Dielectric properties and phase transitions of La_2O_3- and Sb_2O_3-doped barium strontium titanate ceramics

The dielectric properties and phase transition characteristics of La2O3- and Sb2O3-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray diffraction method and scanning electron microscope was also employed to observe the surface morphologies. It is found that （La,Sb）-codoped barium strontium titanate ceramics exhibit typical perovskite structure and the average grain size decreases dramatically with increasing the content of Sb2O3. Both La3＋ ions and Sb3＋ ions occupy the A-sites in perovskite lattice. The dielectric constant and dielectric loss of barium strontium titanate based ceramics are obviously influenced by La2O3 as well as Sb2O3 addition content. The tetragonal-cubic phase transition of La2O3 modified barium strontium titanate ceramics is of second order and the Curie temperature shifts to lower value with increasing the La2O3 doping content. The phase transition of （La,Sb）-codoped barium strontium titanate ceramics diffuses and the deviation from Curie-Weiss law becomes more obvious with the increase in Sb2O3 concentration. The temperature corresponding to the dielectric constant maximum of （La,Sb）-codoped barium strontium titanate ceramics decreases with increasing the Sb2O3 content, which is attributed to the replacement of host ions by the Sb3＋ ions.

Dopant Behaviours of Sm_2O_3 on Microstructure and Properties of Barium Zirconium Titanate Ceramics

The effect of Sm 2O 3 dopant on the sintering characteristics and dielectric properties of barium zirconium titanate ceramics (BaZr x Ti 1- x O 3) was investigated. It is shown that trace amount of Sm 2O 3 can greatly affect the grain growth and densification of barium zirconium titanate ceramics during sintering. At the same time, the dielectric peak at high temperature shifts to lower temperature and that at low temperature shifts to higher temperature. The two dielectric peaks overlap with each other when the Sm 2O 3 dopant content varies from 0 25% to 1%, and the maximum relative dielectric constant is greatly enhanced. These effects may be attributed to the substitution actions of the rare earth element in perovskite lattice. At the doping content of 0 75%, the dielectric constant maximum of 23570 can be obtained. By adopting some proper additives, an excellent Y5V dielective material is obtained, and the room temperature properties are as follows: relative dielectric constant ε RT ≥23,000, dielectric loss tgδ≤0 0075 and the breakdown strength under alternating field E b≥5 kV·mm -1 .

Effects of Dysprosium Oxide Doping on Microstructure and Properties of Barium Titanate Ceramic

Different amounts of dysprosium oxide were incorporated into barium titanate powders synthesized by hydrothermal method. Relations of substitution behaviors and lattice parameters with solid-solubility were studied. Furthermore, the influences of dysprosium oxide doping fraction on grain size and dielectric properties of barium titanate ceramic, including dielectric constant and breakdown electric field strength , were investigated via scanning electron microscope, X-ray diffraction and electric property tester. The results show that dysprosium oxide can restrain abnormal grain growth during sintering and that fine-grained and high density of barium titanate ceramic can result in excellent dielectric properties. As mass fraction of dysprosium oxide is 0.6%, the lattice parameters of grain increase to the maximum because of the lowest vacancy concentration. The electric property parameters are cited as following： dielectric constant （25 ℃ ） reaches 4100, the change in relative dielectric constant with temperature is - 10% to 10% within the range of - 15 - 100 ℃, breakdown electric field strength （alternating current） achieves 3.2 kV·mm^-1, which can be used in manufacturing high voltage ceramic capacitors

Barium titanate ceramic inks for continuous ink-jet printing synthesized by mechanical mixing and sol-gel methods

Ink-jet printing of ceramic thick films is one of low cost on-site ceramic pattern fabrication methods.It is necessary to investigate the rheological behaviour of ceramic inks and drying behaviour of droplets.Two kinds of BaTiO3 ceramic inks were prepared by mechanical mixing and sol-gel methods,respectively.The effect of preparation parameters,such as quantity of polyacrylic acid(PAA)and solid content,on physicochemical and rheologic properties of the ceramic inks was investigated.The results show that they satisfy the requirements of continuous ink-jet printing.The appearances of printed dots and single printed layers were observed by SEM.The SEM images indicate that dots printed with mixing method ink are in ring shape,and dots printed with sol-gel method ink are in pancake shape,so the printed layer surface with the latter ink is smoother.The causes of these phenomena were discussed.

