Improved electric properties in BiFeO3 films by the doping of Ti

We prepared BiFe_1−x Ti _x O_3+δ (BFTO) films by sol gel process and various oriented films were deposited on LaNiO₃ coated SiO₂/Si substrates with different x. The effects of Ti substitution on dielectric, ferroelectric, magnetic and leakage conduction properties in BFTO system have been studied. Enhanced ferroelectricity was observed at room temperature due to the substitution of Ti. The largest double remnant polarization of 3.8 μC/cm² was acquired in the film with x = 0.10. Further more, it was observed that the dielectric constants were also enhanced by the substitution of Ti. The film with x = 0.10 has the largest dielectric constant below 100 kHz and Debye-like relaxation were observed in the films with x = 0.05 and 0.10. The leakage conduction was reduced with the increasing of the content of Ti. More over, the magnetism was also altered by the substitution.     

纳米晶钛酸钡的介电性能

采用硬脂酸凝胶法制备了纳米晶BaTiO3,用差热热重分析、红外光谱分析、X射线衍射分析等手段对产物的形成过程、晶型、粒径进行了分析.通过对材料介电性能的研究发现,纳米材料的静态介电常数远大于常规材料的介电常数,随着粒径的减小,纳米材料的介电常数先增大而后有所降低.随着环境湿度的升高,纳米晶材料的介电常数逐渐增大,在高湿度条件下,其介电常数与湿度成线性关系.     

溶胶-凝胶法制备甲烷部分氧化制合成气用催化剂

用溶胶－凝胶法制备了一系列ＮｉＯ／γ－Ａｌ２Ｏ３催化剂，应用低温氮吸附，ＸＲＤ和ＴＰＲ等物理化学方法表征了这种新材料的结构和物化性能。结果表明，由于载体与活性组分间的强相互作用，使溶胶－凝胶法制备的催化剂具有粒度小，活性组分在载体表面均一高分散和热稳定性好等特点，同时，考察了该催化剂上甲烷部分氧化制合成气的反应性能，发现当Ｎｉ含量适当时，可获得高的反应活性和选择性。     

Beiträge zu den Eigenschaften von Titanaten mit Ilmenitstruktur. I. Aspekte eines Hochtemperaturphasenübergangs in NiTiO3

Contributions to the Properties of Titanates with Ilmenite Structure. I. Aspects of a High Temperature Phase Transition in NiTiO₃ NiTiO₃ (Ilmenite structure) shows an anomalous increase of the electrical conductivity in the temperature range between 1 250°C and 1 290°C. The temperature dependence of the Seebeck coefficient is also found to be anomalous in this region. DTA experiments are consistent with a phase transition; the transition enthalpy was estimated to Δ_uH_m = 17 ± 3 kJmol^?1. NiTiO₃ powders and single crystals were quenched from 1 350°C and 1 200°C to room temperature; in principle no differences of the lattice parameters or atomic positions could be detected. The determination of the distribution of cations using x-ray powder methods failt because of strong texture effects. Structure refinements with single crystal methods suggest an ordered Ilmenite structure independent of the quenching temperature. The results are in agreement with a reversible order-disorder transition of higher order. It seems to be impossible to quench the high temperature phase by conventional methods.     

Ca改性钛酸铅纳米晶的制备及结构研究

用溶胶-凝胶工艺制备了Pb_1-xCa_xTiO₃(0≤x≤0.3)纳米晶,在不同焙烧条件下研究其粉体晶相结构的变化.研究结果表明,升温速度和焙烧温度对纳米粉的晶相、晶胞参数和晶粒尺寸有显著影响.讨论了晶胞参数、四方畸变度和晶胞体积与Ca含量的关系.     

