溶胶-凝胶法制备(Na0.5Bi0.5)TiO3-BaTiO3基无铅压电陶瓷的研究

采用溶胶-凝胶法制备（Na0.5 Bi 0.5）TiO3-BaTiO3超细粉体。研究结果表明，当热处理温度为800℃时能合成出纯的钙钛矿结构的BNBT超细粉体。另外研究发现，与固相法合成的陶瓷样品相比，sol-gel法制备的陶瓷样品的压电常数和机械品质因子有所提高，但其它的电学性能与固相法合成的陶瓷相近，如介电常数、介电损耗等。     

Na_(0.5)Bi_(0.5)TiO_3陶瓷介电性能的实验研究

采用柠檬酸盐-自燃烧法制备Na0.5Bi0.5TiO3无铅压电陶瓷,系统地研究了制备工艺条件对陶瓷性能和结构的影响。柠檬酸浓度、溶液pH值、烧结温度制度对陶瓷的压电性能有很大的影响。当柠檬酸浓度C=9%,pH=8.5,烧结温度为1130℃时,陶瓷具备最大的压电常数,d33可达71.2pc/n。1130℃烧结陶瓷的XRD表明,陶瓷已形成单一钙钛矿结构的钛酸铋钠主晶相。     

溶胶-凝胶法合成(Na0.5Bi0.5)TiO3微粉

以钛酸四丁酯、硝酸铋、醋酸钠和冰醋酸为原料,利用溶胶-凝胶工艺得到透明凝胶,经干燥后煅烧成(Na0.5Bi0.5)TiO3微粉。通过对溶胶体系水/醇盐的摩尔比、初始pH值及胶凝温度对(Na0.5Bi0.5)TiO3凝胶体系溶胶-凝胶形成过程影响的研究,发现水/醇盐比R在35≤R≤60,pH在2.2~3.5,反应温度在40~60℃时,能够得到透明的溶胶;通过TG-DTA、SEM、X-ray等分析手段对(Na0.5Bi0.5)TiO3粉体进行测试,表明在650℃合成1h可以得到单一钙钛矿(Na0.5Bi0.5)TiO3晶体;采用TEM对(Na0.5Bi0.5)TiO3干凝胶粉体分析其粒径大小约为10nm。     

Bi0.5Na0.5TiO3基无铅压电陶瓷设计与制备研究的新进展

综述了Bi0.5Na0.5TiO3(BNW)基无铅压电陶瓷体系研究的最新进展,介绍了BNT基无铅压电陶瓷的设计方法及其制备技术.用自洽场离散变分法(self-consult charge-discrete variation-Xa,SCC-DV-Xa)等计算方法可为设计新型BNT基陶瓷提供重要的理论指导.用湿化学法,包括:溶胶-凝胶法、柠檬酸盐法、水热法等,可以合成BNT基纳米粉体,该类方法制备的BNT基粉体具有良好烧结活性,利于致密化烧结,使材料电性能得到改善.用模板晶粒生长技术可获得晶粒生长定向程度很高的BNT基压电陶瓷材料,进而提高材料在特定方向的压电性能.     

二步法合成低温烧结（MQ，Zn）TiO3介电陶瓷

首先采用固相法合成了（Mg，Zn）2TiO4粉体，然后将钛酸丁酯水解制备出TiO2溶胶，再利用TiO2溶胶对已合成的（Mg，Zn）2TiO4粉体进行包覆。包覆后的粉体经500℃预烧后在1150℃烧结成瓷，采用XRD、SEM分别做了样品的物相和显微结构分析，测试结果表明：当TiO2，（Mg，Zn）2TiO4为1．1时，合成产物为纯的（Mg，Zn）TiO3相。在1MHz下测试了样品的介电性能，结果表明：当TiO2／（Mg，Zn）2TiO4为1．1，烧结温度为1150℃时，陶瓷介电性能最好。     

（1–x）（K_（0.48）Na_（0.48）Li_（0.04））NbO_3–x（Na_（0.8）K_（0.2））_（0.5）Bi_（0.5）TiO_3无铅压电陶瓷的相变行为及其压电性能