Dielectric properties and point defect behavior of antimony oxide doped Ti deficient barium strontium titanate ceramics

The microstructures and dielectric properties of Sb2O3-doped Ti deficient barium strontium titanate ceramics prepared by solid state method were investigated with non-stoichiometric level and Sb2O3content by SEM,XRD and LCR measure system.It is found that with the increase ofδ,(Ba0.75Sr0.25)Ti1-δO3-2δceramics transform from single phase solid solutions with typical cubic perovskite structure to multiphase compounds while(Ba0.75Sr0.25)Ti0.998O2.996ceramics remain to be single-phase with the increasing Sb2O3content.The distortion of the ABO3perovskite lattice caused by VTi″″and VO..induces the drop of Curie temperature and the rise of relative dielectric constant in(Ba0.75Sr0.25)Ti1-δO3-2δceramics with increasingδvalue.The orientation of VO??elastic dipoles results in the domain-wall pinning and thus the reduction of the dielectric loss.With increasing Sb2O3content,the relative dielectric constant,dielectric constant maximum and Curie temperature of(Ba0.75Sr0.25)Ti0.998O2.996ceramics decrease dramatically while the dielectric loss increases.

Structural and Dielectric Properties of Sn Doped Barium Magnesuim Zirconium Titanate Perovskite Ceramics

Perovskite type ceramics (Ba0.9Mg0.1)(SnxZr0.4-xTi0.6)O3 (with x = 0.01, 0.02, 0.03 and 0.04) relaxor composition prepared through solid state reaction route and calcinated at temperature is 1150°C for 5 hrs with intermediate mixing. The room temperature XRD study suggests that all the samples have the single phase cubic symmetry with space group pm 3 m. The pellets were sintered at 1500°C for 4 hrs. Scanning Electron Microscope (SEM) observations revealed enhanced micro structural uniformity and retarded grain growth with decreasing Sn content. The dielectric measurements at constant frequency show that dielectric constant increases with Sn content. Loss factor and dielectric constant decreased with increasing frequency but at very high frequencies it was independent.

Frequency-dependent ferroelectric and electrocaloric properties in barium titanate-based ceramics based on Maxwell relations

In this work,the frequency dependence of ferroelectric and electrocaloric properties in barium titanate-based ceramics was studied based on Maxwell relations.It is found that the maximum and remnant polarization will decrease while the coercive field increases a lot with rising frequency from 0.1 to 10 Hz,indicating that polarization rotation and domain switching become difficult at high frequencies.The electrocaloric properties show the different frequency dependence at different phase structures.Isothermal entropy change(ΔS)and adiabatic temperature change(ΔT)are similar around/above Curie temperature(TCT,showing tiny frequency dependence.However,ΔS andΔT display the obvious frequency dependence below T_(C),especially in the orthorhombic–tetragonal phase-transition region with a stable ferroelectric phase,and this frequency dependence becomes more obvious under a low-electric field.It is also found that increasing the frequency can weaken the electric field dependence of electrocaloric strength.This work gives a general profile of frequency dependence for electrocaloric properties in ferroelectric ceramics.

Temperature/electric field induced photoluminescence-modulation effect in dysprosium-doped barium titanate ferroelectric ceramics

Lanthanide(Ln^(3+))based ferroelectric phosphors,with an integration of PL emission and ferroelectric effect,are unveiling an exciting realm of possibilities for multifunctional ferroelectric-optic materials.However,how the ferroelectric host enables the tuning on the PL emissions through modulating the local structure(e.g.,lattice site,symmetry,strains etc.)of the Ln^(3+)activator is not established yet.In this work,a luminescent-ferroelectric material,i.e.Dy^(3+)doped BaTiO_(3) ceramic(Ba_(1–x)Dy_(x)TiO_(3)(x=0–0.07),abbr:BTO:Dy^(3+)),was explored to address the aforementioned issues.The BTO:Dy^(3+)ceramics were synthesized by a solid-state reaction method.The crystal structure,photoluminescence(PL)and electric properties(dielectric constant,ferroelectric hysteresis and piezoelectric hysteresis loop)were systematically investigated.The BTO:Dy^(3+)ceramics show two predominant emission peaks,corresponding to the blue magnetic dipole transition(477 nm,^(4)F_(7/2)→^(6)H_(15/2))and yellow electric dipole transition(573 nm,^(4)F_(7/2)→^(6)H_(13/2)),the intensity ration of which can be modulated by the ferroelectric polarization that causes the slight lattice deformation.Such a polarization-emission modulation combining with the Dy^(3+) doping could accelerate the color change,from yellow to blue,which is characterized to detect the phase transition,with a method and mechanism were proposed,that is,the phase change is reflected by the PL characteristic peak intensity ratio.Therefore,the current results offer a convenient photoluminescence method for detecting the ferroelectric phase transition and a feasible approach to study the interaction between the photoluminescence and polarization in ferroelectric materials,for providing new insights for the development of multifunctional materials.

