钛酸锶钡铁电陶瓷材料掺杂改性研究进展

综述了最近几年国内外专家对钛酸锶钡(BST)铁电陶瓷材料的掺杂改性方面的研究情况,介绍了不同掺杂物对BST材料性能的影响,简述了BST陶瓷材料的应用趋势。论述了掺杂物掺杂改性材料的组成、结构和性能之间的关系,提出了研究中需要解决的一些问题,展望了钛酸锶钡电介质材料掺杂改性的发展方向。     

Mn和Zr共掺杂钛酸锶钡/氧化镁复合陶瓷材料的微结构和介电性能

通过固相反应法制备Mn、Zr共掺杂钛酸锶钡/氧化镁陶瓷粉体,经干压成型后在空气气氛中于1450℃烧结4h,通过扫描电子显微镜和X射线衍射研究了ZrO2和MnO2共掺杂的Ba0.6Sr0.4TiO3/MgO复合陶瓷材料的微结构和介电性能。结果表明:ZrO2可以显著降低材料的介电常数和介电损耗,有效提高了陶瓷材料的温度稳定性;随ZrO2添加量的增加,体系的晶胞参数略有增加,MgO在钛酸锶钡中以独立相的形式存在;制备出的BST铁电陶瓷材料的25℃相对介电常数较低(εr<110),介质损耗小于1.0×10–3(在频率为10kHz时),温度系数小于6.012×10–3,可调性大于20%(8.0kV/mm),适用于制作移相器。     

钛酸锶钡电介质材料的掺杂改性及其应用

综述介绍了国内外对于钛酸锶钡（strontium barium titanate,BSTO0电介质材料在掺杂改性方面的研究状况，介绍了MgO,Al2O3,ZrO2,CeO2,Dy2O3和La2O3等金属氧化物的掺杂对于BSTO陶瓷材料的介电性能的影响。论述了材料的组成，显微结构以及介电性能之间的关系，指出了该材料在移相器领域和存储器领域极负潜力的应用方向。     

掺杂氧化铌对钛酸锶钡铁电陶瓷材料显微结构和介电性能的影响

钛酸锶钡(barium strontium titanate,BST)铁电陶瓷材料的介电常数(ε)随外加直流电场的变化呈现非线性特性.纯BST材料由于较高的ε和较大的介电损耗(tanδ)不能满足移相器介质材料的要求.通过在BST中添加氧化铌(Nb2O5)来改善BST铁电陶瓷材料的介电性能.结果表明:在BST体系中微量掺杂Nb2O5,Nb5 以取代Ti4 的方式存在于钙钛矿的晶格中,形成均匀的固溶体Ba0.5Sr0.5Ti1-xNbxO3.随Nb5 添加量的增加,Curie峰逐渐变宽,峰高逐渐降低,相变弥散效应增强.Nb5 的掺杂能显著降低并稳定BST陶瓷的tanδ,改善BST体系的介电性能.     

钛酸锶钡基高压陶瓷电容器材料的研究

钛酸锶钡(Ba1-xSrxTiO3)材料既具有钛酸钡(BaTiO3)的高介电常数和低介质损耗,又具有钛酸锶(SrTiO3)结构稳定的特点,是非常理想的高压陶瓷电容器材料.本论文采用常规陶瓷电容器制备工艺,利用正交设计实验法研究了配方对Ba1-xSrxTiO3基高压陶瓷电容器介电性能的影响,得到了影响该系统陶瓷介电性能的主次因素以及各因素水平影响其性能的趋势,并讨论了Bi2O3·3TiO2、CaZrO3、Nb2O5和MgO改性添加物对材料性能的影响.通过正交实验得到了综合性能较好的钛酸锶钡基陶瓷配方,结果表明,在Ba1-xSrxTiO,(当x=0.4时)中加入8%Bi2O3·3TiO2、6%CaZrO3、0.6%Nb2O5和0.5%MgO时,其介电常数ε为3785、介质损耗tgδ为23×10-4、耐压强度Eb为11 kV/mm;而在Ba1-xSrxTiO3(当x=0.4时)中加入8%Bi2O3·3TiO2、10%CaZrO3、0.2%Nb2O5和1%MgO时,其ε为3416、tgδ为30×10-1、Eb为13.5 kV/mm.     

