共查询到20条相似文献,搜索用时 15 毫秒
1.
Malgorzata M. Lencka rzej Anderko Richard E. Riman 《Journal of the American Ceramic Society》1995,78(10):2609-2618
A previously developed thermodynamic model of hydro-thermal synthesis of ceramic powders has been extended to include cases when solid solutions are formed. The model has been applied to the synthesis of a series of lead titanate zirconate solid solutions PbZr x Ti1– x O3 (PZT, 0.46 < x ≤ 0.75). It predicts the optimum conditions (i.e., reagent, concentration, pH, and temperature) for the precipitation of phase-pure homogeneous PZT, provided that the reactants are well mixed. The predictions have been experimentally corroborated using coprecipitated hydrous oxide Zr x Ti1– x C2 n H2 O (0.46 < x ≤ 0.75), as a precursor for Ti and Zr and water-soluble lead acetate or nitrate salts as a source for Pb. When mixtures of hydrous oxides ZrO2 · n H2 O and TiO2 · n H2 O were employed as Ti and Zr precursors, independent PbTiO3 and PbZrO3 precipitates rather than the PZT solid solutions formed. These results can be rationalized on the basis of reaction kinetics where thermodynamic modeling includes or excludes the possibility of solid-solution formation. 相似文献
2.
A thermodynamic model has been developed to determine the reaction conditions favoring low temperature direct synthesis of barium titanate (BaTiO3). The method utilizes standard-state thermodynamic data for solid and aqueous species and a Debye-Hǔckel coefficients model to represent solution nonideality. The method has been used to generate phase stability diagrams that indicate the ranges of pH and reagent concentrations, for which various species predominate in the system at a given temperature. Also, yield diagrams have been constructed that indicate the concentration, pH and temperature conditions for which different yields of crystalline BaTiO3 can be obtained. The stability and yield diagrams have been used to predict the optimum synthesis conditions (e.g.,reagent concentrations, pH and temperature). Subsequently, these predictions have been experimentally verified.As a result, phase-pure perovskite BaTiO3 has been obtained at temperature ranging from 55 to 85℃ using BaCl2,TiCl4 as a source for Ba and Ti. and NaOH as a orecioitator. 相似文献
3.
Bongsoo Kim Seungbum Hong Gun Ahn Kwangsoo No 《Journal of the American Ceramic Society》2016,99(7):2221-2225
Here, we demonstrate a novel process to convert TiO2 nanotubes into ferroelectric nanohoneycombs, comprised of vertically aligned PbTiO3 nanotubes. Tube bottom opening process enabled effective infiltration of lead acetate precursor into the nanotubes. Nanohoneycombs, which were converted via additional lead supplement process, showed uniform conversion and well‐defined ferroelectric properties with the effective piezoelectric coefficient of approximately 20 pm/V, which was measured by piezoresponse force microscopy. 相似文献
4.
Humin Cheng Jiming Ma Zhenguo Zhao Di Qiang Yongxiang Li Xi Yao 《Journal of the American Ceramic Society》1992,75(5):1123-1128
A pure, acicular lead titanate (PbTiO3 ) fine powder with a white color has been prepared by hydrothermal synthesis. It is a new phase of PbTiO3 with I 4 symmetry, cell parameters of a = 12.358 Å and b = 14.541 Å, and a density of 6.80 g.cm−3 . The influences of pH (12.5 to 14.4), Pb/Ti ratio (1.0 to 1.6) in the feedstock, reaction temperature (130° to 230°C), time (0.25 to 4 h), starting materials, and additives on the formation of acicular PbTiO3 under hydrothermal conditions have been investigated. The acicular PbTiO3 with I 4 symmetry, referred to as the PX phase, can be converted to the perovskite-type (PE phase) of PbTiO3 at about 605°C while its acicular morphology is essentially unchanged. The preferable conditions for preparing pure acicular PX-phase PbTiO3 are that the pH is 13.0 to 14.0, Pb/Ti ratio is >1.3, reaction temperature is 170° to 200°C, time is 0.5 to 1.0 h, titanium butoxide (Ti[O(CH2 )3 CH3 ]4 ) is the starting material, and poly(vinyl alcohol) is an additive. The acicular grain of the PX phase is usually less than 100 nm in diameter and more than 1000 nm in length. 相似文献
5.
