铁酸镧掺杂对铌酸钾钠基陶瓷介电和铁电性能的影响(英文)

用传统固相反应法制备了(K0.5Na0.5)NbO3(KNN)和0.98(K0.5Na0.5)NbO3-0.02LaFeO3(0.98KNN-0.02LF)无铅陶瓷,并对其介电、铁电性质以及相结构进行了研究.KNN陶瓷是正交相,0.98KNN-0.02LF陶瓷是伪立方相结构.介电研究表明:0.98KNN-0.02LF陶瓷的介温曲线与KNN陶瓷相比较出现两点异常:(i)正交相–四方相相变温度(TO-T)和四方相–立方相相变温度(TT-C)均降低;(ii)最高介电常数温度Tm附近的相变温度宽化.并且,0.98KNN-0.02LF陶瓷在0～400℃内显示了相对比较平坦的介电常数,介电常数达到2000,介电损耗低于4%.电滞回线变"窄"进一步证明了0.98KNN-0.02LF陶瓷的弛豫性.     

二氧化钒薄膜材料相变临界场强调控方法研究

采用无机溶胶-凝胶法并结合真空退火工艺在Al_2O_3陶瓷基片上制备了二氧化钒及其他价态钒氧化物共存的薄膜材料。研究了退火时间对VO_2、V_2O_5、V_6O_(13)、V_6O_(11)等价态成分和含量的影响以及对薄膜的相变临界温度和相变临界电场强度的影响。实验采用的退火时间分别为10h、8h及6h,得到的薄膜的相变临界电场强度分别为1.8 MV/m、0.8 MV/m及0.4 MV/m,相变场强降低75%以上,且随着电场强度相变点的降低,薄膜材料相变点前后电阻变化倍数也降低,但相变临界温度没有明显变化。研究结果表明:通过控制真空退火时间能够实现对电场强度相变点的有效调控,利用该方法可以研制不同相变临界场强的薄膜材料,以适应不同电磁环境的防护应用要求。     

PMN-BT陶瓷的介电性能和相变温度

制备了一系列PMN－BT陶瓷,系统地研究了BT含量的变化对介电性能和相变温度的影响。PMN－BT陶瓷的相变温度与组成吴“U”型变化曲线,相变温度的异常化是由于系统中存在Ba(Mg1/3Nb2/3)O3顺电微区所致。PMN－BT陶瓷的介电驰豫特性随BT的增加经历了一个由弱变强,再由强变弱的过程,对由两种钙钛矿化合物构成的铁电固溶体相变温度的变化规律进行了讨论。     

陶瓷(V_(1-x)Cr_x)_2O_3系统中金属—绝缘体相变的X射线衍射研究

本文讨论在常温和29～207℃温区内用 X 射线衍射技术研究(V_(1-x)Cr_x)_2O_3陶瓷样品中的金属—绝缘体(M—I)相变。实验中发现,即使在低于相变点的室温下,样品中仍存在部分绝缘相。同时发现金属—绝缘体相变温区很宽。作者对此进行了分析讨论,认为导致上述现象的直接原因是材料的成分起伏和应力起伏。对M—I 相变的过程提出了假设模型,并在此基础上解释了陶瓷样品的 X 射线实验结果和阻温特性。     

BCZT无铅压电陶瓷的铁电相变

根据升温拉曼光谱和电学性能的变化研究了(Ba_(0.84)Ca_(0.15)Sr_(0.01))(Ti_(0.90)Zr_(0.09)Sn_(0.01))O_3(BCSTZS)陶瓷的铁电相变。BCSTZS陶瓷的拉曼模分为v_3(LO),v_3(TO),v_4(LO),v_2(LO,TO),v_1(TO)和v_1(LO)模。v_3(LO)和v_4(LO)模在升温至80℃后消失,表明BCSTZS的相结构从四方铁电相转变为立方顺电相。v_3(TO),v_2(LO,TO),v_1(TO)和v_1(LO)拉曼模的峰强和峰宽在室温和80℃附近出现明显的异常变化,表明在这两个温度点附近分别发生正交-四方和四方-立方铁电相变。BCSTZS陶瓷在高于居里温度(TC)时仍然存在拉曼峰,表明其内部存在极性微区。随着温度的升高谐振频率(f_r)和反谐振频率(f_a)互相接近,f_a在TC附近出现不连续变化,而应变和逆压电系数 d_(33)*( d_(33)*=S_(max)/E_(max))值随着温度的升高而逐渐降低,进一步证明发生了铁电相变。     