Influence of Composition on Properties of Medium Temperature Sintering (Ba,Sr)TiO_3 Series Capacitor Ceramics

The influence of the composition （Yb2O3, MgO, CeO2, Li2CO3） on the dielectric properties of medium temperature sintering （Ba, Sr）TiO3 （BST） series capacitor ceramics was investigated by means of conventional technology process and orthogonal design experiments. The major secondary influencing factors and the influencing tendency of various factor＇s levels for the dielectric properties of BST ceramics were obtained. The optimum formula for maximum dielectric constant （ε） and for minimum dielectric loss （tanδ） was obtained under the experimental conditions. The BST ceramics with optimum comprehensive properties was obtained by means of orthogonal design experiments, with the sintering temperature at 1200 ℃, the dielectric constant 5239, the dielectric loss 0.0097, withstand electric voltage over 6 MV·m^-1, capacitance temperature changing ence of various components on the providing the basis for preparation rate （△C/C） - 75.67%, and suited for Y5V character. The mechanism of the infludielectric properties of medium temperature sintering BST ceramics was studied, thus of multilayer capacitor ceramics and single-chip capacitor ceramics.

Influence of Composition on Properties of BNT-BT Lead-Free Piezoceramics

Lead-free piezoelectric ceramics of (Bi1/2Na1/2)TiO3-BaTiO3(BNT-BT) were prepared by the conventional piezoelectric ceramic preparation technique (free air atmosphere sintering). The influence of BaTiO3 additive amount and La2O3 additive amount on the properties of BNT-BT lead-free piezoceramics were investigated. The results show that the dielectric constant(ε) and piezoelectric strain constant(d33) of materials start increasing and then decreasing while BaTiO3 additive amount increasing, the e and d33 of materials have maximum value (ε= 1650, d33 = 120 PC·N -1 ) while x (BaTiO3) =0.06 mol. Theεand d33 of materials start increasing and then decreasing while La2O3 additive amount increasing, the e and d33 of materials have maximum value (ε= 1684, d33 = 153 PC·N-1) while w(La2O3) =0.3% . The influence of La2O3 additive amount on the microstructure of BNT-BT piezoelectric ceramics was analysed by SEM( scanning electron microscope). The influence mechanism of La2O3 additive amount on the properties of BNT-BT piezoelectric ceramics was discussed. The BNT-BT ceramics with optimum comprehensive properties were obtained.

Effect of SiO_2 addition on the dielectric properties and microstructure of BaTiO_3-based ceramics in reducing sintering

The effect of SiO2 doping on the sintering behavior, microstructure, and dielectric properties of BaTiO3-based ceramics has been investigated. Silica was added to the BaTiO3-based powder prepared by the solid state method with 0.075mol%, 0.15mol%, and 0.3mol%, respectively. The SiO2-doped BaTiO3-based ceramic with high density and uniform grain size were obtained, which were sintered in reducing atmosphere. A scanning electron microscope, X-ray diffraction, and LCR meter were used to determine the microstructure as well as the dielectric properties. SiO2 can form a liquid phase belonging to the ternary system of BaO-TiO2-SiO2, leading to the formation of BaTiO3 ceramics with high density at a lower sintering temperature. The SiO2-doped BaTiO3-based ceramics can be sintered to a theoretical density higher than 95% at 1220℃ with a soaking time of 2 h. The dielectric constants of the sample with 0.15mol% SiO2 addition sintered at 1220℃ is about 9000. Doping with a small amount of silica can improve the sintering and dielectric properties of BaTiO3-based ceramics.

Dielectric Properties and Structure of Yb_2O_3-Doped (Ba,Sr)TiO_3 Ceramics

The effect of Yb2O3 doping amount on the dielectric properties of (Ba, Sr)TiO3 (BST) series capacitor ceramics prepared using solid state reaction method were studied. With the increasing of Yb2O3 doping amount, the dielectric constant(ε) of materials increased, the dielectric loss(tanδ) of materials decreased to minimum when w(Yb2O3) was 0.9%. The BST ceramics with high ε(10000), low tanδ(0.0213) and high DC breakdown voltage(7.2 kV·mm-1) were obtained. The influence of Yb2O3 doping amount on the structure of BST ceramics was studied by means of X-ray diffraction(XRD) and scanning electron microscope. The influencing mechanism of Yb2O3 on the dielectric properties of BST ceramics was studied. The results showed that Yb2O3 doping influenced the properties and structure of BST ceramics by means of forming defect solid solution, but did not influence crystal grain size,the crystal phase was single perovskite structure, did not influence XRD data of BST and did not improve capacitance temperature property greatly, but increase dielectric constant greatly. These results provided the basis for Yb2O3-doped BST series capacitor ceramics.

