K改性的BNT-BZT压电陶瓷制备与性能研究

无铅压电陶瓷是压电材料中一个重要的研究方向，为了能够取代目前广泛应用的含铅材料，需要进一步提高无铅陶瓷材料的各项性能，尤其是压电性能。BNT-BZT系陶瓷是钛酸铋钠（BNT）和锆钛酸钡（BZT）两相形成的固溶体，在BNT-BZT陶瓷体系中，富BNT和低Zr含量的区域存在准同型相界，在相界附近可以得到性能优良的无铅压电陶瓷，其性能以3大约150pC/N，居里温度在240℃左右，介电常数大约900。在BNT-BZT相界点处掺杂K离子，研究了K改性的BNT-BZT体系陶瓷的微观结构与性能。实验结果表明，以3达到165pC／N；居里温度达到270℃；烧结中出现了玻璃相，预烧温度和烧结温度相对于原体系都有适当降低。     

(Bi0.5Na0.5)TiO3-Ba(Ti,Zr)O3固溶体无铅压电陶瓷

改善烧结制度制备(Bi0.5Na0.5)TiO3-Ba(Ti,Zr)O3(简称BNT-BZT)系无铅压电陶瓷,能得到较高的致密度.该压电陶瓷具有良好的电学性能.电学性能的最佳成分点位于准同型相界附近四方相的区域,组成为(Bi0.5Na0.5)TiO3-xBa(TiyZr)O3x=0.09～0.12的范围内,此时具有最大的压电常数(d33=147pC/N)和室温介电常数(ε33T/ε0=881.4).BNT-BZT陶瓷体系的机电耦合系数Kp受BZT含量的影响较小,而BZT含量对机械品质因数Qm的影响较大.     

（Bi0．5Na0．5）TiO3-（Bi0．5K0．5）TiO3陶瓷在准同型相界附近的铁电和压电性能

通过传统的固相烧结法合成（1-x）（Bi0.5Na0.5）TiO3-x（Bi0.5K0.5）TiO3陶瓷（x选取范围0．135-0．24）。先在850℃合成原料粉体，然后在1100～1200℃下烧结得到陶瓷样品。分析检测该体系陶瓷的结构以及铁电、压电性能。x射线衍射分析结果表明，该二元系准同型相界（MPB）区域位于x=0．165～0．225附近。对这一体系铁电和压电性能进行测试，并对其在准同型相界附近的电学性能发生变化的机理作了讨论。（Bi0．5Na0．5）TiO3-（Bi0.5K0.5）TiO3是一种很有应用前景的无铅压电陶瓷材料，值得进一步的研究和探索。同时，本实验还对密封烧结工艺对无铅压电陶瓷性能的影响作了初步的研究。     

传统工艺制备铌酸钾钠基无铅压电陶瓷的性能控制

介绍了采用传统陶瓷制备工艺,为获得晶粒细小、组织致密、性能良好的铌酸钾钠基无铅压电陶瓷,目前所采取的性能控制措施,即添加助烧剂、掺杂改性、添加第二组元、准同型相界的研究及调整n(Na)/n(K),来调整NKN陶瓷的性能。展望了NKN基无铅压电陶瓷的发展趋势。     

高居里点BiScO3-PbTiO3压电陶瓷介电压电性能研究

用通常的固相反应法制备了(1–X)BiScO3-XPbTiO3(X=0.60,0.62,0.64,0.66,0.68)系压电陶瓷,并对其进行了微结构和介电、压电性能研究。XRD分析表明,该系统在PbTiO3摩尔分数X=0.64时,存在准同相界,当X小于0.64或大于0.64时,陶瓷分别为菱方相和四方相结构。相结构在准同相界的试样具有最大的压电常数,其d33高达430pC/N。介温谱测试表明,该陶瓷体系居里温度为450℃左右,具有弛豫铁电体特征。     

PNS-PZ-PT压电陶瓷烧结和性能的研究

对Pb(Ni1/3Sb2/3)-PbZrO3-PbTiO3陶瓷烧结和压电性能的研究表明:当含有48mol%PbTiO3和少于10mol%Pb(Ni1/3Sb2/3)的粉体在850℃下煅烧2 h,得到单一钙钛矿结构,但是如果Pb(Ni1/3Sb2/3)组成在12mol%～14mol%之间时,则三方相和四方相共存.所以材料的准同相界在Pb(Ni1/3Sb2/3)=12mol%,PbZrO3=40mol%,PbTiO3=48mol%.当该组分在1260℃至1280℃烧结时得到的烧结物密度最大为7.8g/cm3.扫描电镜结果表明在1280℃时材料烧结气孔率最小.当处于准同相界的组分在1280℃烧结时,材料的机电耦合系数Kp和机械品质因数Qm分别达到最大值0.488和最小值292.5.     