Ag~+掺杂钛酸锶钡基玻璃陶瓷的显微结构和介电性能

采用熔融法制备了钛酸锶钡（barium strontium titanate,BST）基玻璃,然后将此玻璃样品在不同的温度下进行热处理得到BST基玻璃陶瓷,采用差热分析研究了BST基玻璃陶瓷析晶过程中的热力学特征,用扫描电子显微镜和X射线衍射分别分析了玻璃陶瓷的显微结构和相结构,并且系统研究了该玻璃陶瓷的介电特性以及耐击穿电场强度。结果表明：0.3%（质量分数）Ag＋掺杂时,BST基玻璃中BST相的析晶温度从885℃下降到840℃,有利于玻璃体中BST晶体的析出。另外,Ag＋的掺杂有利于提高BST基玻璃陶瓷的介电常数,同时能维持较低的介电损耗。此外,Ag＋掺杂能够提高BST基玻璃的耐击穿电场强度,其在800℃热处理后,可达96.3 kV/mm,高于未掺杂Ag＋的BST基玻璃的52.5kV/mm。     

二氧化硅掺杂钛酸锶钡陶瓷的介电性能与电卡效应

采用传统的固相反应法制备二氧化硅（SiO₂）掺杂钛酸锶钡（Ba_0.65Sr_0.35TiO₃,BST）陶瓷（BST+x%SiO₂）,研究了掺杂二氧化硅对BST陶瓷的物相、微观形貌、介电性能及电卡效应的影响。结果表明：掺杂二氧化硅并未改变BST陶瓷的晶型结构,但有助于提升晶粒的均匀性和材料介电性能频率的稳定性。随着二氧化硅掺杂量增加,BST陶瓷的介电常数呈现单调递减趋势,介电弥散特性逐渐增强。二氧化硅的掺杂有利于提升BST陶瓷的电卡性能,其中BST+3%SiO₂陶瓷具有最优的电卡效应,在30 ℃下可获得最大电卡绝热温变（ΔT_max）,ΔT_max和ΔT_max/ΔE分别为1.6 ℃、8.00×10 ^-7 ℃·m/V,电卡效应半峰宽（T_span）为10 ℃左右。     

螯合剂对钛酸锶钡薄膜结构与性能的影响

采用阻抗分析、差热分析,X射线衍射、透射电镜等方法研究了．螯合剂对Ba0.5Sr0.5TiO3薄膜结构与性能的影响。当乙酰丙酮作为螯合剂时,它与Ti(COC4H9)4螫合形成网络骨架结构,Ba^2 ,Sr^2 均匀地分布在此网络中,热分解时金属离子能够均匀地分布,使钙钛矿的形成温度降低了约60℃。薄膜表面颗粒分布均匀,孔洞少,比较致密。晶粒的平均粒径均为80nm,晶格条纹间距约N0．296nm,晶界两侧的晶粒取向是随机的;畴的宽度约为1～2nm。薄膜具有较高的相对介电常数和较小的介质损耗。     

改性钛酸锶/PVDF复合材料介电性能研究

采用具有强络合能力的酒石酸在碱性溶液中对SrTiO3陶瓷颗粒进行表面改性,将改性后的SrTiO3颗粒与聚偏二氟乙烯(PVDF)经热压共混成型,制备出系列陶瓷/聚合物基复合材料,对改性SrTiO3/PVDF复合材料进行了介电性能分析。结果表明:添加了改性SrTiO3的复合材料比未改性SrTiO3复合材料的介电常数增加值达34%以上,同时,改性复合材料的介电损耗仍保持较低水平;随着改性SrTiO3在复合材料中含量的增加,介电常数也随之增加,介电损耗仍保持不变,改性后的陶瓷/聚合物复合材料表现出优异的综合介电性能。     

钛酸锶钡微晶玻璃的铈掺杂效应研究

通过X射线光电子能谱、紫外-可见漫反射光谱、傅里叶变换红外光谱和拉曼光谱研究了(Ba,Sr)TiO3微晶玻璃的铈掺杂效应.玻璃体系为BaO-SrO-TiO2-Al2O3-SiO2(Ce摩尔分数为0％、1％、2％、3％).随着Ce摩尔含量增加,Ce在(Ba,Sr)TiO3晶格中的占位从Ce4+取代Ti4+位的形式逐渐变成...     

