Ba_(0.85)Ca_(0.15))(Ti_(0.9)Zr_(0.1-x)Sn_x)O_3无铅压电陶瓷材料的综合性能优异:d33=553 p C/N,kp=49%,εr~7474(1 k Hz),tanδ~1.5%(1k Hz),Pr=6.06μC/cm~2,Ec=2 k V/cm,利用Curie-Weiss定律对该实验结果进行拟合,发现x=0.02的样品的介电弛豫特征更为明显。     

Bi(Zn_(0.5)Ti_(0.5))O_3对Bi_(0.5)Na_(0.5)TiO_3基陶瓷相结构及弛豫性的影响

采用固相反应合成法制备了(1-x)(0.96 Bi0.5Na0.5TiO3-0.04 BaTiO3)-xBi(Zn0.5Ti0.5)O3陶瓷(x≤0.10)。通过X射线衍射,介电温度谱等对该体系陶瓷的相结构及弛豫特性进行了研究。结果发现,该陶瓷在Bi(Zn0.5Ti0.5)O3加入量低于0.05时呈现纯钙钛矿结构。此外,随着Bi(Zn0.5Ti0.5)O3加入量的增加,其相结构由三方-四方共存向赝立方结构转变;同时,陶瓷的弥散因子上升,偶极子取向冻结活化能下降,表明BZT的加入明显地增加了0.96Bi0.5Na0.5TiO3-0.04 BaTiO3陶瓷的弛豫性。     

Nb_2O_5掺杂对Pb(Mg_(1/3)Nb_(2/3))O_3-PbZrO_3-PbTiO_3陶瓷组织与性能的影响

采用固相烧结法制备Nb2O5掺杂的Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3+0.5mol%ZnO(PMN-PZT)压电陶瓷,研究了不同Nb2O5掺杂量对材料结构及压电介电性能的影响。实验结果表明,随着Nb2O5掺杂量的增加(0~1mol%),PMN-PZT陶瓷的晶界强度提高,断裂模式由沿晶断裂逐渐转变为穿晶断裂,而且陶瓷的压电介电性能升高。当Nb2O5掺杂量为1mol%时,1250℃烧结的陶瓷样品性能参数为:d33=430 pC/N,Qm=60,kp=0.52,kt=0.38,εr=3620,tanδ=0.017。     

Direct preparation of K0.5Na0.5NbO3 powders

K_0.5Na_0.5NbO₃ powders have been directly synthesized by an alternative solid–state method. Stoichimometric mixture of ammonium niobium oxalate and C₄H₄O₆KNa·4H₂O were calcined in temperature range from 500 to 800 °C for 3 h. The precursor and calcination products were characterized with respect to stoichiometry, purity, crystalline structure, particle size and powder morphology using X–ray diffraction (XRD), X‐ray fluorescence (XRF) spectrometer, scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectra, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and UV–Vis diffuse reflectance (UV–Vis) spectroscopy. XRD and XRF results reveal that stoichiometric K_0.5Na_0.5NbO₃ powders could be synthesized by the method. The particle size is about 68 nm for the precursor calcined at 500 °C according to XRD data, which is in good agreement with SEM data. The average band gap energy is estimated to be 3.18 eV by UV–vis diffuse reflectance spectra. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

(Na_(0.5)Bi_(0.5))TiO_3-(K_(0.5)Bi_(0.5))TiO_3无铅铁电单晶的生长、结构与介电特性

采用高温自助熔剂法制备了(Na0.5Bi0.5)TiO3-(K0.5Bi0.5)TiO3(简称:NBT-KBT)无铅铁电单晶,晶体尺寸为5mm×6mm×1mm。利用X射线衍射(XRD)手段研究了NBT-KBT单晶的相结构,结果表明晶体样品为钙钛矿四方相结构。Raman散射结果也表明了NBT-KBT单晶的拉曼振动模式具有四方相结构特征。利用扫描电镜(SEM)和透射电镜(TEM)研究了单晶的表面形貌和微结构特征。另外,单晶介电常数随温度以及频率的变化关系显示单晶具有弛豫铁电体特性。     

La∶BiFeO3/Bi0.5(Na0.85K0.15)0.5TiO3纳米复合薄膜的铁电特性

采用脉冲激光沉积技术(pulsed laser deposition,PLD),在Pt/Ti/SiO2/Si基片上制备了La0.1Bi0.9FeO3(BFO),Bi0.5(Na0.85K0.15)0.5TiO3(BNKT)和BFO/BNKT纳米复合薄膜.结果表明,复合薄膜的铁电特性比单层的BFO、BNKT薄膜有所增强.利用压电力显微镜(piezoresponse force microscopy,PFM)观察到了铁电畴.由于畴结构内部矫顽力分布不均匀,导致极化反转随时间改变,疲劳测试结果也证实了该结论.随着转换周期的增加,极化随之增强.运用PFM测量了纳米级的压电响应,同样证实了BFO/BNKT复合薄膜中的畴反转现象.     

