Vaporization of Lead Zirconate-Lead Titanate Materials

A thermogravimetric investigation of the vaporization of cold-pressed Pb(Zr_0.65Ti_0.35)O₃ in vacuum from 690° to 1130°C shows that the vaporization occurs in two steps. An initial loss of 1 to 7 wt% proceeds by a mechanism with a logarithmic time dependence and represents the vaporization of the unreacted PbO that remains after the initial calcining. The second step proceeds by a slower, diffusion-controlled mechanism with a parabolic time dependence. It is shown that this rate-determining step is bulk diffusion across a thickening lead-depleted layer in the cold-pressed pellet, despite pore volumes of 24 to 42%. The rate constant, g/cm² sec½, for the parabolic weight loss process is expressed by: log K = (3.37 ± 0.14) - (8.46 ± 0.16) (10³/ T _K). The activation energy is 38.7 ± 2.0 kcal/mole.     

Effect of Composition and Size of Crystallite on Crystal Phase in Lead Barium Titanate

Lead titanate, barium titanate, and lead barium titanate powders (>99.9% pure), the particle size of which varied from 0.03 to 0.15 μm depending on the calcination temperature and the composition, was prepared from barium lead titanyl oxalate, which was previously prepared by reacting high-purity ammonium titanyl oxalate with barium and lead acetate. The critical crystallite size of BaTiO₃ powder from the cubic to the tetragonal phase is around 1 μm. Pb_0.3Ba_0.7TiO₃ powder with an average size of 0.057 μm showed the tetragonal phase.     

倒车雷达用锆钛酸铅压电陶瓷材料的研究

对锆钛酸铅陶瓷材料进行了Nb2O5、SrCO3微量掺杂改性研究,观察了掺杂后陶瓷样品的显微结构,研究了其相对介电常数、压电常数、机电耦合系数及电容量变化率随测试温度变化的规律。实验结果表明:Nb2O5、SrCO3掺杂后,陶瓷结构致密,介电损耗减少,相对介电常数、压电常数、机电耦合系数明显提高,电容量变化率明显改善。当Nb2O5、SrCO3的添加量为0.6wt%时,制得的压电陶瓷材料具有最佳的压电性能:εr=2100,D33=450pC/N,Kp=0.81,ΔC/C10%(-55~85℃),可以满足高性能的汽车倒车雷达的应用要求。     

Thermal Depoling Effects on Anisotropy of Lead Zirconate Titanate Materials

Changes in elastic anisotropy and fracture toughness anisotropy of a lead zirconate titanate (PZT) piezoelectric material as a function of depoling temperature were investigated using ultrasound and Vickers indentation. A gradual transition from anisotropic to isotropic properties occurs with increased depoling temperatures at and above the Curie temperature. Depoling is also evident through changes in domain character revealed by X-ray diffraction. The relationship between the mechanical properties and domain structure variation with respect to different depoling conditions is discussed.     

Effect of Additives on Properties of Lead Titanate

The effect of additives on the properties of lead titanate was investigated. The additives employed were selected on the basis of potential solid solution or liquid formation with PbTiO₃ during sintering. Most of these additives aided sintering and produced dense polycrystalline specimens of PbTiO₃ with densities in the range 89 to 95% of theoretical. The dielectric constant and dissipation factor were found to vary considerably, depending on the additive employed. Some poled specimens exhibited a piezoelectric coefficient, d₃₃, as high as 130 × 10⁻¹² coulombs per newton with a dielectric constant of about 160 at room temperature. The microstructure of some of the specimens was also studied and a texture similar to that of barium titanate was observed for those specimens which gave the higher piezoelectric response.     

组成对锆钛酸铅铁电薄膜电性能影响的研究进展

锆钛酸铅材料因具有优异的介电、压电和铁电性被广泛用于制作电容器、压电器件和铁电随机存储器等功能器件.本文综述了锆钛酸铅铁电薄膜材料中锆钛比、掺杂种类及掺量对其介电性和铁电性的影响,并提出了亟待解决的问题.     

