Studies of Lead Zirconate Titanate Sol Ageing Part I: Factors Affecting Particle Growth

The formation and growth of polymeric particles during the hydrolysis and condensation of PbZr_0.3Ti_0.7O₃ (PZT 30/70) precursor solutions have been studied as functions of time by using photon correlation spectroscopy (PCS). Particle shape was deduced by measuring the rheological properties of the sols and was found to remain chain-like during sol ageing. Various factors that affect the ageing of PZT sols have been investigated. Ethylene glycol (EG) was found to greatly accelerate the hydrolysis and condensation of the acid-modified Pb-free Zr/Ti solutions but had little effect on the particle growth for the Pb-containing PZT sols. Temperature and H₂O concentration were found to have major effects on the ageing behaviors. The higher the temperature and H₂O concentration, the higher the particle growth rates and the faster the sol gels.     

Determination of Particle Size and Shape during the Hydrolysis of Pb(Zr0.3Ti0.7)O3 Precursor Solutions

The formation and growth of polymeric particles during the hydrolysis and condensation of PbZr_0.3Ti_0.7 O₃ (PZT 30/70) sol-gel precursor solutions have been investigated by using photon correlation spectroscopy (PCS), small angle X-ray scattering (SAXS) and by measuring their rheological properties. The measurements showed that the growth of the particles in the transition of PZT sol to gel followed a simple polymerisation process. Solution A (containing by-products) and Solution B (by-products removed) displayed a similar plot of logarithmic viscosity against logarithmic time, indicating that the particles in both solutions have similar structures after hydrolysis. The changes in viscosity and particle size with time were described by single logarithmic growth models. However, the increasing rate of logarithmic particle size in Solution B is higher than that in Solution A. A model for the form of the aggregates is discussed which is applicable to PZT organometal-particle aggregation process in systems with acetic acid as a modifier.     

Investigation of the Crystallisation Behaviour of Lead Titanate (PT), Lead Zirconate (PZ) and Lead Zirconate Titanate (PZT) by EXAFS-Spectroscopy and X-Ray Diffraction

Two solid solutions of lead zirconium titanates PbZr _x Ti_{1 – x} O₃ (x = 0.1 and 0.35) as well as the reference compounds lead titanate and lead zirconate were prepared from zirconium and titanium n-propoxide, dissolved in 2-methoxyethanol, by sol-gel process. The amorphous products after pyrolysis of the dried gels and the crystalline phases were studied by EXAFS spectroscopy to monitor the structural changes from the amorphous oxide mixture to the crystalline ceramics after calcination. Additionally, the crystalline phases were identified by X-ray diffraction (XRD).It follows from the analysis of the EXAFS data that the local order of the amorphous phases seems to be completely different from that of the crystalline phase. There is no indication of a preformation of the local order of the perovskite structure. The analysis of our EXAFS spectra can be interpreted very consistently with the assumption that in the amorphous samples a segregation exists on molecular level and the low crystallisation temperatures are a consequence of very short diffusion paths.     

Preparation of Lead Zirconate Titanate Ceramic Fibers by Sol-Gel Method

PZT fibers with the nominal composition of Pb(Zr_0.53Ti_0.47)O _x have been successfully drawn by the sol-gel techniques. Ti(O·i–C₃H₇)₄, Zr(O·n–C₄H₉)₄, and Pb(O₂C₈H₁₅)₂ were used as the starting materials. The rheological conditions for continuous gel fiber drawing were determined. Thermal and microstructural evolutions of gel fibers were investigated by X-ray diffraction and Fourier-transform infrared spectroscopy. Perovskite crystalline fibers without breakage were obtained by a two-stage heat treatment on the gel fibers up to 600°C in air. Bending strength of the fibers decreases with the increase of the fiber diameter and is ranged from 10 to 30 MPa.     