溶胶凝胶法制备钛酸锶钡(Ba1-xSrx)TiO3陶瓷及其介电性能的研究

采用硝酸钡、硝酸锶、钛酸丁酯和柠檬酸为原料的配合物溶胶凝胶方法制备了(Ba1-xSrx)TiO3(BST)陶瓷.实验结果表明,BST粉体合成温度及烧结温度分别为700及1250℃,均低于传统工艺的相应温度. Sr含量x≥0.40,(Ba1-xSrx)TiO3陶瓷的相结构为立方钙钛矿相;Sr含量x＜0.40,(Ba1-xSrx)TiO3陶瓷的相结构为四方钙钛矿型. (Ba1-xSrx)TiO3(0.5≤x≤0.70)陶瓷的电容率随温度变化曲线,说明存在由铁电四方相到顺电立方相的相变.且随锶(Sr)的摩尔量x的增加,(Ba1-xSrx)TiO3陶瓷样品的相变温度向低温方向移动,相变温度Tc的移动关系为Tc=394.1-272.6x(K).     

氧化锆增韧陶瓷（ZTC）的晶界结构

本文用 JEM200CX 超高分辨型透射电子显微镜对 ZTC 陶瓷的晶界结构进行了研宄。发现 Al_2O_3与ZrO_2之间的晶界存在共格点、共渗和无序结构形式,并发现晶界处常为 ZrO_2相变的成核区。ZrO_2(m)和ZrO_2(t)之间的晶界,既能成为 ZrO_2相变的成核区,也能阻止 ZrO_2相变的延续发展。只有当两个 ZrO_2晶粒的同类型晶面取向相近时,ZrO_2的相变才容易通过晶界而发展。ZrO_2(t)和 ZrO_2(t)之间的晶界具有较好的共格点结构,形成交错的锯齿状,这是 TZP 陶瓷具有高强和高韧的原因之一。     

Mn掺杂BaTiO3基PTCR陶瓷相变的EPR研究

为了探索利用EPR谱线对PTCR陶瓷相变及PTC效应的机制研究的可能性,本文对掺Mn的BaTiO3基正温度系数热敏电阻（简称PTCR）陶瓷在120-450K温度范围内的电子顺磁共振谱进行了研究。得于了Mn^2 离子EPR信号强度、g因子值和超精细耦合常数|A|值的温度分布,发现EPR参数与PTCR陶瓷相变有明显的对应关系,并给出微观结构上的初步解释。研究表明EPR谱线以及精细结构的分析可以为PTCR陶瓷的相变机制以及上的初步解释。研究表明EPR谱线以及精细结构的分析可以为PTCR陶瓷的相变机制以及PTC效应的机制研究提供新的途径。     

SrCO3掺杂对PMN-PMnN-PZT-Ce压电陶瓷储能及介电弛豫性能的影响

通过铌铁矿先驱法制备了Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)+xSrCO_3(PMN-PMnN-PZT-Ce-xSr,x=0.00,0.03,0.05,0.07)四元系压电陶瓷,研究了SrCO_3含量的变化对Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)-Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)(PMN-PMnN-PZT-Ce)压电陶瓷相结构、储能密度以及弛豫行为的影响。通过XRD表明,样品为单一稳定的钙钛矿结构,并且存在准同晶界(MPB);当x=0.07时,在外加电场60kV/cm下取得较好的储能性能:储能密度W1=0.31J/cm~3,储能效率η=0.47;通过修正Curie-Weise定律,较好地描述了陶瓷弥散相变的特征,弥散相变系数γ随着Sr~(2+)掺杂量的增加而增加。当x=0.07时,γ取得最大值1.972 8,此时弛豫现象最明显。     

铌酸钾钠基无铅压电陶瓷的相变特性和掺杂改性研究进展

人类社会可持续发展的要求以及一些发达国家有关电子产品无铅化法规的全面实施,近年来无铅压电陶瓷的研究与开发受到极大关注.碱金属铌酸盐系压电陶瓷以其优越的压电性能和较高居里温度受到人们高度重视.结合近年有关KNbO3-NaNbO3(KNN)基无铅压电陶瓷的报道,着重从KNN基压电陶瓷的相变特性、掺杂改性和引入第三组元等几个方面,介绍了相关研究的现状,并对KNN基压电陶瓷的发展趋势进行了展望.     