PNS-PZ-PT压电陶瓷烧结和性能的研究

对Pb(Ni1/3Sb2/3)-PbZrO3-PbTiO3陶瓷烧结和压电性能的研究表明当含有48mol%PbTiO3和少于10mol%Pb(Ni1/3Sb2/3)的粉体在850℃下煅烧2 h,得到单一钙钛矿结构,但是如果Pb(Ni1/3Sb2/3)组成在12mol%～14mol%之间时,则三方相和四方相共存.所以材料的准同相界在Pb(Ni1/3Sb2/3)=12mol%,PbZrO3=40mol%,PbTiO3=48mol%.当该组分在1260℃至1280℃烧结时得到的烧结物密度最大为7.8g/cm3.扫描电镜结果表明在1280℃时材料烧结气孔率最小.当处于准同相界的组分在1280℃烧结时,材料的机电耦合系数Kp和机械品质因数Qm分别达到最大值0.488和最小值292.5.     

(1-4x)NBT-3xKBT-xBT系无铅压电陶瓷性能研究

采用传统固相法制备了(1-4x)NBT-3xKBT-xBT(x=0.020～0.035)体系压电陶瓷.通过XRD分析,发现该体系陶瓷都能形成单一的钙钛矿型固溶体,并在0.025≤x≤0.032范围内具有三方和四方共存结构,为该体系的准同型相界.当x=0.028时,d_(33)=162 pC/N,Q_m=203.29,k_p=0.234.同时分析了该体系陶瓷材料在1, 10, 100 kHz下介电常数-温度曲线和介电损耗-温度曲线,发现该体系陶瓷样品的介电温谱都存在两个介电反常峰,且介电常数和介电损耗与频率存在很强的依赖性,表明该体系材料具有弛豫型铁电体性质.     

AgNbO3-BaTiO3陶瓷在准同型相界附近的电学性能研究

最近的理论工作预期，可能存在一种新的无铅压电陶瓷xAgNbO3-（1-x）BaTiO3，认为在含12％AgNbO3的组分处存在准同型相界（MPB），具有良好的性能，并有较高的居里点。但是尚未见到有关这方面的实验报道。通过传统的固相反应法合成xAgNbO3-（1-x）BaTiO3陶瓷，其中取x等于0．08到0．16。首先在950℃下预烧3h合成AgNbO3-BaTiO3，然后将粉末球磨、压片后，在1150℃下进一步烧结得到样品。通过X射线衍射技术（XRD），研究了xAgNbO3-（1-x）BaTiO3的相结构，并对这一体系的电学性质进行了测试。发现x=0．12附近存在着MPB，且介电常数达到1000左右，剩余极化强度达到3．5μC／cm^2，矫顽场反为800V／mm。xAgNbO3-（1-x）BaTiO3作为一种可供选择的无铅压电陶瓷值得进一步的研究和开发。     

无铅压电陶瓷及其应用研究

随着社会可持续发展战略的实施和人们环境意识的加强，无铅压电陶瓷及其应用已成为了当前铁电压电材料及其应用研究的热点。本文根据近期国内外有关无铅压电陶瓷的发展，结合本课题组肖定全教授等近年在无铅压电陶瓷的研究，对无铅压电陶瓷的研究进展及应用现状进行了综述，重点介绍了BaTiO3基、Bi1／2Na1／2TiO3基、碱金属铌酸盐基、钨青铜结构和铋层状结构五大体系无铅压电陶瓷的性能、本课题组主要发明的无铅压电陶瓷体系以及BNT基无铅压电陶瓷在滤波器上的应用和发展前景。     

M3Gd(PO4)3:Tm3+(M=Mg,Ca,Sr,Ba)真空紫外发光特性

研究了M3Gd(PO4)3Tm3+(M=Sr,Ba,Ca,Mg)样品的结构特性、发光特性.M3Gd(PO4)3Tm3+属于立方晶系.基质掺入铥离子后其结构没有明显变化.M3Gd(PO4)3Tm3+在166 nm和210 nm附近有强烈的吸收峰.位于166 nm附近的强烈吸收峰归因于基质的强烈吸收,210 nm附近的吸收峰则归因于Gd3+的8S7/2-6GJ的能级跃迁.在166 nm真空紫外光激发下,样品在453 nm及363 nm处有较强的发射峰,发射主峰位于453 nm.随着样品中阳离子的变化,M3Gd(PO4)3Tm3+的激发峰发生强烈变化,从而导致其发射光谱有了较大变化.     

