高纯超细钛酸钡的研制

介绍了一种用草酸共沉淀法合成高纯超细钛酸钡（ＢａＴｉＯ３）的方法，并对影响最终产品性能的几个主要因素，如加料速度，配料比，洗涤情况，干燥煅烧条件等进行了探讨，指出通过控制工艺条件完全可以稳定地制备出纯度〈９９．５％，粒度不超过１μｍ的球形钛酸钡。     

高纯超细钛酸钡的研制

介绍了一种用草酸共沉淀法合成高纯超细钛酸钡（ＢａＴｉＯ３）的方法，并对影响最终产品性能的几个主要因素，如加料速度、配料比、洗涤情况、干燥煅烧条件等进行了探讨．指出通过控制工艺条件完全可以稳定地制备出纯度＞９９．５％、粒度不超过１μｍ的球形钛酸钡。     

钛酸钡的制备研究进展

对钛酸钡粉末的制备方法进行了综合。传统的高温固相合成法已不能满足电子技术微型化和集成化发展对钛酸钡粉体提出的超细、高纯、单分散要求。从制备成本和操作过程来看，经过改进的共沉淀法、草酸盐法和水热法是制备高纯、亚微米级钛酸钡粉末的重要方法，在大规模生产中有较好的应用前景。在水热过程中，通过选择适当的钛源和水热条件，可以制备出高纯、单分散的亚微米级及纳米级钛酸钡粉体。低温直接合成法因其原料易得，过程简单，是一种在大规模生产上较有应用前景的制备纳米钛酸钡的方法。     

钛酸钡介电陶瓷制备方法及其掺杂改性研究进展

钛酸钡是一种重要的新型功能陶瓷材料,具备很高的介电常数和折射率常数,良好的热稳定性和压电性能,可以用来制造光电和介电材料。为了提高钛酸钡在室温下的介电常数使其得到广泛的应用,通常在钛酸钡中加入一些其他物质对其进行改性研究。在对钛酸钡材料常用的制备方法介绍的基础上,结合研究实际,重点综述了其掺杂改性的研究现状。只有不断开发钛酸钡材料新的制备方法并对其进行改性研究,才能使其性能不断提高,应用更为广泛。     

乙醇热法合成纳米钛酸钡及其形成机理的研究

研究了常压下以偏钛酸和氢氧化钡为原料，乙醇为溶剂制备纳米钛酸钡粉末的工艺条件。结果表明反应原料的钡钛比1.0：反应温度79℃；反应时间6h；pH值11为最佳制备条件．通过对在最佳条件下所得产物的XRD分析，表明钛酸钡粉体为立方相，a值约为4．028,TEM分析表明，分散的钛酸钡纳米粒子呈方形，平均粒径约20nm；ED分析表明，钛酸钡纳米粒子为多晶结构，其中有少量的单晶存在，通过对不同反应时间合成的产物的XRD分析，认为本法合成的钛酸钡为原位转变形成机理。     

纳米BaTiO3粉体制备技术的研究进展及展望

本文对目前合成纳米钛酸钡粉体的主要方法进行了综述,详细介绍了各种制备方法,并分析了它们的优缺点,指出了纳米钛酸钡粉体合成未来发展的方向是在对合成BaTiO3纳米颗粒的过程机理进一步深入研究的基础上,改善工艺条件,研制、开发高产率、高质量且低成本的工业化设备。     

水热法合成四方相超细BaTiO3粉体的研究进展

近年来，水热法合成四方相钛酸钡是一个研究热点问题，主要综述了水热法合成四方相钛酸钡粉体的研究进展，指出目前关于四方相和立方相相变的机理尚不完全清楚，临界尺寸还有待于进一步证实，四方相及其含量的测定还依赖于更为先进的设备和测试方法。     

微波法制备纳米钛酸钡粉体及其表征

为了探寻价廉、高效合成纳米钛酸钡粉体的方法,以TiCl4和BaCl2为主要原料,采用微波法一步合成纳米钛酸钡粉体,采用X射线衍射谱、扫描电镜、漫反射吸收谱、介电损耗谱和热重-差热分析对钛酸钡粉体进行表征。结果表明,合成的钛酸钡粉体为纯的立方相纳米粉体,颗粒大小均匀,分散性好,晶粒度约为90 nm;纳米钛酸钡粉体的禁带宽度为3.4 eV,具有良好的介电性能;纳米钛酸钡粉体中立方相BaTiO3在1 000℃煅烧后才有部分转化成四方相BaTiO3,表现出良好的热稳定性。     

工艺参数对低温燃烧合成钛酸钡粉体的影响

低温燃烧合成(LCS)钛酸钡粉体的工艺是一种能够直接在低温合成四方相纳米钛酸钡粉的方法。在硝酸盐和柠檬酸体系中,以推进剂化学为理论依据,实验得出各反应物间的最佳摩尔配比,考察了前驱体溶液pH值等对反应过程和最终产物的影响。应用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)等对粉体的结构、形貌进行了分析。结果在300℃点火生成晶粒度在100nm左右无杂质相的四方相钛酸钡粉。     