Impedance Spectroscopy of Ion Beam Mixed Cu/BaTiO_3 PTCR Ceramics

The positive temperature coefficient resistance ( PTCR) barium titanate ceramic samples have been prepared by the standard solid-state reaction method, and the ceramic samples have been treated by depositing copper films with magnetron sputtering method. The metallic copper films deposited on the ceramic substrates have been mixed at room temperature with argon ions in energy of 400 keV. Ion beam mixing induced modification of PTCR behavior of the ceramics was studied by using the ac complex impedance method and the resistance vs. temperature measurements . The results showed that room temperature resistance dramatically decreased and Curie point shifted toward higher temperature side for the ion beam mixed samples.

Preparation and Characterization of La<SUB>2</SUB>O<SUB>3</SUB>Doped Ba<SUB>0.3</SUB>Sr<SUB>0.7</SUB>TiO<SUB>3</SUB>Perovskite Ceramics of Varied Sintering Temperature and Doping

In order to explore new application opportunities of Barium Strontium Titanate (BST) ceramic composite by modifying the conventional ferroelectric properties of BST through La2O3 doping in BST matrix sintered at different temperature was investigated in this current study. Unadulterated Ba0.3Sr0.7TiO3 (BST) matrix was prepared from BaTiO3 (99.95%) and SrTiO3 (99.95%) taken in stoichiometric extents which later doped by La2O3 (99.99%) in varying extents (0.05 g, 0.10 g and 0.15 g) exploiting solid state reaction route. Doping caused drag effect for the penetration of impurities and sintering temperature helped the impurities migration to BST. Dielectric constant gets lower with rising of frequency, as electrons do not get enough time to polarize at high frequency. Dielectric constant and conductance are found maximum for the sample (0.1 g La2O3 doped BST) sintered at 1460°C and reverse is found in impedance analysis. These electrical properties showed visible frequency dependent response irrespective of sintering temperature and doping.

Glass modified barium strontium titanate ceramics for energy storage capacitor at elevated temperatures

A glass with composition of B_(2)O_(3)-Bi_(2)O_(3)-SiO_(2)-CaO-BaO-Al_(2)O_(3)-ZrO_(2)(BBSZ)modified Ba_(x)Sr_(1-x)TiO_(3)(BST,x=0.3 and 0.4)ceramics were prepared by a conventional solid state reaction method abided by a formula of BST+y%BBSZ(y=0,2,4,7,and 10,in mass).The effect of BBSZ glass content on the structure,dielectric properties and energy storage characteristics of the ceramics was investigated.The dielectric constant reduced but the endurable electrical strength enhanced due to the BBSZ glass addition in BST ceramics.In particular,the dielectric loss of the ceramics at elevated temperature(e.g.200℃)can be strongly suppressed from tanδ>20%to tanδ<3% after BBSZ glass modification.For Ba_(0.3)Sr_(0.7)TiO_(3)+2%BBSZ ceramics,an optimized energy storage density(γ=0.63 J/cm^(3))and efficiency(η=91.6%)under an applied electric field of 160 kV/cm was obtained at room temperature.Meanwhile,the temperature dependent polarization-electric field(P-E)hysteresis loops were measured to evaluate the energy storage characteristics of the ceramics potential for high voltage capacitor application at elevated temperatures.

光固化3D打印制备高性能BaTiO_(3)压电陶瓷

光固化3D打印技术在制备异形压电陶瓷方面具有广阔的应用前景。本文采用数字光处理技术制备了钛酸钡(BaTiO3)压电陶瓷,研究了坯体形貌、烧结温度对钛酸钡微观结构的影响。结果表明,曲拉通X-100的引入使陶瓷料浆的黏度小于3 Pa·s,同时陶瓷粉体的引入未改变树脂的性质。陶瓷坯体层间结合良好,且无明显缺陷。烧成后的BaTiO_(3)陶瓷内部含有四方与正交两种晶相,剩余极化强度为27.6μC/cm^(2),矫顽场为4.6 kV/cm,相对介电常数为2512,介电损耗为0.0091,居里温度为167℃,介电常数为182 pC/N。