Temperature dependence of the elastic and inelastic moduli of YBa2Cu3O7−δ ceramics

Elastic and inelastic moduli of the superconducting yttrium-barium oxide ceramics YBa₂Cu₃O_7−δ (YBCO) were studied using the ultrasonic resonance technique. In the range from room temperature up to the temperature of the ortho-tetra phase transition, the elastic and inelastic moduli of YBCO samples exhibit a number of anomalies. It is shown that these features are related to the behavior of active oxygen in the ceramics, the phase inhomogeneity of the material, and the phase transitions.     

Construction of new morphotropic phase boundary in 0.94(K0.4?xNa0.6BaxNb1?xZrx)O3–0.06LiSbO3 lead-free piezoelectric ceramics

0.94(K_0.4−x Na_0.6Ba _x Nb_1−x Zr _x )O₃–0.06LiSbO₃ ceramics were prepared by conventional technique, and the effect of BaZrO₃ on the phase transitions, dielectric, ferroelectric, and piezoelectric properties of the ceramics were investigated. The phase transitions for the ceramics were determined by the temperature dependence of dielectric properties and X-ray diffraction patterns. BaZrO₃ changes the symmetry of the ceramics from tetragonal dominant phase with x = 0–0.06 to rhombohedral phase with x = 0.07–0.09. The phase transition near room temperature for the composition with x ~ 0.06 is different from previously reported phase transition between orthorhombic and tetragonal phases. It is suggested that a new morphotropic phase boundary (MPB) is constructed with both rhombohedral–orthorhombic and orthorhombic–tetragonal phase transitions near room temperature, and the enhanced piezoelectric properties (d ₃₃ = 344 pC/N and k _P = 32.4% with x = 0.06) are obtained. The results indicate that the construction of new MPB is of significance for further development of KNN-based ceramics.     

Ba1-xSrxTi0.88Sn0.12O3陶瓷结构与介电性能的研究

采用高温固相烧结法制备了Ba1-xSrxTi0.88Sn0.12O3(x=0.10,0.20,0.30,0.40,0.50)陶瓷,研究了Sr含量及烧结温度对Ba1-xSrxTi0.88Sn0.12O3陶瓷结构与介电性能的影响.XRD初步分析表明Ba1-xSrxTi0.88Sn0.12O3陶瓷在室温为立方钙钛矿结构.进一步的研究表明Ba1-xSrxTi0.88Sn0.12O3陶瓷的介电性能与对A位、B位进行的离子取代密切相关.随着Sr含量的增加,不同烧结温度下Ba1-xSrxTi0.88Sn0.12O3陶瓷的介电性能下降,相变温度Tc移向低温.尽管在所研究的组分范围内Ba1-xSrxTi0.88Sn0.12O3表现出扩散相变铁电体的特征,但是典型的介电弛豫行为并没有被观察到.     

The effect of annealing on the photoacoustic and photothermal response of Al2O3-SiC-TiC ceramics with internal stresses

The Vickers indentation zones in Al₂O₃-SiC-TiC ceramics were studied by scanning laser photo-deflection and photoacoustic microscopy. The method of photoacoustic microscopy with piezoelectric detector (PAMPD) is sensitive to the internal stress distribution in the material. The effect of annealing on the PAMPD signal of the Al₂O₃-SiC-TiC ceramics was studied. An increase in the annealing time is accompanied by decrease in the PAMPD response from the vertices of radial cracks.     

Investigating phase transitions and strength in single-crystal sapphire using shock–reshock loading techniques

This paper focuses on developing a technique that can probe phase transitions in ceramics and evaluating strength properties of single-crystal sapphire. High strength ceramics that undergo solid-to-solid polymorphic phase transitions can display a wide range of volume changes. Materials with large volumetric changes can be easily detected; however, materials demonstrating small volume changes, pose a different experimental problem. Because of the variety of diagnostics tools (for acquiring data), and differing interpretation of the data, materials that undergo small volume changes, make detection of transformation quite challenging. Different experimental test methods are needed to potentially allow detection and characterization of materials undergoing phase transitions with small volume changes. In addition, these results show that single-crystal sapphire has considerable strength loss at approximately 56 GPa on the Hugoniot. In this study, we report loading profile measurements in the form of particle velocity histories for single-crystal sapphire that is shocked to a given stress level directly or through multiple steps from a shocked state of 56 GPa. We probe the region of suggested phase transformations utilizing the simplest type of off-Hugoniot reshock loading. This also allows an assessment of shear strength in the shocked state of single-crystal c-axis sapphire. The present measurements show no evidence of a phase transition, but do suggest considerable strength loss in sapphire.     