Lead Zirconate Titanate Stable Stock Solution: Characterization and Applications

Lead zirconate titanate (PZT) thin films were prepared by the sol-gel process using acetic acid and 1,2-propanediol as solvents. Acetone was used as final solvent and in this way a stable stock sol (for more than 12 months) was obtained. The PZT sols prepared were reproducible and suitable for the preparation of PZT thin films. To study the sol structure evolution gas chromatography mass spectrum (GC-MS) and Fourier-transform-infrared (FT-IR) spectra were recorded and analyzed on each step of the synthesis. The rheological behavior and the stability of the stock sol were checked using a rheometer. It is observed that the addition of acetone leads to a very stable stock sol. The preliminary investigation of the electric properties of the obtained PZT thin films showed that the crystallized films deposited from a fresh prepared sol and a 12 months aged sol exhibit similar ferroelectric properties and comparable to those reported in the literature.     

Heterometallic lead-titanium oxyalkoxide precursors to lead titanate thin films

Two lead titanium oxyalkoxides with composition Pb₂Ti₄O₂(O₂CCH₃)₂(OC₂H₅)₁₄ and Pb₂Ti₂O₂(O₂CCH₃)₂(OCH(CH₃)₂)₈ have been isolated and characterised by elemental analysis, IR, ²⁰⁷Pb NMR and molecular weight measurements. X-ray structural analysis of the 1:2 complex confirmed the presence of two Pb₂Ti₂O units which are linked by a common Pb···Pb edge and are held together by alkoxide and acetate bridges. The acetate groups have migrated from the Pb to the Ti centres during the reaction. Hydrolysis of the 1:1 Pb/Ti complex produced clear gels providing the H₂O/complex ratio was less than 4. Heat treatment of the gel results in loss of residual organics below 400°C. The XRD pattern indicates the presence of the pyrochlore and perovskite phases after heating at 500°C but the sample is poorly crystalline. Complete conversion to the perovskite phase of lead titanate occurs on heating to 600°C for 1 hour. Thin films of lead titanate were deposited by dip-coating a solution of this complex in isopropanol. Analyses of the films, carried out using electron microprobe, Scanning Auger Spectroscopy and Rutherford Backscattering, indicated that they were of excellent quality, crystalline after heating at 600°C and with relatively sharp substrate-coating interface.     

Study by Rutherford Backscattering Spectroscopy of the Heterostructure of Lead Titanate Thin Films

A depth profile analysis of modified lead titanate thin films was performed by means of Rutherford Backscattering Spectroscopy (RBS). These films were deposited from sol-gel synthesized solutions onto platinized silicon substrates and crystallized by thermal treatments at temperatures of about 650°C. The chemistry of the solution and the thermal treatment for crystallization affect the heterostructure of the resulting films. Losses of lead and formation of substrate-film interfaces are produced during the crystallization of the films. These film characteristics determine their ferroelectric response.     

过氧化合物法PLZT纳米粉体的制备和表征

掺镧的锆钛酸铅固溶体（Pb1-x,Lax）(Zry,Ti-y)1-x/4O3（简称PLZT）是一种有重要用途、性能优良的电光陶瓷材料[1]。为避免局部组成变化引起散射和保证良好的电光性能,材料的组成和均匀性非常重要。用传统的固相法制备PLZT粉体耗能大,生成的粉体颗粒大,组成均匀性差,不能满足现代高科技应用的要求。近年来研究的溶胶．凝胶[2]、柠檬酸法[3]、EDTA凝胶法[4]等湿化学法有许多优点,受到人们的关注,但这些方法需用较贵原料。而在众多的湿化学法中,以共沉淀法最为经济,并且它比传统的固相法好,能够制得均匀性好的纳米粉体。但该…     

A novel route to perovskite lead zirconate titanate from glycolate precursors via the sol–gel process

