SrTiO3陶瓷晶界层电容器材料的晶界研究Ⅰ.晶界结构

利用高分辨电镜研究了低温一次烧结SrTiO_3陶瓷晶界层电容器材料的晶界结构,发现在西晶粒间存在着4种典型的晶界类型。通过构筑晶界形成的结构模型,揭示了两晶粒间晶界形成的特征,认为两晶粒间晶界相的形成既与两晶粒间的液相成份和杂质组成有关,亦与两晶粒的相对取向有关。此外,还与两次烧结SrTiO_3陶瓷晶界层电容器材料的晶界结构作了比较。     

钛酸酯偶联剂NDZ-311湿法改性重钙的研究

采用异丙醇溶解的钛酸酯偶联剂NDZ-311对重钙进行超声湿法表面改性，改性后重钙粉体的活化指数达最大值98．9％，吸油值由改性前的0．69mL／g下降到0．51mL／g，分散于50mL液体石蜡中形成的分散相在静置3h后其体积依然保持在48mL以上，稳定性较好。采用DSC和FT—IR方法对改性重钙进行分析表明，超声条件下改性剂与重钙表面发生了化学反应或键合。     

基于人工神经网络的BaTiO3陶瓷配方研究

人工神经网络具有巨量并行、结构可变、变度非线性等特点，其建立数学模型并不需要预先知道太多有关问题背景的知识，这尤其适用于陶瓷配方研究中某些机理尚未完全清楚、传统数学方法无法分析的情况，本工作将人工神经网络技术用于介电陶瓷的配方性能分析，以BaTiO3为研究对象选取了几种掺杂剂，在均匀实验设计的基础上，用BP人工神经网络对所得实验结果进行了分析，并且用图形化方式直观地表达了出来，根据实验结果，并与多重非线性回归模型相比发现，人工神经网络模型比多重非线性回归模型更加准确且能给出配方组成与性能更丰富的信息，这对于研究各组分作用规律并获得介电陶瓷多性能指标的优化配方具有重要的指导作用。     

Electrical Properties of Sr0.7Ba0.3TiO3 Ceramics Doped with Nb2O5, 3Li2O · 2SiO2, and Bi2O3

The electrical properties of Sr_0.5Ba_0.3TiO₃ in the presence of Nb₂O₅ as a donor, 3Li₂O · 2SiO₂ as a sintering agent, and Bi₂O₃ as a dopant have been studied. When the compositions of the ceramics were 1 mol Sr_0.7Ba_0.3TiO₃+ 0.5 mol% Nb₂O₅+ 2 mol% 3Li₂O · 2SiO₂+ 0.2 mol% Bi₂O₃, the ceramics were sintered at 1100°C and exhibited the following characteristics: apparent dielectric constant ɛ, 25000; loss factor tan δ, 2%; insulating resistivity ρ_j, 10¹⁰Ω· cm; variation of dielectric constant with temperature Δɛ/ɛ (−25° to +85°C), +10%, −14%. ɛ and tan δ show only small changes with frequency. The study shows this ceramic can be used in multilayer technology.     

Jonker "Pecir" Analysis of Oxide Superconductors

Data for the normal state of the superconducting oxide systems YBa₂Cu₃O_6+y, and the nonsuperconducting system La₃Ba₃Cu₆O_12.5+y, when plotted as thermoelectric coefficient versus logarithm of conductivity, exhibit Jonker "pear" behavior, confirming the semiconducting character of these materials. The symmetry of the plots indicates similar conduction parameters (density-of-states (DOS), transport constants, and mobilities) for p - and n -type mechanisms. Band gaps on the order of 0.5 eV are obtained. DOS—mobility products for the above-mentioned systems and La_2-xBa_xCuO₄ and Bi₂Sr₂CaCu₂O₈ scale roughly according to the density of copper ions in these materials and fall in the range 10²⁰ to 10²¹ (cm·V·s)⁻¹. Assuming DOS equal to copper content results in mobilities on the order of 0.15 cm²·V⁻¹· s⁻¹. These results are discussed in terms of possible semiconduction mechanisms.     

