(NaBi)0.5TiO3基无铅压电陶瓷研究进展

综述了钙钛矿结构（NaBi）0.5TiO3基无铅压电陶瓷的研究现状.评价了（NaBi）0.5TiO3基无铅压电陶瓷的三种改性方法：氧化物掺杂改性、固溶体改性和工艺改性.研究表明：几种方法复合改性效果更佳,无铅压电织构陶瓷压电性能远远优于传统工艺制备的无铅压电陶瓷.     

钙钛矿型织构化无铅压电陶瓷的研究进展

控制陶瓷材料的微观结构,使之在某个方向上择优取向(即织构化)是提高多晶陶瓷介电、压电性能的重要途径之一.基于织构化流程的特点,综述了钙钛矿系无铅压电材料的TGG工艺、种晶的选择与合成方法以及织构化材料的表征技术,提出了无铅压电材料织构化工艺的发展趋势.     

高压电性和织构化无铅压电陶瓷的最新研究进展

近年来,性能优异的无铅压电陶瓷因其环境协调性好、污染小而再度成为研究热点.结合近2年来国内外无铅压电陶瓷的研究现状,主要从陶瓷的制备技术方面综述了目前性能最优的BaTiO3和铌酸盐基织构化无铅压电陶瓷的研究进展.重点介绍了制备压电陶瓷的2种新技术,即工程畴形技术(EDC)和局部化学微晶转化法(TMC).针对现今无铅压电陶瓷的种种不足,对今后压电陶瓷的研究方向作了展望.     

(K,Na)NbO3基无铅压电陶瓷的研究现状与进展

综述了近年来(K,Na)NbO3基无铅压电陶瓷在掺杂改性以及晶粒定向技术制备织构化陶瓷研究的新进展,重点分析了(K,Na)NbO3基无铅压电陶瓷的K/Na比为0.5和非0.5时,陶瓷压电性能上的差异,发现K/Na比偏离0.5时,具有更为优异的压电、介电性能,最后展望了(K,Na)NbO3基无铅压电陶瓷的掺杂改性及晶粒定向技术的研究趋势.     

铌酸钾钠基无铅压电陶瓷的制备和掺杂改性研究进展

结合目前有关铌酸钾钠基无铅压电陶瓷的研究,综述了近年来铌酸钾钠基无铅压电陶瓷在粉体制备、陶瓷的成型、烧结以及陶瓷的织构化特别是反应模板晶粒取向等制备技术上研究的新进展,并比较分析了NNK、NNK-LN、NNK-LT-LS等不同的掺杂改性体系在压电性能上的差异和改进.结果显示,改进后的铌酸钾钠基无铅压电陶瓷致密度高,在压电、介电等性能上均有大幅度的提高,并且出现较宽的准同型相界.最后从不同方面展望了今后铌酸钾钠基无铅压电陶瓷在性能改进上的研究趋势及其制备技术上可能的进展.     

从发明专利看无铅压电陶瓷的研究与发展--无铅压电陶瓷2O年发明专利分析之一

无铅压电陶瓷的研究与开发已引起世界各国的高度重视.本文综合分析了近20年无铅压电陶瓷发明专利约140篇,从发明专利角度评述了无铅压电陶瓷的研究与发展现状,简要介绍了目前受到广泛研究的BaTiO3(BT)基无铅压电陶瓷、Bi1/2Na1/2TiO3(BNT)基无铅压电陶瓷、铋层状结构无铅压电陶瓷及铌酸盐系无铅压电陶瓷,并侧重介绍这些无铅压电陶瓷的组分、性能和制备方法.从无铅压电陶瓷发明专利的进展可以看出,在过去20年中,为促进人类社会的可持续发展,无铅压电陶瓷得到了广泛的研究和开发,并取得重要进展.     

铌酸钾钠基无铅压电陶瓷的制备工艺技术研究进展

基于对人类生存环境的保护和发展环境友好型材料与电子产品的要求,铌酸钾钠(K0.5Na0.5NbO3,简写为KNN)基无铅压电陶瓷由于其具有优越的电学性能和较高的居里温度而成为目前世界范围内压电铁电材料研究的热点之一。材料制备工艺技术在材料科学技术中占有极其重要的地位。结合国际无铅压电陶瓷的研究情况,综述了近年来铌酸钾钠基无铅压电陶瓷在粉体制备、陶瓷烧结以及陶瓷织构化等制备工艺技术上研究的新进展并展望了其发展趋势。     

无铅压电陶瓷纳米粉体的制备及其陶瓷性能研究进展

随着经济的发展和人们环保意识的增强,无铅压电陶瓷的研究和开发越来越引起人们的重视.但此类材料的压电性能相对于铅基压电陶瓷来说还存在较大差距,严重制约着它的实际应用.纳米技术的出现和发展为无铅压电陶瓷性能全面达到或超过铅基压电陶瓷提供了很好的机遇和平台.综述了近年来无铅压电陶瓷纳米粉体的合成方法,比较了纳米粉体和普通原料制备的无铅压电陶瓷的性能,展望了无铅压电陶瓷未来的发展和应用前景.通过调控反应参数,得到不同尺寸和形状的纳米粉体,实现无铅压电陶瓷纳米粉体的尺寸和形状均匀且可控,无铅压电陶瓷的性能必将大幅度地提高.     