壳核型聚苯胺/钛酸钡复合电流变材料的制备及表征

采用溶液聚合的方法,在经过硅烷偶联剂表面修饰的钛酸钡微粉表面原位聚合聚苯胺,得到聚苯胺/钛酸钡壳核结构(BaTiO3/PAn)的有机-无机复合粒子.借助SEM、XRD、FT-IR、DSC-TG等分析手段研究了复合粒子的形貌、结构及热性能.利用改装后的旋转粘度计分别对钛酸钡和聚苯胺/钛酸钡复合颗粒的电流变性能进行研究.结果表明利用硅烷偶联剂成功地在钛酸钡粒子表面接枝合成聚苯胺,聚苯胺/钛酸钡复合颗粒电流变液的电流变性能明显比纯钛酸钡的电流变性能有所提高.     

Preparation and properties of barium titanate glass-ceramics sintered from sol–gel-derived powders

Homogeneous Ba–Ti–B–Si, Ba–Ti–Al–Si and Ba–Ti–B gels have been successfully prepared by the sol–gel process. A novel method is presented for fabricating barium titanate glass-ceramics by sintering the gel powders with small barium titanate crystallites. The structural development, grain size, crystallization process and dielectric properties were systematically studied by differential thermal analysis, thermogravimetric analysis, X-ray diffraction techniques, scanning electron microscopy and dielectric measurements. The glass-ceramic samples were sintered at lower temperatures compared to the barium titanate ceramic sintering, and showed improved dielectric properties. It was found that the small size effect of the barium titanate grains on the dielectric constant in the glass-ceramics was quite evident. Ferroelectric hysteresis loop analyses were also performed to manifest the ferroelectric nature of the barium titanate grains in situ grown from the gels. This revised version was published online in November 2006 with corrections to the Cover Date.     

Synthesis of nm-sized barium titanate crystallites using a new LTDS method and their characterization

A new LTDS method was established to synthesize nm-sized barium titanate crystallites with particle sizes around 10 nm. This LTDS method was the following two features, i.e., (1) a heat of neutralization in a neutralization reaction between strong acid and base can be used as a driving force for a formation of barium titanate, and (2) barium titanate crystallites can be directly synthesized from Ti and Ba ions, not via intermediates. Therefore, using the LTDS method, it can be expected that there is no minimum limit in particle sizes, and also no contamination in barium titanate crystallites. At first, optimum conditions for a formation of barium titanate were screened at various reaction temperatures and Ba/Ti atomic ratios in the starting materials. As a result, the formation of barium titanate was found at higher reaction temperatures than 50°C and higher Ba/Ti atomic ratios than 5. Under a constant temperature, particle sizes decreased with increasing Ba/Ti atomic ratios while under a constant Ba/Ti atomic ratio, particle sizes were independent of reaction temperatures. Finally, barium titanate crystallites with particle sizes below 10 nm were first prepared. These particles were also characterized using various methods.     

Characterization of dielectric barium titanate powders prepared by homogeneous precipitation chemical reaction for embedded capacitor applications

Various articles have reported that a highly pure and uniform form of barium titanate can be prepared by homogeneous precipitation. However, most of these works emphasize the mechanism of thermal decomposition of barium titanyl oxalate tetrahydrate, and only a few have discussed morphology or particle size. The morphology and particles size of barium titanyl oxalate tetrahydrate are governed by reaction temperature, pH value and solvent ratio; the barium titanate structure can be obtained by calcinating barium titanyl oxalate tetrahydrate above 600 °C or hydrothermally in a basic solution at 200 °C. The final morphology of barium titanate in this investigation was similar to that of barium titanyl oxalate tetrahydrate and the particle size of barium titanate increased with the calcination temperature. Using this barium titanate in a polymer/ceramic composite provided better dielectric characteristics than commercial ceramic powders use in embedded capacitor applications.     

Molten salt route of single crystal barium titanate nanowires

Rather long barium titanate nanowires have been synthesised by molten salt method without any organic surfactants. The crystal structure of barium titanate nanowires is identified by X-ray diffraction to be the tetragonal structure phase, Raman spectroscopy and selected area electron diffraction measurements. Furthermore, scanning electron microscopy and transmission electron microscopy observations show that the barium titanate nanowires have uniform cylindrical structure, with lengths from 20 to 80 μm and diameters from 100 nm to 1 μm. Moreover, high resolution transmission electron microscopy observations and selected area electron diffraction analysis show that the barium titanate nanowires are single crystals with a tetragonal structure in nature.     