A perovskite lead zirconate titanate was synthesized by the sol‐gel process, using lead glycolate, sodium tris(glycozirconate) and titanium glycolate as the starting precursors. For the mole ratio Pb:Zr:Ti of 1:0.5:0.5 [Pb(Zr_0.5Ti_0.5)O₃], TGA‐DSC thermal analysis indicated that the percentage of ceramic yield was 55.8, close to the calculated chemical composition value of 49.5. The exothermic peak occurred at 268 °C below the theoretical Curie temperature of 400 °C. The pyrolysis of Pb(Zr_0.5Ti_0.5)O₃ of the perovskite phase was investigated in terms of calcination temperature and time. The structure obtained was of the tetragonal form when calcined at temperatures below 400 °C; it transformed to the tetragonal and the cubic forms of the perovskite phase on calcination above the Curie temperature, as verified by X‐ray data. The lead zirconate titanate synthesized and calcined at 400 °C for 1 h had the highest dielectric constant, the highest electrical conductivity and the dielectric loss tangent of 10 190, 0.803 × 10^?3 (Ω.m)^?1 and 1.513 at 1000 Hz, respectively. The lead zirconate titanate powder synthesized has potential applications as an electronic material. Copyright © 2008 John Wiley & Sons, Ltd.     

纤维钛酸铅/纳米钛酸铅晶体复合陶瓷材料性能研究

钛酸铅（PbTiO3）在常温下属于典型的钙钛矿结构,其居里温度高达490℃,介电常数小,压电性能高,压电各向异性大,是一种优良的高温高频的压电材料,但因其轴向比c/a=1.063和矫顽场大,难于极化,在冷却过程四方至立方的相变中易出现微细裂纹,有时甚至破碎,所以制备纯相致密的PbTiO3陶瓷存在烧结上的困难,且因陶瓷本身固有的脆性,使其优良的电性能很难得到充分的开发和利用。PbTiO3的应用通常是通过掺杂改性而获得的。而掺杂改性会对其电性能产生不良的影响。如能寻找一种有效的方法,即改善其烧结特性,又不影响其电性能,而且能制得致密的PbTiO3陶瓷,则对PbTiO3的研究与应用具有重要的意义。     

Ca改性钛酸铅纳米晶的制备及结构研究

用溶胶-凝胶工艺制备了Pb_1-xCa_xTiO₃(0≤x≤0.3)纳米晶,在不同焙烧条件下研究其粉体晶相结构的变化.研究结果表明,升温速度和焙烧温度对纳米粉的晶相、晶胞参数和晶粒尺寸有显著影响.讨论了晶胞参数、四方畸变度和晶胞体积与Ca含量的关系.     

Ferroelectric Properties of Modified Lead Titanate Thin Films Obtained by a Sol-Gel Method

Calcium substituted lead titanate thin films have been prepared by a sol-gel method, deposited by spin-coating, and thermally treated so as to obtain a perovskite structure. Two types of thermal treatments were given, differing in the heating rate, which in conventional treatments was of some 10°C/min, and in rapid treatments >500°C/min. With rapid heating, materials are obtained in which greater polarizations are commuted and bias fields are smaller. This, together with the fact that additional (undesired) phases are not observed by X-ray diffractometry when rapid treatments are used, shows that these are to be preferred over conventional treatments.     

双硫腙包覆钛酸锶钡粉体对水中铅的吸附行为

用草酸化学共沉淀法合成了钛酸锶钡(BST)粉体, 以双硫腙为表面修饰剂, 采用静态浸渍法对钛酸锶钡粉体进行表面包覆修饰, 制备出新型固态粉体吸附剂. 利用X射线衍射(XRD)、扫描电镜(SEM)和傅立叶变换红外光谱(FTIR)进行了表征. 研究了该吸附剂对水中铅的吸附行为. 结果表明: 双硫腙通过与钛酸锶钡表面羟基形成氢键作用包覆于该粉体上; 当吸附介质pH值大于4时, 该吸附剂对水中的铅有较强的吸附能力; 室温下, 5 min内吸附达到平衡. 其吸附行为符合Langmuir吸附等温模型和HO准二级动力学方程式, 吸附焓变(ΔH)为19.42 kJ•mol^－1, 活化能(E_a)为22.187 kJ•mol^－1, 该吸附过程是吸热的物理过程. 吸附在双硫腙包覆钛酸锶钡粉体上的铅, 可用1 mol•L^－1的硝酸溶液进行洗脱. 建立了吸附富集、火焰原子吸收法测定水中铅的新方法, 应用于地表水和自来水中铅的测定, 取得了令人满意的结果.     