Direct hydrothermal synthesis and magnetic property of titanate nanotubes doped magnetic metal ions

Pure titanate nanotubes and titanate nanotubes doped with Fe3 /Ni2 /Mn2 ions were synthesized by the hydrothermal method. In this process, titanate nanotubes were first prepared synchronously with doping Fe3 /Ni2 /Mn2 ions. The morphology,structure, thermal stability and magnetic property of titanate nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), and magnetic measurement. The titanate nanotubes transformed into the anatase titania nanocrystals,and further the mixture of anatase and rutile titania along with increasing temperature. The results indicate that the titanate nanotubes doped with Fe3 /Ni2 /Mn2 ions are paramagnetic behaviors.     

Synthesis of PZT power by wet-dry method and its structure

To prepare PZT powder at lower temperature, lead zirconate titanate (PZT) powder (x(Zr)/x(Ti)=56?44) was prepared by wet-dry method. Glycol was used as the solvent, and zirconium oxychloride was used as zirconium source. The properties and structure of the powder were analyzed by XRD, SEM and Sedimentograph. The effects of sintering parameter such as sintering temperature, keeping time and heating-up velocity on structure of PZT power were investigated. The results show that homogeneous PZT with single-phase perovskite structure can be obtained after sintering at 730 ℃ for 2 h, and the average size of PZT powder is about 113 nm.     

氧化铝-钛酸铝复相陶瓷的抗热震性能

为了提高氧化铝陶瓷的抗热震性,将具有低膨胀系数的钛酸铝加入到Al₂O₃中,通过无压烧结工艺,制备出了氧化铝-钛酸铝复相抗热震陶瓷.结果表明,钛酸铝加入量为w(钛酸铝)=20%,烧结温度为1510℃时,陶瓷样品能够承受1500?℃温差(空冷)的热震破坏,并且是制备氧化铝-钛酸铝复相陶瓷的最佳成分.采用SEM对陶瓷进行组织结构分析,发现在基体内部形成长柱状固溶体,并呈无规则分布状态.这样的显微组织有利于缓解热应力和提高强度,对提高陶瓷的抗热震性具有重要作用.     

Synthesis of Bismuth Sodium Titanate Nanosized Powders by Solution/Sol–Gel Process

(Bi_1/2Na_1/2)TiO₃ (BNT) is a prominent candidate for a lead-free piezoelectric material. In this study, BNT was synthesized using the solution/sol–gel method, in which a solution of Bi₂O₃ and Na₂CO₃ was dissolved in HNO₃ as starting materials. The solution then was mixed with ethylene glycol and titanium tetraisopropoxide. The obtained BNT powder was analyzed using FT-IR, DTA-TG, Raman spectroscopy, and high-temperature XRD. Results showed that BNT crystallization occurred above 600°C. TEM investigation showed that 100–200 nm BNT particles were formed by heat-treating the sol–gel-derived BNT sol at 700°C for 6 h.     

Phase Homogeneity and Segregation in PZT Powders Prepared by Thermal Decomposition of Metal–EDTA Complexes Derived from Nitrate and Chloride Solutions

Fine, homogeneous lead zirconate titanate (PZT) powders have been prepared by the thermal decompostion of metalorganic complexes derived from nitrate solutions using ethylenediaminetetraacetic acid (EDTA) as a complexing agent. It has been shown that nitrate ions accelerate the decomposition of the precursor and the crystallization of the PZT phase initiates at temperatures as low as 250°C. No intermediate phases, other than PbO, were found. The coexistence region of the rhombohedral and tetragonal phases in the sintered ceramic was found to be a little over 1 at.%. The chloride-EDTA precursor did not form the desired PZT phase, even after calcination at 1000°C. The segregation and loss of lead was observed for this material, due to the formation and evaporation of PbCl₂. DTA/TGA, SEM, and XRD were employed to characterize the powders. The use of TEM with nanoprobe energy dispersive X-ray analysis (EDX), allowed the identification of the phase segregation in the chloride-EDTA derived powder. A possible reaction mechanism for this phase segregation is suggested.