采用固相法应法制备了（1–x）（K0.48Na0.48Li0.04）NbO3–x（Na0.8K0.2）0.5Bi0.5TiO3无铅压电陶瓷,研究了不同x（0,0.5%,1.0%,1.5%,2.0%,3.0%）对材料的相结构、介电性能以及压电性能的影响。结果表明：随着x增加,样品的Curie温度TC与正交到四方相变温度TO–T均逐渐降低,而压电常数d33与机电耦合系数kp均先升高后降低;该体系在0.5%     

新品研发辑要

水热法合成Na0.5Bi0.5TiO3纳米陶瓷粉体简介:无铅压电陶瓷的研究开发是功能陶瓷研究的重要内容之一。其中,钛酸铋钾(缩写为KBT)是无铅压电体系的重要候选材料之一,为钙钛矿结构铁电体,室温时为四方晶系,居里点380℃。目前,该体系的合成多采用传统固相法,得到的KBT粉体较粗(微米     

湿化学法制备高性能PTC粉体的研究

采用草酸盐共沉淀法和柠檬酸盐溶胶-凝胶二步合成法两种湿化学法合成了高性能的PTC粉体。草酸盐共沉淀法制备的PTC粉体平均粒径为200nm，粉体部分团聚；柠檬酸盐溶胶-凝胶二步合成法得到了纳米级的PTC粉体，平均粒径为70nm，粒度分布均匀，分散性较好。讨论并分析比较了两种合成方法的粉体形成历程、机理和微观形貌，两种方法比较，后者所得粉体化学组成更为均匀、晶型发育更为完全。     

国内工业陶瓷文献题录及文摘（四十一）

流延法制备铌酸钾钠无铅压电陶瓷的工艺研究·陶瓷学报,2011,01以Na2CO3,K2CO3,Nb2O5等为原料,采用固相法合成了K0.5Na0.5NbO3的粉体,并以此粉体为主要原料,添加适量的分散剂、粘结剂及除泡剂制备浆料,采用流延法制备K0.5Na0.5NbO3膜片,研究了K0.5Na0.5NbO3固相含量、分散剂、粘结剂及除泡剂的种类及含量对流延浆料流延性能和对K0.5Na0.5NbO3陶瓷的影响。     

Bi_(1/2)Na_(1/2)TiO_3-BaTiO_3系无铅压电陶瓷制备工艺的优化及其结构分析

借助正交试验设计,通过对无铅压电陶瓷压电、介电性能的测试,研究了BaTiO3含量、预烧温度、烧结温度及保温时间对(1-x)(B i1/2Na1/2)TiO3xBaTiO3(简写为BNBT 100x)陶瓷性能的影响。研究结果表明制备BNBT系陶瓷的最优化工艺条件为:BaTiO3摩尔分数x=0.06、预烧温度850℃、烧结温度1 130℃、保温时间2 h。通过XRD分析了BNBT系压电陶瓷的晶体结构类型、晶胞参数及晶格畸变随着BaTiO3摩尔分数的变化,确定了该体系的三方四方的准同型相界在x=0.06~0.08之间。     

Piezoelectric K0.5Na0.5NbO3 Ceramics Textured Using Needlelike K0.5Na0.5NbO3 Templates

Improved performance by texturing has become attractive in the field of lead‐free ferroelectrics, but the effect depends heavily on the degree of texture, type of preferred orientation, and whether the material is a rotator or extender ferroelectric. Here, we report on successful texturing of K_0.5Na_0.5NbO₃ (KNN) ceramics by alignment of needlelike KNN templates in a matrix of KNN powder using tape casting. Homotemplated grain growth of the needles was confirmed during sintering, resulting in a high degree of texture parallel to the tape casting direction (TCD) and the aligned needles. The texture significantly improved the piezoelectric response parallel to the tape cast direction, corresponding to the direction of the strongest <001>_pc orientation, while the response normal to the tape cast plane was lower than for a nontextured KNN. In situ X‐ray diffraction during electric field application revealed that non‐180° domain reorientation was enhanced by an order of magnitude in the TCD, compared to the direction normal to the tape cast plane and in the nontextured ceramic. The effect of texture in KNN is discussed with respect to possible rotator ferroelectric properties of KNN.     