从发明专利看无铅压电陶瓷的研究与发展——无铅压电陶瓷20年发明专利分析之一

无铅压电陶瓷的研究与开发已引起世界各国的高度重视。本文综合分析了近20年无铅压电陶瓷发明专利约140篇。从发明专利角度评述了无铅压电陶瓷的研究与发展现状，简要介绍了目前受到广泛研究的BaTiO3(BT)基无铅压电陶瓷、Bi1/2Na1/2TiO3(BNT)基无铅压电陶瓷、铋层状结构无铅压电陶瓷及铌酸盐系无铅压电陶瓷，并侧重介绍这些无铅压电陶瓷的组分、性能和制备方法。从无铅压电陶瓷发明专利的进展可以看出，在过去20年中，为促进人类社会的可持续发展，无铅压电陶瓷得到了广泛的研究和开发，并取得重要进展。     

BNT-BT和BNT-BKT基无铅压电陶瓷研究进展

综述了Bi0.5Na0.5TiO3-BaTiO3系和Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3系无铅压电陶瓷的最新研究进展.总结了各种添加剂对这两种无铅压电陶瓷体系压电性能的影响机理和规律,介绍了当前以各种工艺对其微观结构和压电性能进行改进的研究成果,并展望了这两种无铅压电陶瓷体系的发展趋势.     

织构化工艺在无铅压电陶瓷中的应用

近年来, 织构化工艺作为一种提高无铅陶瓷压电性能的有效方法, 在国内外得到了广泛地研究和关注. 本文综述了几种常用的织构化工艺, 包括热处理技术、非等轴粒子取向固化技术、模板晶粒生长技术、反应模板晶粒生长技术和多层晶粒生长法的发展与应用, 并详细讨论了每一种工艺对陶瓷微结构和织构化生长机制的影响.     

Highly textured bismuth-containing high-temperature superconductor ceramics obtained by uniaxial pressing in liquid medium: Fabrication and properties

A new method of fabricating textured ceramics with a composition of Bi_1.8Pb_0.3Sr_1.9Ca₂Cu₃O_x is described, according to which the initial low-density ceramics is subjected to uniaxial pressing in a liquid medium followed by drying and annealing. Analysis of the X-ray diffraction and scanning electron microscopy data show evidence for a high degree of texture in high-temperature superconductor ceramics fabricated using the proposed method. The results of magnetic measurements indicate that the obtained material possesses anisotropy of the magnetic moment for the magnetic field H oriented parallel and perpendicular to the direction of uniaxial pressing. The textured ceramics also show high diamagnetic response for H parallel to the c axis of grains, which makes these ceramics promising materials for practical applications.     

Magnetically textured ferrofluid in a non-magnetic matrix: Magnetic properties

Texturing of two different magnetic fluids were carried out in paraffin wax under the influence of an external magnetic field. The textured samples were characterized using magnetization measurement and a.c. susceptibility techniques. The results are discussed in the light of ratio of anisotropic energy to magnetic and thermal energies.     

Magnetic properties of textured CoPd nanocrystalline thin films

CoPd is an important nanomaterial for magnetic and magneto-optic storage of information. In this work, CoPd alloyed thin films are grown via radio frequency magnetron sputtering on silicon, glass and polyimide substrates in a vacuum chamber with base pressure of 5 x 10(-8) mbar. The films are nanocrystalline with grain size between 4 and 80 nm. The magnetic properties of thoroughly textured CoPd alloyed thin films are compared to random polycrystalline ones. Magnetization hysteresis loops recorded under fields up to 12 kOe via a home-made magneto-optic Kerr-effect magnetometer reveal strong tendency for perpendicular magnetic anisotropy for the textured film. This anisotropy leads to the formation of well-defined stripe or labyrinthine ferromagnetic domains with the local spins oriented perpendicular to the film plane. The domain patterns and the hysteresis loops are simulated with micromagnetic calculations. Finally, an induced magnetic moment of 0.44 microB/atom is measured for Pd via X-ray magnetic circular dichroism and it is separated into spin and orbital magnetic moment contributions.     