Flash and Breakdown: Thermal Runaway and Dielectric Breakdown as Competing Mechanisms During Flash Sintering of Barium Titanate

Herein, hot-spot generation in bulk barium titanate samples is investigated during controlled current ramping at various rates using in situ dilatometry. The incubation of the flash event is separated from dielectric breakdown at high current densities, which has previously been attributed to cause flash incubation in barium titanate. The lower boundary of the onset temperature of the flash event in barium titanate is investigated through conventional flash experiments at high electric fields. Despite incubating through thermal runaway, the lower boundary does not coincide with the Debye temperature of barium titanate.     

Preparation and Properties of Barium Titanate Nanopowder/Epoxy Composites

This article is focused on the preparation of barium titanate nanopowder/epoxy composites and studying the effect of barium titanate nanopowder on improving mechanical and thermal characteristics of the epoxy polymer. Composites are prepared by dispersing barium titanate nanopowder in epoxy resin and, subsequently, cross-linking by using diamino diphenyl methane (DDM) curing agents. Synthesis of barium titanate nanopowder/epoxy composites is carried out for different concentrations (1, 3, and 5 by weight) of barium titanate nanopowder at high temperature. High-temperature curing (HTC) involves mixing the resin-nanopowder solution followed by DDM hardener and curing at 120°C. Tensile, flexure, and impact results showed a maximum value of 72.7 MPa, 2.98 GPa, and 2 J/cm, respectively. DSC analysis revealed that curing occurs at low temperature in the presence of barium titanate nanopowder. Thermogravimetry analysis (TGA) showed the increased thermal stability in the nanoparticle filled epoxy composites as compared with the pure epoxy counterparts. Dynamic mechanical analysis (DMA) revealed, maximum storage modulus of 6400 MPa and glass transition temperature of 154°C for 3 wt% barium titanate nanopowder.     

Influence of microstructure on dielectric properties of Nd-doped barium titanate synthesized by hydrothermal method

Nd-doped barium titanates were successfully synthesized via a hydrothermal route. The as-prepared barium titanate was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transformation infrared spectroscopy (FTIR), and Vis–NIR spectroscopy respectively. The results show that pure and Nd-doped barium titanate powders have cubic perovskite structure. After sintering at a temperature of 1,250 °C for 2 h, the phase compositions of all barium titanate are tetragonal phase structure. Vis–NIR spectra well confirmed that Nd³⁺ have been doped into barium titanate. The particle diameters of Nd-doped barium titanate powders and ceramics become samller with the increase of Nd³⁺ content. When Nd/Ba molar ratio is 0.02, the dielectric loss (0.0008) of the powder measured at 1 MHz and room temperature dramatically decreases by 99 % comparing with pure barium titanate (0.083) and shows frequency independence with the frequency increasing from 40 Hz to 1 MHz. The dielectric constant and dielectric loss are 436 and 0.09 after sintering. The Nd-doped BaTiO₃ show an improvement in the dielectric quality which possess a decreased sensitivity to frequency for both the dielectric constant and dielectric loss. Such improvements are of potential importance for high energy density and low loss.     

Electrooptic modulation in thin film barium titanate plasmonic interferometers

We demonstrate control of the surface plasmon polariton wavevector in an active metal-dielectric plasmonic interferometer by utilizing electrooptic barium titanate as the dielectric layer. Arrays of subwavelength interferometers were fabricated from pairs of parallel slits milled in silver on barium titanate thin films. Plasmon-mediated transmission of incident light through the subwavelength slits is modulated by an external voltage applied across the barium titanate thin film. Transmitted light modulation is ascribed to two effects, electrically induced domain switching and electrooptic modulation of the barium titanate index.     

Selective laser sintering of barium titanate–polymer composite films

A selective laser sintering process has been used to consolidate electro-ceramic thin films on silicon substrates. Methods of forming pre-positioned layers of barium titanate were investigated by spin-coating the feedstock powder mixed with a commercial polymer photo-resist. The ceramic–polymer composite was deposited directly onto a nickel film which was evaporated onto a silicon substrate, pre-oxidised to form an electrically insulating layer. A range of laser processing parameters was identified in which consolidated barium titanate layers could be formed. The laser power was found to be more influential in forming sintered microstructures than laser exposure time. The microstructure of barium titanate films is sensitive to the SLS laser-processing conditions, with the optimum laser powers for the processing of the BaTiO₃–polymer found to be in the range 17–20 W. This article highlights the possibility of using ‘direct write’ techniques to produce piezoelectric materials upon silicon substrates.     

高性能钛酸钡/聚合物复合材料的研究进展

具有高介电常数(k)的钛酸钡/聚合物复合材料,兼有钛酸钡陶瓷和聚合物的各自优势,是一种有广泛应用前景的电子材料,因而备受关注。综合给出了近5年来高性能钛酸钡/聚合物复合材料的研究进展,分析指出了原材料选择、制备工艺及其对复合材料介电性能的影响,概括介绍了这类复合材料的主要应用,预测展望了其未来的发展趋势。