织构化K0.5Na0.5NbO3无铅压电陶瓷的性能研究

以分析纯Na2CO3、Bi2O3和Nb2O5为原料,以NaCl为熔盐,采用二次熔盐法和拓扑化学反应法合成各向异性片状NaNbO3粉体.以该片状NaNbO3粉体为模板品粒,以固相法合成的NaNbO3和KNbO3粉体为基料,采用流延工艺制备出较高取向度的织构化K0.5Na0.5NbO3(KNN)无铅压电陶瓷,系统研究了模板含量、烧结温度和保温时间等工艺参数对织构化KNN陶瓷显微结构和压电性能的影响规律.研究结果表明:随着模板含量的增加,陶瓷的取向度逐渐增加,当模板含量为15 wt%时,陶瓷的取向度可达0.69,当模板含量为10 wt%,1100 ℃下保温5 h烧结,可以获得具有一定织构度(f=0.58)的KNN陶瓷,并表现出优异的压电性能,d33=128 pC/ N.     

Crystal structure,dielectric properties of (K0.5Na0.5)NbO3 single crystal grown by flux method using B2O3 flux

Lead free piezoelectric single crystals of sodium potassium niobate (K_0.5Na_0.5)NbO₃ (KNN) were grown by high‐temperature solution method using two different fluxes; one with a mixture of NaF and KF and other with addition of B₂O₃ along with the mixture. In the present study, the growth of KNN crystals without B₂O₃ flux and the same with B₂O₃ flux were compared. It was found that additions of small amounts of B₂O₃ lowered the melting temperature of the solid solution and enabled better dielectric properties. Phase analysis showed that all samples were crystallized in pure orthorhombic perovskite phase. AFM morphological studies showed that the addition of B₂O₃ flux increased the roughness of the grown crystal. Further, addition of B₂O₃ flux slightly decreased the orthorhombic to tetragonal phase transition temperature T_(O—T) and the Curie temperature T_C. The ferroelectric behaviour of KNN single crystal has been investigated at room temperature. The crystal grown using B₂O₃ flux exhibited a remanent polarization (P_r) ∼ 32 μC/cm² and coercive field (Ec) of ∼11.8 kV/cm whereas the crystal grown without the use of B₂O₃ flux had a remanent polarization (P_r) ∼ 36 μC/cm² and coercive field (Ec) of ∼14.6 kV/cm.     

Bi_(0.5)(Na_(0.82)K_(0.18))_(0.5)TiO_3-BiFeO_3无铅压电陶瓷的介电特性

采用固相反应法制备了系列(1-x)Bi0.5(Na0.82K0.18)0.5TiO3-xBiFeO3(BNKT-BFx)陶瓷.研究了该陶瓷在室温至500 ℃范围内的介电性能.结果表明:该陶瓷的介电温谱与典型弛豫铁电体的特征不同,存在两个介电反常峰和一个介电损耗峰,只在低温介电反常峰温度附近具有明显的介电常数的频率依赖性,居里温度随频率增加基本不变.首次提出了弛豫铁电体分为本征弛豫和非本征弛豫铁电体的理论.通过分析极化前和极化后陶瓷的介电温谱,发现该体系低温介电反常峰温度附近的介电频率依赖性为空间电荷和缺陷偶极子极化引起的非本征弛豫.     

Na3La2(BO3)3的晶体结构

以Na2 CO3 H3 BO3 NaF为助熔剂 ,使用顶部籽晶法生长出Na3 La2 (BO3 ) 3 透明单晶。测定了Na3 La2 (BO3 ) 3 的晶体结构 ,该晶体属正交晶系 ,空间群 :Amm2 (No .38) ,晶胞参数为a =0 .5 15 80 (10 )nm ,b =1.135 0 (2 )nm ,c =0 .732 30(15 )nm ,α=β=γ =90° ,V =0 .4 2 871(15 )nm3 ,密度 :4 .0 5 3g/cm3 。晶体结构中的硼氧基团是平面的BO3 基团 ,BO3 基团相互独立 ,且与Na(1)O6、Na(2 )O8、Na(3)O6和La(1)O9配位多面体连结形成三维网络骨架结构。讨论了Na3 La2(BO3 ) 3 的晶体结构与倍频效应的关系。     

The 0.96(Bi0.5Na0.5)TiO3 – 0.04BaTiO3 crystal structure: A high‐Q,high‐counting statistics synchrotron diffraction analysis

A synchrotron powder diffraction experiment, especially designed to shed light on the controversial problem of the crystal structure of 0.96(Bi_0.5Na_0.5)TiO₃ – 0.04BaTiO₃, is reported. The investigated material is a key component of the current international search for lead‐free ferro‐piezoelectrics. A wide angular range diffraction pattern was measured in high resolution configuration, with emphasis on trustable counting stastistics in the high‐Q interval. Cc and R3c structural models were tried as primary phases. The obtained experimental results are incompatible with the monoclinic model and clearly favor the rhombohedral symmetry.