Crystal structure and magnetic properties of Permalloy filmssputtered by mixed Ar-N2 gases

The crystallographic and magnetic properties of 1-μm-thick Permalloy films sputtered by mixed argon and nitrogen gases have been investigated. These films are composed of (111) textured grains of face-centered cubic and (002) textured grains of body-centered tetragonal which are deformed from face-centered cubic. Adding nitrogen to argon gas increases the amount of (002) textured grains and lattice strain. The anisotropy field of these films is smaller than that of films sputtered by pure argon. The coercive force of films containing relatively large amounts of nitrogen increases with annealing. The coercive force of the annealed films is correlated with a change in the lattice constant of the face-centered cubic grains. The magnetocrystalline anisotropy of these grains is likely to be one of the causes of perpendicular anisotropy     

Magnetic and magnetostrictive properties of cube textured nickel for magnetostrictive transducer applications

Magnetic and magnetostrictive properties of {100} <100> textured, polycrystalline nickel sheet have been measured in the <100> direction and compared with a randomly oriented nickel sheet. The {100} <100> textured nickel produced a 51 percent increase in the available magnetostrictive strain energy along with a 21 percent decrease in sound velocity. These improved characteristics when combined with an equivalent electromechanical coupling coefficient and a nearly linear response of magnetostrictive strain to the applied magnetic field, make "cube" textured nickel sheet an attractive new material for many transducer applications.     

On the influence of magnetic field processing on the texture,phase assemblage and properties of low aspect ratio Bi2Sr2CaCu2Ox/AgMg wire

Bi₂Sr₂CaCu₂O_x/AgMg conductors are potentially important for many applications up to 20 K, including magnets for cryogen-free magnetic resonance imaging and high field nuclear magnetic resonance research. One promising approach to increased critical current density is partial-melt processing in the presence of a magnetic field which has been shown to enhance c-axis texturing of wide, thin tape conductors. Here, we report on low aspect ratio rectangular conductors processed in an 8 T magnetic field. The magnetic field is applied during different stages of the heat treatment process. The conductors are electrically characterized using four-point critical current measurements as a function of magnetic field and magnetic field orientation relative to the conductor. The superconductive transition and magnetization hysteresis are measured using a SQUID magnetometer. The microstructures are characterized using scanning electron microscopy and energy dispersive spectroscopy and analyzed using digital image processing. It is found that the presence of a magnetic field during split melt processing enhances the electrical transport and magnetic behavior, but that the anisotropy is not consistently affected. The magnetic field also affects development of interfilamentary Bi2212 bridges, and that this depends on the initial shape of the Bi2212 filament. At least two behaviors are identified; one impacts the oxide phase assemblage and the other impacts textured growth.     

Analysis of experimental conditions for simultaneous measurements of transport and magnetotransport coefficients of high temperature superconductors

Experimental conditions for simultaneous measurements of transport coefficients of high temperature superconductors in zero and non-zero magnetic fields are analysed. Test measurements of the thermal conductivity, the thermoelectric power and the Nernst-Ettingshausen effect of a textured Bi2212 sample are reported in an external magnetic field of 2 T. Errors related to parameters of the thermocouple used and to the spurious heat flows are discussed for a new experimental set-up built based on a closed cycle helium refrigerator. Possible optimising of experimental conditions is suggested.     

On the influence of magnetic field processing on the texture,phase assemblage and properties of low aspect ratio Bi2Sr2CaCu2Ox/AgMg wire

Abstract

Bi₂ Sr₂ CaCu₂ O_x/AgMg conductors are potentially important for many applications up to 20 K, including magnets for cryogen-free magnetic resonance imaging and high field nuclear magnetic resonance research. One promising approach to increased critical current density is partial-melt processing in the presence of a magnetic field which has been shown to enhance c-axis texturing of wide, thin tape conductors. Here, we report on low aspect ratio rectangular conductors processed in an 8 T magnetic field. The magnetic field is applied during different stages of the heat treatment process. The conductors are electrically characterized using four-point critical current measurements as a function of magnetic field and magnetic field orientation relative to the conductor. The superconductive transition and magnetization hysteresis are measured using a SQUID magnetometer. The microstructures are characterized using scanning electron microscopy and energy dispersive spectroscopy and analyzed using digital image processing. It is found that the presence of a magnetic field during split melt processing enhances the electrical transport and magnetic behavior, but that the anisotropy is not consistently affected. The magnetic field also affects development of interfilamentary Bi2212 bridges, and that this depends on the initial shape of the Bi2212 filament. At least two behaviors are identified; one impacts the oxide phase assemblage and the other impacts textured growth.     

Ferromagnetic and spin wave resonances in thin layer of expanded austenite phase

Four samples of austenite coatings deposited by reactive magnetron sputtering on silicon substrate at four different temperatures and pressures were investigated by ferromagnetic resonance (FMR) method at room temperature. The expanded austenite phase S (γ _N ) layers with thickness in the 160–273 nm range and concentration of magnetic atoms: 72 % Fe, 18 % Cr and 10 % Ni, were obtained. The coatings with nanometric size grains were strongly textured and grown mostly in [100] direction, perpendicular to the sample surface. Intense FMR spectra were recorded at various angles between the static magnetic field direction and the sample surface. A strong magnetic anisotropy of the main uniform FMR mode was observed and the effective magnetization 4πM _eff determined. Spin wave resonance (SWR) modes were observed in all investigated samples in out-of-plane geometry of the magnetic field. The resonance fields of SWR modes in our samples varied linearly with the spin wave mode number. The value of the effective magnon stiffness constant was determined assuming a parabolic shape of the magnetization variation across the sample thickness.