George A. Rossett Jr. K. R. Udayakumar Michael J. Haun L. Eric Cross 《Journal of the American Ceramic Society》1990,73(11):3334-3338
A phenomenological free-energy function including the effects of elastic boundary conditions was presented and used to investigate the single-domain, single-crystal properties of the ferroelectric perovskite, PbTiO3 . In particular, the effects of tensile and compressive hydrostatic stress on the spontaneous polarization, Curie point, dielectric susceptibility, and piezoelectric property coefficients were examined. The calculated shift of the Curie point with hydrostatic stress, along with the entropy and enthalpy of the ferroelectric-paraelectric phase transition, was found to be in good agreement with experimental measurements. The isothermal variation of the relative dielectric susceptibility and piezoelectric coefficients with hydrostatic stress exhibited the expected behavior near the ferroelectric-paraelectric phase transition. 相似文献
6.
Shin-ichi Hirano Toshinobu Yogo Koichi Kikuta Yasushi Araki Masahiro Saitoh Satoru Ogasahara 《Journal of the American Ceramic Society》1992,75(10):2785-2789
Crack-free Pb(Zr,Ti)O3 (PZT) thin films with preferred orientation were prepared successfully on MgO (100), SrTiO3 (100), and Pt/Ti/SiO2 /Si substrates from metal alkoxide solutions. Calcination of precursor films in a H2 O─-O2 gas mixture was found to be effective not only for low-temperature crystallization of perovskite PZT, but also for obtaining the preferred orientation of PZT films. Single-phase PZT films with high preferred orientation were synthesized on MgO (100) and Pt/Ti/SiO2 /Si substrates at 550° and 600°C for 2 h, respectively. The PZT film on the Pt/Ti/SiO2 /Si substrate showed a permittivity of 520, tan δ of 0.03, a remanent polarization of 24 μC/cm2 , and a coercive field of 54 kV/cm. 相似文献
7.
Junmin Xue Dongmei Wan See-Ee Lee John Wang 《Journal of the American Ceramic Society》1999,82(7):1687-1692
High-density lead zirconate titanate (PZT) ceramics have been successfully prepared by using a novel mechanochemical fabrication technique, which skips the phase-forming calcination at an intermediate temperature that is always required in the industrial processes currently in use. The fabrication technique starts with mixing of the low-cost industrial oxide powders, and the designed PZT perovskite phase is formed by reacting the oxide constituents in a mechanochemical chamber that consists of a cylindrical alumina vial and one stainless-steel ball inside it. The solid-state reaction among constituent oxides is activated via mechanical energy instead of high temperature. When mechanochemically activated for 20 h, an ultrafine PZT powder of perovskite structure with a minimized degree of particle agglomeration is obtained. The resulting PZT powder sinters to 99.0% of theoretical density at 1100°C for 1 h. The sintered PZT ceramic exhibits a dielectric constant of 1340 and a dielectric loss of 0.6% at a frequency of 1 kHz at room temperature. 相似文献
8.
Edson R. Leite Elaine C. Paris Elson Longo Francesco Lanciotti Jr. Carlos E. M. Campos Paulo S. Pizani Valmor Mastellaro Carlos A. Paskocimas Jose Arana Varela 《Journal of the American Ceramic Society》2002,85(9):2166-2170
The crystallization process of lead titanate (PT) prepared using the polymeric precursor method was investigated using X-ray diffractometry, Raman spectroscopy, electron microscopy, and X-ray absorption spectroscopy techniques. The results showed that amorphous PT was formed by an O–Ti–O structure composed of fivefold and sixfold oxygen-coordinated titanium. The local structure of the amorphous PT phase was similar to that of the cubic PT phase, i.e., similar coordination number and similar bond lengths, leading to a topotactic-like transformation during the phase transformation from amorphous to cubic perovskite PT. Because of the low crystallization temperature, every transformation observed during the crystallization process was associated with a short-range rearrangement process. 相似文献
9.
Microwave Effects in Lead Zirconium Titanate Synthesis: Enhanced Kinetics and Changed Mechanisms 总被引:5,自引:0,他引:5
Balasubramaniam Vaidhyanathan Anirudh P. Singh Dinesh K. Agrawal Thomas R. Shrout Rustum Roy Suman Ganguly 《Journal of the American Ceramic Society》2001,84(6):1197-1202
A novel, simple, and fast solid-state procedure has been demonstrated for the synthesis of Pb(Zr,Ti)O3 (PZT), using microwave radiation. The process consists of starting with the respective oxides mixed in the required proportions and exposing the charge to the microwaves. By making one or more of the constituent oxides slightly nonstoichiometric, enormous enhancement in reaction rates has been achieved, and single-phase PZT can be synthesized at temperatures as low as 600°C. Moreover, it has been shown that the combined use of nonstoichiometric precursors and microwave irradiation leads to different reaction pathways for the formation of PZT. Further, the microwave method diminishes PbO loss. 相似文献
10.