Low-Temperature Synthesis of Nanocrystalline Zinc Titanate Materials with High Specific Surface Area

Nanocrystalline zinc titanate (ZnTiO₃) was synthesized at low temperatures through the combination of a sol–gel processing and a polymer binder method. ZnTiO₃ powders of ∼5 nm in size were obtained by heating pastes, which were composed of a Zn-Ti methanolic solution containing acetylacetone and an organic polymer binder, at 500°C in air. Thermal decomposition behavior of the pastes was analyzed by thermogravimetry-differential thermal analysis. Crystallinity of ZnTiO₃ was examined by transmission electron microscopy. The BET measurement revealed that the powders had a relatively high specific surface area of 106 m²/g.     

Formation of Low-Temperature Seals and Coatings Based on Low-Melting Lead-Tellurite Glasses

The process of formation of seals and coatings based on low-melting lead-tellurite glasses is studied. The results of a microspectral analysis of the element distribution in glass - aluminum and glass - quartz seals are specified. __________ Translated from Steklo i Keramika, No. 6, pp. 40 – 42, June, 2005.     

Investigations of a Diol-based Sol-Gel Process for the Preparation of Lead Titanate Materials

Lead titanate sols were prepared by a sol-gel method from lead acetate trihydrate, Pb(OOCCH₃)₂3H₂O, and titanium di-isopropoxide bis-acetylacetonate, Ti (OC₃H₇)₂- (CH₃COCHCOCH₃)₂, in 1,3-propanediol, HO(CH₂)₃OH, as solvent. IR analysis and NMR spectroscopic techniques were used to study the reaction mechanisms and to identify possible polymer structures developed during synthesis of the solutions.     

Effect of Poling Direction on R-Curve Behavior in Lead Zirconate Titanate

R -curves of lead zirconate titanate (PZT) have been measured with compact tension (CT) specimens for different poling conditions and grain sizes. Depending on poling direction the plateau value of the R -curves ranged from 1.13 to 1.54 MPa·m^1/2 for a grain size of 6.4 μm and from 1.14 to 1.30 MPa·m^1/2 for a grain size of 5.2 μm. Poling in the thickness direction yielded the material with the highest fracture toughness while the direction parallel to the loading direction led to the lowest fracture toughness.     

Low-Temperature Sintering of Lead Zinc Niobate–Lead Zirconate Titanate Ceramics Using Nano-Sized Powder Prepared by the Stirred Media Milling Process

Lead zinc niobate–lead zirconate titanate (PZN–PZT) nano-sized powders with a diameter of ∼35 nm were fabricated by a high-energy stirred media mill using 50 μm diameter zirconia beads as the milling media at a rotation speed of 4000 rpm for 1 h. The sintering temperature of PZN–PZT was greatly reduced, and a fully densified bulk body was obtained at only 750°C when stirred media milled nanopowder was used. The control of evaporation of lead oxide was very important to obtain high electrical properties due to the increased surface area of nano-sized powders. The ferroelectric hysteresis, piezoelectric d ₃₃ coefficient, and dielectric properties of sintered ceramics using nanopowder were measured and compared with the values obtained from a sintered specimen using conventional milled powders. Remanent polarization, d ₃₃ coefficient, and relative dielectric constant of 750°C sintered stirred media milled powders containing 2% of excess PbO and 1% of 4PbO–B₂O₃ liquid phase were 10.3 μC/cm², 277 pC/N, and 1310, respectively.     

Effect of Lead Zirconate Titanate Seeds on PtxPb Formation during the Pyrolysis of Lead Zirconate Titanate Thin Films

Lead zirconate titanate (PZT) thin films were prepared on platinized silicon substrates by dip-coating using a modified diol-based sol–gel route without and with up to 5 mol% PZT nanometric seeds dispersed in the precursor sol. A metastable intermetallic Pt _x Pb phase formed at the early stages of heat treatment. XRD, TEM, and RBS revealed that the thickness and stoichiometry of the Pt _x Pb layer varied with the concentration of seeds and heat treatment of the films. The relation of the Pt _x Pb layer to the final crystalline texture of the PZT thin films is reported and discussed.     