Enthalpies of Formation of (Cu,Ni)3Sn, (Cu,Ni)6Sn5-HT and (Ni,Cu)3Sn2-HT

Standard enthalpies of formation of ternary phases in the Cu-Ni-Sn system were determined along sections at 25, 41 and 45.5 at.% Sn applying tin solution drop calorimetry. Generally, the interaction of Ni with Sn is much stronger than that of Cu with Sn. Along all sections the enthalpy of formation changes almost linearly with the mutual substitution of Cu and Ni within the respective homogeneity ranges. Thus no additional ternary interaction promoting the formation of further Cu-Ni-Sn phases can be assumed. The results are discussed and compared with literature values relevant to this system.     

Double-walled carbon nanotube (DWCNT)–poly(3-octylthiophene) (P3OT) composites: Electrical,optical and structural investigations

In the present study, we report experiments based on in situ polymerization of 3-octylthiophene with DWCNT and many hitherto unstudied properties for the first time. The specialty of DWCNT being the inner tube retaining its intrinsic electronic and optical properties, while the outer tube could be involved in the composite formation. From the IR aromatic and out-of-plane C–H stretching frequencies, the interaction between the polymer and the nanotubes is probed. Further to this absorption spectroscopy, photoluminescence and Raman measurements were carried out to characterize the composites. The conductivity contributions of the nanotubes and Hall voltage measurements are used to understand the utility of the composites for solar cell applications.     

Synthesis,characterization,and thermostability of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(Ⅱ)

Owing to the adaptability to large scale processing,excellent composition control and film uniformity,the metal-organic chemical vapor deposition(MOCVD)technique is a promising process for high-temperature superconductor YBa2Cu3O7-δ(YBCO)preparation.In this technique,the evaporation characteristics and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO film.In the present report,bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(Ⅱ)(Cu(TMHD)2)was synthesized by the interaction of copper acetate hydrate with TMHD in methanol solution,and its structure was identified by FTIR,1H NMR,and EI-MS spectroscopy.Subsequently,thermal property and the kinetics of decomposition were systematically investigated by nonisothermal thermogravimetric analysis methods(TGA)at different heating rates in streams of N2,and the average apparent activation energy of evaporation process was evaluated by the Ozawa,Kissinger,and Friedman methods.The possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 85.1 kJ·mol-1.     

Dislocation density in Ni3(Al,Hf)

The temperature dependence of dislocation density and its relationship with the anomalous growth of the flow stress are presented. A pronounced density increase of about one order of magnitude in a temperature range below the peak of anomalous flow stress growth has been clearly established experimentally. The correlation with different components of the applied stress is examined and it is shown that the dislocation density is related to the stress required for dislocation multiplication.     

Conductive poly(α,ω-bis(3-pyrrolyl)alkanes)-coated wool fabrics

Cross-linked poly(α,ω-bis(3-pyrrolyl)alkanes) were directly applied to woven wool substrates by either chemical, vapour or mist polymerization methods. Choice of dopant could greatly improve the surface resistance. The optimum coating on textiles with the lowest surface resistance, highest colour-fastness and stability was achieved using a mist polymerization method with 1,8-bis(pyrrolyl)octane, iron(III) chloride (FeCl₃) as the oxidant and p-toluene sulfonic acid sodium salt (pTSA) as the dopant.     

Synthesis and photoluminescence properties of Eu(pzc)3(phen) and Eu(mpzc)3(phen)

Novel europium(III) complexes, (2-pyrazinecarboxylato)(phenanthroline) europium(III) [Eu(pzc)₃(phen)] and (5-methyl-2-pyrazinecarboxylato) (phenanthroline)europium(III) [Eu(mpzc)₃(phen)] have been designed and synthesized. These complexes were characterized by FT-IR, UV-Vis, and X-ray photoelectron spectroscopy. Photoluminescence (PL) studies showed that the two complexes emitted remarkably red luminescence. When powder samples of Eu(pzc)₃(phen) and Eu(mpzc)₃(phen) were examined using time-resolved spectroscopic analysis, the luminescence lifetimes were found to be 1.05 and 2.36 ms, respectively. Thermogravimetric analysis showed that the europium complexes possessed good thermal stability up to 345–350 °C.     

Effect of a nanosized state on the magnetic properties of Ni3(Al,Fe) and Ni3(Al,Co)

An analysis of the magnetic properties of the binary Ni₃Al intermetallic compound (unalloyed and alloyed with iron and cobalt) after high-pressure torsion has been carried out. For all of the alloys studied, the deformation using ten revolutions of the anvils at 10 GPa results in the formation of a nanocrystalline condition. After the deformation, a significant decrease takes place in both the magnetic susceptibility of the Ni₃Al alloy and magnetization of the Ni₃Al-Co intermetallic compound. The initially ferromagnetic Ni₃Al-Fe alloy becomes paramagnetic at room temperature.