Hydrothermal Synthesis and Phase‐, Morphology‐Evolution Mechanism of Lead Titanate Nanostructures Assisted with Tetramethylammonium Hydroxide

Lead titanate nanostructures with different phases and morphologies, layered hexagonal PbTiO₂(CO₃)_0.3‐ (NO₃)_0.35(OH) nanosheets, pyrochlore Pb₂Ti₂O₆ nanodendites, pre‐perovskite PbTiO₃ nanofibres and perovskite PbTiO₃ nanoplates, have been synthesized via a conventional hydrothermal route assisted with different concentrations of tetramethylammonium hydroxide (TMAH). X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high‐resolution TEM (HRTEM) were employed to characterize the phase, morphology and growth behavior of the synthesized samples. The results reveal that at low TMAH concentration the obtained samples are mainly of PbTiO₂(CO₃)_0.3(NO₃)_0.35(OH) nanosheets. With the TMAH concentration increasing, the obtained samples change to pyrochlore Pb₂Ti₂O₆ nanodendites, pre‐perovskite PbTiO₃ nanofibres and perovskite PbTiO₃ nanoplates in turn. With the basis of the experimental results, the phase‐ and morphology‐evolution mechanism of the lead titanate nanostructures is discussed by combining the analysis of the lattice structure feature and the properties of TMAH.     

Effect of post-metallization annealing on the ferroelectric properties of sol-gel derived PZT thin films

A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model.     

Characterization of Particle Size and Shape in an Ageing Bismuth Titanate Sol Using Dynamic and Static Light Scattering

The ageing characteristics of a metal-alkoxide solution, used to prepare thin films of ferroelectric bismuth titanate, Bi₄Ti₃O₁₂, were carefully scrutinized using laser light scattering. Dynamic light scattering experiments revealed a bimodal distribution of hydrodynamic diameters, with larger molecular clusters increasing in size from 4 to 68 nm over the course of 60 days ageing in a sealed vial. Static light scattering measured the radius of gyration to be 71 nm. Comparison of these two results suggests that these clusters are approximated as thin cylindrical (or chainlike) structures. Using ellipsoid scattering theory, plots of scattered light intensity versus q (scattering) vector also suggest a long cylindrical type cluster with a length of 350 nm and a diameter of 4 nm. Some deviation of experimental data from the theoretical curves probably is an indication of some flexibility and/or fractal nature of the molecular clusters. Such anisotropy in oligomeric cluster shape apparently has a strong influence on final crystallographic texturing of ceramic thin films made by spin-coating of these solutions on flat substrates.     

聚氨酯与铁电陶瓷粉复合物的电致感应性能研究

利用双辊制备了一系列热塑性弹性体聚氨酯（PU）和铁电钛酸锆酸铅盐（PZT）的电感应PZT／PU复合物。X－衍射和SE镜结果显示,复合物中,在铁电相中PZT陶瓷粉呈现结晶态并且均匀分布在PU基体中,复合物的弹性模量和相对电容率随着复合物中PZT体积分数增加而升高,在高压电场下,低PZT含量的复合物呈现负的电致伸缩应力,当PZT体积分数增加到6％以上时,在某个临界电场下,复合物呈现出电致伸缩应力反转的特性,即电致伸缩应力从负转变为正,并且发生应力反转的临界电场随着复合物中PZT体积分数的增加而降低,PU的电致伸缩特性与PZT在高电场下极化反转效应结合,导致了PZT／PU复合物这种有趣的性能,因此PZT／PU复合物将在高电压场方面作为传感器开关材料得到广泛应用。     

Preparation of Barium Titanate and Related Materials by the Alkoxide-Hydroxide Route