Effect of Aliovalent Substituents on the Ferroelectric Properties of Modified Barium Titanate Ceramics - Relaxor Ferroelectric Behavior

Structure–property relationships were investigated to reveal the generic influence of various substituents on ferroelectric BaTiO₃. Compositional modifications of ferroelectric BaTiO₃ were systematically investigated for La³⁺ and Nb⁵⁺ substituents. A generic influence of charged point defects in breaking down the ferroelectric domains into polar clusters was demonstrated. In both types of modified BaTiO₃, relaxor ferroelectric behavior was induced for higher concentrations of substituents.     

钛酸锶钡结构与制备工艺研究进展

钛酸锶钡[(Ba,Sr)TiO3,SBT]是1种重要的电子陶瓷材料,具有高介电常数、低漏电流、高热释电系数,高的介电可调等特性,广泛用于动态随机存储器、热释电探测器、介质移相器等电子元件的制备。综述了钛酸锶钡[(Ba,Sr)TiO3,SBT]的结构和制备工艺研究进展,评述了制备工艺和掺杂等对钛酸锶钡的结构和性能的影响,并指出了钛酸锶钡尚待解决的问题。     

Grain-Boundary Chemistry of Barium Titanate and Strontium Titanate: I, High-Temperature Equilibrium Space Charge

Direct observations using scanning transmission electron microscopy (STEM) of the grain-boundary chemistry of selectively doped SrTiO₃ and BaTiO₃ show the predominant solute segregation in both systems to be that of acceptors (negative effective charge). Appreciable donor segregation is not observed even at lattice concentrations as high as 10 mol%. Donor and acceptor codoped materials show segregation of the acceptor only. The results are consistent with a grain-boundary space-charge distribution consisting of a positive boundary and negative space charge. All grain boundaries examined also show an excess of Ti relative to the A-site cations, suggesting that the positive boundary charge is at least partially accommodated by an excess of Ti ions. The sign and magnitude of the electrostatic potential appear to be remarkably insensitive to changes in lattice defect structure with solute doping. Grain-boundary chemistry appears dominated by space-charge segregation, in contrast with the predictions of recent atomistic simulations which neglect the space-charge potential.     

Phase Equilibria in the System Barium Titanate—Strontium Titanate

Phase equilibria in the system BaTiO₃–SrTiO₃ (with 0 to 7 mol% SrTiO₃) were studied at temperatures above 1600°C in air. Quenching experiments were performed using high-purity starting materials, and run products were examined by X-ray diffraction and differential scanning calorimetry to determine phase composition and Sr concentration. Melting involves a binary loop intersected by the invariant reaction hexagonal (Ba, Sr)TiO₃( ss ) ⇌ cubic (Ba, Sr)TiO₃( ss ) + liquid. In contrast with earlier work, these results indicate that there is no depression of the melting point with Sr addition and no congruent melting point in this compositional range.     

Flextensional Barium Strontium Titanate Actuators

This paper describes the performance of the cymbal flextensional transducer using Dy-doped barium strontium titanate (BST) as the driver material. BST was first characterized for its dielectric and loss behavior as a function of temperature and electrical bias field. With no electrical bias, the transition temperature was measured to be near 20°C and have a dielectric constant >20 000. The strain of a BST disk was then measured and compared with other ceramics. At room temperature the strain and average effective piezoelectric d ₃₃ of this non-lead composition was slightly larger than Navy type I lead zirconate titanate (PZT-4) ceramic. The strain/field behavior was also measured as a function of temperature. Cymbal capped BST ceramic was found to have an amplified displacement of 28×, also very similar to type I ceramic. The stiffness of BST was found to be tunable by dc voltage and 2 to 3 times larger than that of PZT. This material has promise for applications in actuators and transducers with large generative force.     