MgNb_(2)O_(6)掺杂(Ba,Sr)TiO_(3)基电容器陶瓷介电性能的研究

采用固相法制备MgNb_(2)O_(6)(MNO)掺杂(Ba_(0.79)Sr_(0.21))TiO_(3)((Ba,Sr)TiO_(3))基电容器陶瓷。采用XRD、SEM等研究了MgNb_(2)O_(6)掺杂对(Ba,Sr)TiO_(3)基电容器陶瓷的物相、显微结构及介电性能影响。结果表明,随着MNO掺杂量的增加,(Ba,Sr)TiO_(3)基电容器陶瓷的介电常数逐渐减小,陶瓷的介电损耗先增大后减小再增大,陶瓷的电阻率先减小后增大再减小,陶瓷的耐压强度先减小后增大再减小。当MNO掺杂量(质量分数)为2.0%时,陶瓷的介电常数达到最大值(为1670),陶瓷的介电损耗有最小值(为0.0056)。当MNO掺杂量(质量分数)为8%时,陶瓷的电阻率有最大值(为65.23×10^(10)Ω·cm),耐压强度的最大值为7.7 kV/mm(DC)。当掺杂MNO量(质量分数)为10%时,陶瓷的电容温度变化率为+0.18%,-28.29%。MNO掺杂(Ba,Sr)TiO_(3)基电容器陶瓷是钙钛矿结构。掺杂MNO能够降低陶瓷的电容温度变化率。

Bi_(2)(SnO_(3))3掺杂(Ba,Sr)TiO_(3)介电陶瓷介电性能的研究

通过传统固相法制备Bi_(2)(SnO_(3))_(3)(BSO)掺杂(Ba_(0.79)Sr_(0.21))TiO_(3)((Ba,Sr)TiO_(3),BST)陶瓷。采用XRD、SEM等研究了Bi_(2)(SnO_(3))_(3)(BSO)掺杂对BST陶瓷的物相和微观结构及介电的性能影响。实验结果表明:随着BSO掺杂量增加,BST基介电陶瓷的介电常数开始增大而后减小然后再增大随后再减小,陶瓷的介质损耗首先增大然后减小。当掺杂BSO的量是2 wt%的时候,BST基介电陶瓷具有较好的介电性能:介电常数是5430;介质损耗是0.0145,电容温度变化率是+20.64%,-45.58%。BSO掺杂的BST基介电陶瓷仍为钙钛矿结构。BSO的掺杂起到移峰和压峰的作用。

掺杂钛锡酸钡基陶瓷的制备及电性能研究

采用固相合成工艺制备了Li-Al(简称LA)掺杂Ba1-x(LA)x(Ti_(0.91)Sn_(0.09))O_(3)-0.6%MnO_(2)陶瓷,研究了LA掺杂量对钛锡酸钡基陶瓷物相组成、相对密度、晶粒尺寸、介电性能和压电性能的影响。结果表明,LA掺杂钛锡酸钡基陶瓷都为ABO3型钙钛矿结构,(022)和(200)晶面的衍射峰会随着掺杂量增加而逐渐右偏移;随着掺杂量x从0增加至2.5%,LA掺杂钛锡酸钡基陶瓷的相对密度先增后减,在x=0.5%时取得最大值(93.7%)。相同频率下LA掺杂钛锡酸钡基陶瓷的介电常数从大至小顺序为:0.5%>1.0%>0>1.5%>2.0%>2.5%;LA掺杂量为0.5%时钛锡酸钡基陶瓷的介电常数最高。随着LA掺杂量从0增加至2.5%,压电系数d33、平面机电耦合系数Kp和相位角θmax都表现为先增后减趋势,在x=0.5%时取得最大值。x=0~1.0%时LA掺杂钛锡酸钡基陶瓷具有较好的压电温度稳定性和较高的退极化温度。钛锡酸钡基陶瓷中适宜LA掺杂量为0.5%。

BaTiO_(3)基超薄层BME MLCC的可靠性机理

多层陶瓷电容器(Multilayer ceramic capacitors,MLCC)作为市场占有率最高的无源电子元器件,是基础电子元件产业中需要突破关键技术的重点产品之一,在汽车电子、5G通讯、电网调频、航空航天等领域有广泛的应用。在小型化、薄层化发展趋势下,MLCC的介质层厚度不断降低,单层介质在相同电压下的电场显著增大,尤其是中高压超薄层MLCC。因此,MLCC的可靠性愈发成为一项关键的产品质量指标。本文结合加速老化测试、高温阻抗谱、漏电流测试,系统研究超薄层MLCC的劣化机理,揭示抑制氧空位的迁移与富集是保证超薄层MLCC可靠性的重中之重。为此,应减小介质层内部的氧空位浓度,增大其迁移所需的激活能,提高界面肖特基势垒,从而提升超薄层MLCC的可靠性。本文的研究成果为超薄层MLCC介质材料的设计提供了有力指导。