四元复合氧化物La_(0.5)Sr_(0.5)Ni_(0.5)Cu_(0.5)O_3的抗硫性能

以SO2 为毒物 ,采用脉冲中毒方法 ,再以CO氧化反应为探针 ,对三元复合氧化物催化剂La0 .5Sr0 .5NiO3 与La0 .5Sr0 .5CuO3 以及四元复合氧化物催化剂La0 .5Sr0 .5Ni0 .5Cu0 .5O3 等三种催化剂样品的抗硫毒能力、失活曲线、中毒催化剂的再生性能以及毒物残留形态等进行了全面考察和对比分析。实验结果表明四元复合氧化物催化剂La0 .5Sr0 .5Ni0 .5Cu0 .5O3 在SO2 毒物含量是 1 2 2×10 -2 mmol时 ,特别是在高温 (≥ 30 0℃ )条件下 ,具有优异的抗硫性能     

Thermally-stable large strain in Bi(Mn0.5Ti0.5)O3 modified 0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3 ceramics

(1-x)[0.8Bi_0.5Na_0.5TiO₃-0.2Bi_0.5K_0.5TiO₃]-xBi(Mn_0.5Ti_0.5)O₃ (x = 0–0.06, BNKMT100x) lead-free ferroelectric ceramics were prepared via solid state reaction method. Bi(Mn_0.5Ti_0.5)O₃ induces a structure transition from rhombohedral-tetragonal morphotropic phases to pseudo-cubic phase. Moreover, the wide range of compositions within x = 0.03–0.055 exhibit large strain of 0.31%–0.41% and electrostrictive coefficient of 0.027–0.041 m⁴/C². Especially, at x = 0.04, the large strain and electrostrictive coefficient are nearly temperature-independent in the range of 25–100 °C. The impedance analysis shows the large strain and electrostrictive coefficient originate from polar nanoregions response due to the addition of Bi(Mn_0.5Ti_0.5)O₃.     

Na0.5Bi0.5TiO3-Ba0.5Sr0.5Nb2O6无铅压电陶瓷的研究

采用固相法制备了(1-x)(Na0.5Bi0.5)TiO3-xBa0.5Sr0.5Nb2O6(0≤x≤1.0％)(简称(1-x)NBT-xBSN)无铅压电陶瓷,研究了不同BSN含量(x=0,0.1％,0.3％,0.5％,0.7％,1.0％,摩尔分数)样品的物相组成、显微结构及电性能.结果表明:所有样品均为纯钙钛矿结构,随掺杂量x的增加,陶瓷的相对密度pr、压电常数d33和机电耦合系数kp均先增大后降低,机械品质因子Qm和退极化温度Td则逐渐下降.该体系陶瓷具有弥散相变特征,弥散指数介于1.6～1.7.当x=0.5％时,陶瓷获得最佳性能:d33=92pC/N,kp=0.164,Qm=89,εr=650,tanδ=5.47％,pr=96.5％.     

Near-infrared emitting CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots: synthesis and bright luminescence

We present how CdTe_0.5Se_0.5 cores can be coated with Cd_0.5Zn_0.5S shells at relatively low temperature (around 200°C) via facile synthesis using organic ammine ligands. The cores were firstly fabricated via a less toxic procedure using CdO, trioctylphosphine (TOP), Se, Te, and trioctylamine. The cores with small sizes (3.2-3.5 nm) revealed green and yellow photoluminescence (PL) and spherical morphologies. Hydrophobic core/shell CdTe_0.5Se_0.5/Cd_0.5Zn_0.5S quantum dots (QDs) with tunable PL between green and near-infrared (a maximum PL peak wavelength of 735 nm) were then created through a facile shell coating procedure using trioctylphosphine selenium with cadmium and zinc acetate. The QDs exhibited high PL efficiencies up to 50% because of the formation of a protective Cd_0.5Zn_0.5S shell on the CdTe_0.5Se_0.5 core, even though the PL efficiency of the cores is low (≤1%). Namely, the slow growth process of the shell plays an important role for getting high PL efficiencies. The properties of the QDs are largely determined by the properties of CdTe_0.5Se_0.5 cores and shells preparation conditions such as reaction temperature and time. The core/shell QDs exhibited a small size diameter. For example, the average diameter of the QDs with a PL peak wavelength of 735 nm is 6.1 nm. Small size and tunable bright PL makes the QDs utilizable as bioprobes because the size of QD-based bioprobes is considered as the major limitation for their broad applications in biological imaging.     