非化学计量比对(K0.465Na0.465Li0.07)(Nb0.95Sb0.05)O3无铅压电陶瓷结构及性能的影响

通过传统固相合成工艺制备了(K0.465+xNa0.465+yLi0.07)(Nb0.95-zSb0.05)O3(x,y,z=-0.01～0.02)无铅压电陶瓷,研究了非化学计量比对陶瓷结构及压电性能的影响。结果表明符合化学计量比的陶瓷具有四方钙钛矿结构;在实验范围内,K和Nb的过量或少量均不会改变体系的相结构,而Na过量将会导致体系正交-四方相变温度升高到室温以上,并且正交-四方相变温度随y的增加而升高;过量添加约0.5%(摩尔分数)的K或Na便能补偿在高温烧结时的碱金属元素的挥发损失,进而提高陶瓷的压电性能;该体系陶瓷的组分在较大范围内变化时(如当y=z=0时,x=0～0.02;当x=z=0时,y=0～0.01;以及当x=y=0时,z=-0.01～0.005),仍然能保持d33>200pC/N和kP>40%这样较好的性能。上述结果不仅有利于在研究中材料制备工艺的重复,而且有利于当材料在器件应用时所面临的规模化生产。     

Raman scattering study of Ca-modified lead titanate

The paraelectric to ferroelectric phase transitions were studied by Raman scattering in Ca-doped lead titanate ceramics. The soft optic modes responsible for the ferroelectric phase transitions were clearly observed. The A(1)(1TO) mode, which softens toward T(c), contains four subpeaks. The frequencies of these subpeaks depend to a great extent on the Ca content and the temperature. These behaviors are discussed on the basis of the anharmonicity of lattice vibrations.     

Raman scattering study on ferroelectric (Ba0.32Sr0.68)2Nb2O7 ceramics

Raman scattering technique was applied to examine the Ba-doping effect to the two low temperature phase transitions of Sr₂Nb₂O₇ (SN) in the temperature range from −190 to 600 °C. The line shape of Raman spectra can be well fitted by multidamped harmonic oscillator model. We did not observe any soft mode related to the two low temperature phase transitions corresponding to those of the pure SN. It is correlated to the disappearance of the incommensurate phase in (Ba_0.32Sr_0.68)₂Nb₂O₇ ceramics. However, the temperature dependence behavior of the three low frequency modes indicates another new structural phase transition around 270 °C. It is considered that the reduction of the interlayer interaction caused by partial replacement of Sr-site by Ba-site, whose ionic radius is larger than that of Sr, may be the reason for the disappearance of the incommensurate phase transition in (Ba_0.32Sr_0.68)₂Nb₂O₇ ceramics.     

Phase transitions in zirconium dioxide and related materials for high performance engineering ceramics

Because of its outstanding mechanical properties, zirconia-based ceramics are considered as some of the best potential materials within the engineering ceramics field that might be widely used to substitute various metallic parts and specific alloys. Taking into account the transformation toughening mechanisms that operates in their microstructure, important properties can be obtained. Phase transitions as well as transformation toughening in ZrO₂ are reviewed briefly with the purpose to understand its effects in some composites and glass systems. Zirconia ceramics as high toughness materials for cutting tool, metal forming applications, mechanically superior ceramics called partially stabilised zirconia (PSZ), solid electrolytes, have been fabricated using the martensitic nature of the tetragonal to monoclinic phase transition.     

Fabrication of Lead Zirconate Titanate Powder Using Ultrasonic Ball Milling Technique

In this research, the ultrasonic ball milling technique has been used to fabricate lead zirconate titanate （PZT） ceramics. PZT with the composition nearly the morphotropic phase boundary （MPB） ： Pb（Zr0.52 Ti0.48 ）03 was studied. The effect of milling time on phase formation of sample powder was examined by X-ray diffraction technique （XRD）. Moreover, the physical, dielectric, piezoelectric properties and microstructure of PZT ceramics were investigated. The present results reveal that the ultrasonic ball milling technique results the homogeneous and small size of PZT powder. Furthermore, there is a significantly change occurs in the size of the particles with the short time of milling process.