Nanocrystalline Lead Titanate and Lead Titanate/Vinylidene Fluoride-Trifluoroethylene 0-3 Nanocomposites 总被引:1,自引:0,他引:1
Yan Chen Helen L. W. Chan Chung Loong Choy 《Journal of the American Ceramic Society》1998,81(5):1231-1236
Lead titanate (PT) powders of nanometer particle sizes were prepared using a sol-gel process. The PT gel was annealed at various temperatures to produce powders with different particle sizes. X-ray diffractometry (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) revealed that the PT gel initially crystallized at an annealing temperature of 500°C. The crystallite diameter measured by XRD increased from 27 to 54 nm, while the size of PT particles increased from 30 to 270 nm as the annealing temperature increased from 500° to 900°C. Lead titanate/vinylidene fluoride-trifluoroethylene (PT/P(VDF-TrFE)) 0-3 nanocomposites with PT volume fractions of 0.18 and 0.41 were prepared using PT powders annealed at various temperatures. Because the pyroelectric coefficients of the ceramic and polymer phases had like signs and the piezoelectric coefficients had opposite signs, the poled composite had high pyroelectric but very low piezoelectric activity, thereby reducing vibration-induced electrical noise in pyroelectric sensor applications. 相似文献
11.
The present research describes synthesis of perovskite lead zirconate titanate (PZT) nanocrystalline mesoporous powders from the aqueous solutions of Pb2+ , Zr4+ , and Ti4+ metal ions using sucrose as a template material. Sucrose retains the metal ions in solution through complex formation. Dehydration and thermal decomposition of the metal ion–sucrose mass produces a large amount of gas, which helps to create porosity and high surface area in the final products. The particle size of the synthesized powder is between 50 and 60 nm, with a average specific surface area between 20 and 25 m2 /g. The surface area increases as the amount of sucrose increases. Nanocrystalline PZT powder with high surface area can be useful for low-temperature sintering. 相似文献
12.
Low-Temperature Preparation of Nanocrystalline Lead Zirconate Titanate and Lead Lanthanum Zirconate Titanate Powders Using Triethanolamine 总被引:2,自引:0,他引:2
Rabindra N. Das Amita Pathak Panchanan Pramanik 《Journal of the American Ceramic Society》1998,81(12):3357-3360
Nanocrystalline lead zirconate titanate (PZT) powders, with a Zr:Ti ratio of 60:40, have been prepared from a solution of triethanolamine (TEA) and Ti4+ , Zr4+ , and Pb2+ ions. The metal ions were in solution through complex formation with TEA. The soluble metal-ion–TEA complex formed the precursor material when it was completely dehydrated. Heat treatment of the precursor at 450°C resulted in single-phase PZT powders. The precursor and the heat-treated powders have been characterized by using thermal analysis and X-ray diffractometry (XRD) studies. The average particle size, as measured from X-ray line broadening and transmission electron microscopy studies, was ∼20 nm. PZT powders modified with 3 mol% of lanthanum (PLZT) also were prepared through this route and were investigated via XRD studies. The dielectric constants of the PZT and PLZT powders were 12475 and 11262, and their corresponding Curie temperatures were 362° and 315°C, respectively. 相似文献
13.
The eutectic and solidus temperatures of the PbTiO3 -KF binary system were investigated by DTA for four compositions. Optical studies of crystal habit as a function of crystallization conditions were used to determine favorable conditions for growing PbTiO3 crystals from a KF flux. Results of X-ray studies of these crystals agree closely with those of earlier studies. Interferometric measurements of thermal expansion confirmed the ferroelectric transition at 490° C. Specific heat studies indicated a transition energy of about 1550 cal/mole with an entropy change of 2.055 cal/mole °C. Spontaneous polarization was calculated as 66 μcoulombs/cm2 . 相似文献
14.
Gilles Robert Marlyse Demartin Maeder Dragan Damjanovic Nava Setter 《Journal of the American Ceramic Society》2001,84(12):2869-2872
A modified processing method for lead nickel niobate–lead zirconate titanate (Pb(Ni1/3 Nb2/3 )O3 –Pb(Zr,Ti)O3 , PNN–PZT) solid solutions is presented. This method is based on the high-temperature synthesis of a precursor that contains all the B-site cations (Ti, Zr, Ni, and Nb). This synthesis yields a diphasic mixture that contains a ZrTiO4 -like phase and a rutile-like phase. Both phases exhibit a cationic valence of 4; thus, it is concluded that the mixing of Ni and Nb cations is adequate for the preparation of PNN–PZT solid solutions. Indeed, a pure perovskite phase has been obtained after calcination with lead oxide for compositions that contain 40 and 50 mol% PNN. Moreover, their electromechanical properties have been shown to be superior to values reported for standard columbite routes. This conclusion has been interpreted in terms of enhanced chemical homogeneity. 相似文献
15.