Effect of Lead Zirconate on Positive-Temperature-Coefficient Materials

The addition of small amounts of PbZrO₃ to (Pb,Ba) TiO₃ suitably doped to give positive-temperature-coefficient behavior resulted in a aramatic change in the resistivity-temperature properties of the material. The results are explained on the basis of a synergy between Zr content and Pb volatilization in titanate-based perovskites which favors partial compensation of the Pb vacancies with holes. A secondary result explains the pronounced grain growth which occurs at doping levels where semiconduction begins as being due to a minimum in the vacancy content which results in secondary recrystallization.     

电疲劳对掺镧锆钛酸铅陶瓷电致畴变行为的影响

在不同电疲劳周次下,对未极化掺镧锆钛酸铅铁电陶瓷在不同直流电场加载下得到的原位X射线衍射(XRD)谱和撤掉不同直流电场后得到的非原位XRD谱的(002)与(200)晶面衍射峰强与电场强度(EA)的关系进行研究。通过计算90°畴变体积分数发现,在电疲劳过程中,电场撤掉前后的90°畴变体积分数均随EA呈蝶形曲线变化。在低电场作用下,铁电畴更趋向于沿平行试样表面方向,而在EA=2 000 V/mm作用下,当电疲劳至106时,材料中有约5%的铁电畴被钉扎,有约6%的铁电畴在电场撤掉瞬间转回平行试样表面方向。电场撤掉后的90°畴变体积分数能直接反映铁电材料剩余极化程度。     

Effect of Rare-Earth Additives on Electromechanical Properties of Modified Lead Titanate Ceramics

The influence of rare-earth additives, such as La, Nd, Sm, and Gd, and poling conditions on the electromechanical properties of (Pb_{1−3 x /2}Ln _x )(Ti_0.98Mn_0.02)O₃ compositions, x = 0.04–0.12, were investigated. The type and amount of additive were found to affect the lattice anisotropy, dielectric constant, and electromechanical properties. A large electromechanical anisotropy ( k _t / k _p ) could be obtained in 10 mol% Sm-modified and 8 mol% Gd-modified lead titanate ceramics, and seemed to correlate to a low Poisson's ratio.     

助熔剂法生长的锆钛锡酸铅镧(PLZST)晶体及生长余料的组分分析

以PbO-PbF2复合体作为助熔剂,采有助熔剂自发成核缓冷法率先制备出成分为（Pb0.94La0.04)(Zr0.37Ti0.18Sn0.45)O3的驰豫型复合钙钛矿结构锆钛锡酸铅镧（PLZST）晶体,合适的生长工艺为：助熔剂中PbO与PbF2的摩尔比为0.55:0.45,原料与助熔剂的摩尔比为1：1,保温温度1250℃,保温时间12h,快降温速率为50－100℃／h,慢降温速率为1－5℃/h,快速降温与慢速降温的转变温度为1150℃,本工作对晶体及晶体生长余料中的组分进行了分析,结果表明：对一定组成的初始配料,PLZST晶体组成相对富La,Ti和Zr,生长后的余料相对富Sn,PLZST晶体中存在两种包裹体缺陷,晶体除包裹体以外各元素分布均匀,生长余料中各元素分布较均匀,存在某些元素的相对富集区域。     

含铅低温玻璃釉料表面析铅的研究

以PbO-B2O3-SiO2系统为基础,在PbO质量分数为60%时,对釉料表面析铅问题进行了研究。结果表明,析铅的实质是釉料表面被空气中所含水分侵蚀,Pb2+在釉料中的结构受到破坏,与H2O和CO2发生反应,形成了碱式碳酸铅。     

Impact of Prozonation on the Granulometric Distribution of Materials in Suspension

This study shows the impact of preozonation on the granulometric distribution of materials in suspension. Raw and ozonized waters have been analyzed bya laser granulometer. Analysis of the granulometric distribution of Seine river water has established that the suspended materials are constituted of four Gaussian populations and makes evident the codifications caused by the ozone on this granulometry as well ason the particulate organic carbon.