{111} Twin Formation and Abnormal Grain Growth in Barium Strontium Titanate

Two series of experiments were performed to study the experimental conditions for the formation of {111} twins and related microstructures in barium strontium titanate ((Ba, Sr)TiO₃). In the first series, the phase equilibria in the BaTiO₃–SrTiO₃–TiO₂ system were determined. XRD and WDS analysis, done in the BaTiO₃-rich region, of 45(Ba,Sr)TiO₃–10TiO₂ samples annealed at 1250°C for 200 h in air showed that (Ba,Sr)TiO₃ was in equilibrium with Ba₆Ti₁₇O₄₀ (B₆T₁₇) and Ba₄Ti₁₃O₃₀ phases with strontium solubility (Sr/(Ba + Sr)) of ∼0.02 and 0.20, respectively. In the second series the microstructures of samples consisting of a mixture of (Ba,Sr)TiO₃ and 2.0 mol% TiO₂, were observed after sintering at 1250°C for 100 h in air. {111} twins formed only in the samples with faceted B₆T₁₇ second phase particles, similar to the case of BaTiO₃. In these samples, abnormal grain growth occurred in the presence of the {111} twins. In contrast, no {111} twins formed and no abnormal grain growth occurred in the samples containing second phase particles other than B₆T₁₇. With an increased substitution of strontium for barium, the aspect ratio of abnormal grains containing {111} twin lamellae was reduced. This result was attributed to a reduction in the relative stability of the {111} planes with the strontium substitution.     

Dopant Effect on Local Dielectric Properties in Barium Titanate Based Electroceramics Determined by Transmission EELS

Local electronic excitations of Nb-doped BaTiO₃ electroceramic were investigated using low-loss electron energy loss (EEL) spectroscopy with a transmission electron microscope. The variations in electronic structure of the BaTiO₃ were monitored as a function of Nb content by using Kramers-Krönig analysis of the low-loss EEL spectra. We found that the valence state of Nb (+5) as compared with that of the Ti (+4) introduces changes in the valence and conduction band states of BaTi_{1− x} Nb _x O₃ samples. The real part of the dielectric function, Re(1/ɛ), displays an increasingly less negative character with higher amounts of dopant and the valence plasmon exhibits "quasi-plasmon" characteristics with the addition of Nb (at 0.0–1.8 at.%). Further, the plasmon energy shifts (by about 0.5 eV) to higher values with Nb additions. Significant changes take place in oscillator strengths of excitations in local (nanometer-scale) regions of the perovskite samples. This investigation demonstrates a method to quantitatively assess electronic properties, at the submicrometer scale, of doped ceramics used in electronic and electrooptical applications.     

Fluorine as a Donor Dopant in Barium Titanate Ceramics

We have studied the electrical properties and microstructure of fluorine-doped BaTiO₃ ceramics. The samples were prepared using a classical ceramic technology that involved the calcination of intimately mixed powders of BaCO₃, TiO₂, and BaF₂. When the samples were sintered in untreated ambient air, the fluorine from the sample reacted with water vapor and formed gaseous HF. To prevent this hydrolysis of the fluorine, we sintered the samples in dried air. The fluorine-doped BaTiO₃ ceramics sintered in a dry atmosphere showed microstructures and electrical properties typical of donor-doped BaTiO₃. The samples containing up to 0.3 mol% of fluorine were coarse-grained, semiconducting, and displayed a remarkable PTCR effect. In contrast, the samples with a higher fluorine concentration were fine grained and insulating. A SIMS elemental mapping of the samples showed that the fluorine was distributed throughout the microstructure of the semiconducting samples; however, the fluorine concentration was enriched at grain boundaries and in the BaTi₂O₅ intergranular phase.     

Low-Temperature Preparation and Size Effect of Strontium Barium Niobate Ultrafine Powder

Ultrafine strontium barium niobate ((Sr _x Ba_{1− x} )Nb₂O₆, SBN) powders were prepared using sol–gel and hydrolysis aging processes. Their structural properties were examined via X-ray diffractometry and Raman spectroscopy. Our results indicated that the SBN powders crystallize to a pure tetragonal phase at annealing temperatures as low as 700°C. The crystallite size of SBN powders subjected to different thermal treatments was in the range of several tens of nanometers. Differential scanning calorimetry revealed that the heat flow had a broadened peak. The transition temperature from the ferroelectric phase to the paraelectric phase and the relative dielectric constant of the SBN50 powder were less than the corresponding values of the bulk ceramic and the single crystal.