16.
Synthesis of Lead Zirconate Titanate Stannate Antiferroelectric Thick Films by Sol-Gel Processing 总被引:1,自引:0,他引:1
Baomin Xu L. Eric Cross Duraiswamy Ravichandran 《Journal of the American Ceramic Society》1999,82(2):306-312
The effects of different sintering procedures on the preparation of antiferroelectric thick films and the structure–property relations in these films were studied. An acetic acid-based sol–gel processing with multistep annealing and suitable lead oxide overcoat layers was developed to fabricate both niobium-doped and lanthanum-doped lead zirconate titanate stannate antiferroelectric thick films. The 5-μm-thick Pb0.99 Nb0.02 (Zr0.85 Sn0.13 Ti0.02 )0.98 O3 films demonstrate typical square hysteresis loops with a maximum polarization of 40 μC/cm2 , zero remanent polarization, an antiferroelectric-to-ferroelectric phase transition field of 153 kV/cm, and a ferroelectric-to-antiferroelectric phase transition field of 97 kV/cm. The dielectric constant and dielectric loss are 283 and 1.7%, respectively. The 5-μm-thick Pb0.97 La0.02 (Zr0.65 Sn0.31 Ti0.04 )O3 films display typical slanted hysteresis loops with very small hysteresis, a maximum polarization of 35.0 μC/cm2 , and zero remanent polarization. The dielectric constant and dielectric loss are 434 and 2.0%, respectively. 相似文献
17.
Thierry Delahaye Ali Al‐Zein Marie‐Hélène Berger Xavier Bril Jean‐François Hochepied 《Journal of the American Ceramic Society》2014,97(5):1456-1464
Potassium niobate–lead titanate solid‐solution nanoparticles have been synthesized using a new hydrothermal method. The key step is an in situ acid–base exothermic reaction with a large excess of KOH, generating an amorphous precipitated gel. This gel, when crystallized in an autoclave for 2 h at 190°C, produces a mixed perovskite solid solution with [KNbO3]0.8–[PbTiO3]0.2 (KNPT) composition, and parallelepiped particles rang in size from a few tens to a few hundreds of nanometer in length. This study proves that the pure perovskite phase can be obtained in spite of the different solubilities of the reactive cations in an ethanol–water solution. Dielectric measurements show that KNPT ceramic with a grain size of 50 nm is ferroelectric at room temperature. In addition, ceramics sintered at 950°C have an average grain size of 500 nm, and exhibit a maximum permittivity of 2100 at 1 kHz near TC = 510 K and a remanent polarization Pr = 12 μC/cm2 相似文献
18.
锆钛酸铅(PZT)粉体合成的研究进展 总被引:1,自引:0,他引:1
锆钛酸铅(PbZrxTi1-xO3,PZT)陶瓷是一类重要的铁电、压电、介电材料,其粉体的相组成、化学组成、热稳定性和烧结活性影响着陶瓷制品的铁电、压电和介电性能。本文详细综述了合成PZT粉体的固相反应法和湿化学方法的发展现状,并对几种合成方法的特点进行了评介,为低温合成纯相PZT粉体和PZT一维纳米结构指出了可能的方法。 相似文献
19.
Peer Löbmann Walther Glaubitt Jochen Fricke 《Journal of the American Ceramic Society》1997,80(10):2658-2666
Crack-free monolithic lead titanate (PbTiO3 , or PT) aerogels were prepared via a sol-gel process and drying in supercritical carbon dioxide. The material was characterized by thermogravimetric analysis, dilatometry, helium pycnometry, and X-ray diffraction. Skeletal densification was the main reason for the observed shrinkage of the heat-treated porous material at temperatures <450°C. The transition (at temperatures of 500°-600°C) from an amorphous state to the crystalline (tetragonal) PT was accompanied by significant particle coarsening, as revealed by transmission electron microscopy. Nitrogen adsorption measurements confirmed that crystallization was preceded by the formation of interparticle necks. 相似文献
20.
Vaporization of Lead Zirconate-Lead Titanate Materials 总被引:2,自引:0,他引:2
DAVID A. NORTHROP 《Journal of the American Ceramic Society》1967,50(9):441-445
A thermogravimetric investigation of the vaporization of cold-pressed Pb(Zr0.65 Ti0.35 )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. 相似文献