K0.5Na0.5NbO3-BaCu0.5W0.5O3无铅压电陶瓷的结构与性能

以传统固相法工艺制备(1-x)K0.5Na0.5NbO3-xBaCu0.5W0.5O3[(1-x)KNN-xBCW]无铅压电陶瓷,研究不同BCW掺量(x=0％,0.1％,0.25％,0.5％,1.0％,摩尔分数,下同)对KNN陶瓷的晶体结构和电性能的影响,结果表明:x＜0.5％时,KNN陶瓷的相结构没有改变,仍为正交相...     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的极化工艺研究

主要研究了极化电场,极化时间和极化温度等工艺参数对Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷介电和压电性能的影响。结果表明:极化电场和极化温度对压电陶瓷的介电、压电性能影响较大,而极化时间则影响较小。适宜的极化电场是3～3.5kV/mm,极化温度70～80℃,极化时间为10～15min。     

CeO2掺杂钛酸铋钠钾陶瓷的制备工艺与介电性能

为了进一步探索合成工艺对钛酸铋钠系无铅材料的结构及介电特性的影响,本文以甘氨酸为燃料,利用固相-燃烧法制备了CeO2掺杂的Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BNKT)陶瓷.XRD表明,在固相合成工艺中引入燃烧法制备BNKT陶瓷,比传统固相法降低预烧温度150 ℃,掺杂的CeO2扩散进入了BNKT钙钛矿的晶格,且当掺杂量为0%~0.3%时,形成纯的钙钛矿相结构;SEM表明,CeO2掺杂使晶粒尺寸趋于平均,对晶粒生长有抑制作用;介电温谱表明,随着CeO2掺杂量增加,介电常数εr和退极化温度Td、相转变温度Tm降低,介电反常峰逐渐弱化,且室温至300 ℃,介电损耗tanδ始终在0.3%以下,并从微结构缺陷空位形成机制角度,结合铁电畴壁运动状态,分析讨论了对材料介电特性的作用规律.     

Raman spectroscopy of Na0.5Bi0.5TiO3

We have measured the Raman spectra of bismuth sodium titanate in its rhombohedral, tetragonal, and cubic phases, with special attention paid to the phase transitions at 584K and 837K (heating). Both transitions appear to be order-disorder and strongly first order, with large thermal hysteresis. The phonon spectra at temperature slightly below the tetragonal phase are remarkably similar to BaTiO₃ with A₁(To) modes at 130, 269, and 541 cm^-1 (compared with 170, 270, 520 cm^-1 in BaTiO₃) and an E(TO) at 52 cm^-1.     

Characterization of multiferroic PbFe0.5Nb0.5O3 and PbFe0.5Ta0.5O3 ceramics derived from citrate polymeric precursors

Ceramics of the perovskite multiferroics PbFe_0.5Nb_0.5O₃ (PFN) and PbFe_0.5Ta_0.5O₃ (PFT) were synthesized from new citrate polymeric precursors. X-ray tests pointed to trace amounts of the pyrochlore phase. SEM studies revealed the heterogeneous grain size distribution for PFN and the homogeneous one for PFT. Dielectric studies pointed to one diffuse T-C phase transition at 378 K for PFN and two diffuse M-T and T-C phase transitions, at 200 and 235 K, for PFT, respectively. X-ray photoelectron spectroscopy studies of PFN reveal that all ions exist in one valence state, however, with two chemical shifts for Pb²⁺. Two valence states for the majority of ions of PFT seem to be connected with a higher volume fraction of the amorphous grain-boundary phase. The electronic energy band gap for both compounds is approximately 2.8 eV. Two magnetic transitions, ie, from the paramagnetic to the antiferromagnetic phase and then to the spin-glass phase, were observed at 156 and 10 K for PFN, and at 145 and 15 K for PFT, respectively.