Formation of perovskites MTiO₃ (M = Ba, Sr) at low temperature (< 100°C) by heterogeneous reactions of M(OH)₂ aqueous solutions with hydrolysis products of Ti(OBu)₄ is discussed. Reaction products are characterized by means of chemical and X-ray analysis, and electron microscopy. Reaction rate is enhanced by hydroxide concentration and reaction temperature, and increases drastically when Sr(OH)₂ is used instead of Ba(OH)₂. Particles shape and size of the perovskites formed is independent of morphology of Ti(OBu)₄ hydrolysis product. The main factor of perovskites morphology regulation lies in the rate of M(OH)₂ absorption. Lowering the absorption rate allows us to prepare uniform perovskite powders which can be readily sintered to ceramic bodies with high dielectric permittivity.     

A novel route to perovskite lead zirconate from lead glycolate and sodium tris(glycozirconate) via the sol–gel process

A perovskite lead zirconate was synthesized, using lead glycolate and sodium tris (glycozirconate) as the starting precursors, by the sol–gel process. The obtained molar ratio Pb:Zr of PbZrO₃ was 0.9805:1. The TGA–DSC characterizations indicated that the percentage of ceramic yield was 56.4, close to the calculated chemical composition of 59.6. The exothermic peak occurred at 245.7 °C, close to the theoretical Curie temperature of 230 °C. The pyrolysis of PbZrO₃ of the perovskite phase was investigated in terms of calcination temperature and time. The structure obtained was the orthorhombic form when calcined at low temperature at 300 °C for 1 h; it transformed to the monoclinic and cubic forms of the perovskite phase at higher temperatures above the Curie temperature as verified by X‐ray data. The lead zirconate synthesized and calcined at 300 °C for 1 h has the highest dielectric constant, the highest electrical conductivity and the dielectric loss tangent of 2267, 3.058 × 10^?4 (Ω m)^?1 and 2.484 at 1000 Hz, respectively. The lead zirconate powder produced has potential applications as materials used in microelectronics and microelectromechanical systems. Copyright © 2007 John Wiley & Sons, Ltd.     

Sol-Gel Synthesis of Nano-Scaled BaTiO3, BaZrO3 and BaTi0.5Zr0.5O3 Oxides via Single-Source Alkoxide Precursors and Semi-Alkoxide Routes

Sol-gel synthesis of nano-sized BaTiO₃, BaZrO₃ and BaTi_0.5Zr_0.5O₃ ceramics using alkoxide and semi-alkoxide routes has been investigated and the pervoskites obtained have been compared with respect to crystallisation temperature, crystallite size and compositional purity. Heterometal alkoxides containing two (for BaTiO₃ and BaZrO₃) and three (for BaTi_0.5Zr_0.5O₃) different metals were used as single-source precursors in the alkoxide route while semi-alkoxide synthesis was performed by reacting barium hydroxide or acetate with Ti and/or Zr alkoxides. Semi-alkoxide synthesis also produces stoichiometric and phase-pure oxides, however, at temperatures higher than 1000°C. At temperatures below 1000°C, BaCO₃ and small amounts of other undesired phases (e.g., BaTi₂O₄) were present in the oxides derived from semi-alkoxide synthesis. Thermal behaviour, studied by TGA/DTA measurements, shows that thermal decomposition occurs in three major steps and depends on the educt composition and the synthesis route. Among alkoxide derived powders, crystalline BaTi_0.5Zr_0.5O₃ phase is formed at 400°C while complete crystallisation of BaMO₃ ceramics occurs around 600°C. The cubic to tetragonal phase transition for BaTiO₃ is clearly observed at relatively low-temperature of 800°C. The stoichiometry and phase homogeneity of the obtained powders were demonstrated by energy dispersive X-ray analysis and powder diffractometry. The averaged crystallite size of the obtained nano-ceramics was evaluated using the FormFit programme. SEM and TEM observations revealed a high microstructural uniformity.