溶胶—凝胶法合成LaCr1—xFexO3超细粉末

以无机盐为原料，用溶胶－凝胶法合成了ＬａＣｒ１－ｘＦｅｘＯ３超细粉末，其平均粒径〈１３０ｎｍ。研究表明，随着焙烧温度的升高或时间的增加，粉末的粒径随之增大，比表面积则随之减小；ＬａＣｒ１－ｘＦｅｘＯ３粉末为钙钛矿型结构，其晶胞参数随着Ｆｅ含量的增加而增大。     

Electrocatalytic Oxidation of Sulfur Containing Amino Acids at Renewable Ni‐Powder Doped Carbon Ceramic Electrode: Application to Amperometric Detection L‐Cystine,L‐Cysteine and L‐Methionine

A sol‐gel technique was used here to prepare a renewable carbon ceramic electrode modified with nickel powder. Cyclic voltammograms of the resulting modified electrode show stable and a well defined redox couple due to Ni(II)/Ni(III) system with surface confined characteristics. The modified electrode shows excellent catalytic activity toward L ‐cystine, L ‐cysteine and L ‐methionine oxidation at reduced overpotential in alkaline solutions. In addition the antifouling properties at the modified electrode toward the above analytes and their oxidation products increases the reproducibility of results. L ‐cystine, L ‐cysteine and L ‐methionine were determined chronoamperometricaly at the surface of this modified electrode at pH range 9–13. Under the optimized conditions the calibration curves are linear in the concentration range 1–450 μM, 2–90 μM and 0.2–75 μM for L ‐cystine, L ‐methionine and L ‐cysteine determination, respectively. The detection limit and sensitivity were 0.64 μM, 3.8 nA/ μM for L ‐cystine, 2 μM, 5.6 nA/ μM for L ‐methionine and 0.2 μM and 8.1 nA/μM for L ‐cysteine. The advantageous of this modified electrode is high response, good stability and reproducibility, excellent catalytic activity for oxidation inert molecules at reduced overpotential and possibility of regeneration of the electrode surface by potential cycling for 5 minutes. Furthermore, the modified electrode has been prepared without using specific reagents. This sensor can be used as an amperometric detector for disulfides detection in chromatographic or flow systems.     

YAG:Eu3+、Bi3+的溶胶-凝胶法合成及其结构和发光性能

溶胶-凝胶法以其各组分混合均匀性好、反应温度低、节省能源等诸多优点而引起了人们极大兴趣[1,2].近年来,利用该法研制玻璃和陶瓷等无机材料的报道越来越多[3,4].     

非水体系中电解镍中间产物制备纳米NiO

采用纯镍为阳极,乙酰丙酮和乙醇的混合溶液中加入少量有机胺导电盐为电解液,施加一定电流使镍溶解,然后将电解液直接水解,控制一定的水解条件,制备得到纳米NiO粉体. 采用拉曼光谱、红外光谱、元素分析、XRD 和TEM 分别对电解得到的纳米NiO前驱体和纳米NiO进行了分析与表征, 并探讨了电化学溶解镍金属法制备纳米NiO反应的影响因素.电化学溶解镍金属得到的前驱体为Ni(OEt)2(acac)2,这种不溶性镍醇盐配合物升温至40～50℃即可溶解于乙醇溶液中,可直接应用于溶胶 凝胶(Sol gel)过程.水解后的纳米NiO呈无定形结构, 350 ℃煅烧后形成立方晶型NaCl结构, 纳米NiO经600 ℃煅烧后粒径分布在5～10 nm. 该方法理论上为二价不溶性金属醇盐经溶胶 凝胶工艺制备纳米氧化物材料提供了一条新的途径.     

Effects of Cerium Doping at Ti Sites and Europium Doping at Ba Sites on Dielectric Properties of BaTiO3 Ceramics

IntroductionBarium titanate(BaTiO3or BT) is widely used asa capacitor material, because it is a simple compoundwith the highest permittivity. The dielectric constant atroom temperature is about 1600 for BaTiO3polycrys-tals[1]. However, barium titanate as …     

YAG∶Eu~(3+)、Bi~(3+)的溶胶-凝胶法合成及其结构和发光性能

溶胶－凝胶法以其各组分混合均匀性好、反应温度低、节省能源等诸多优点而引起了人们极大兴趣［１，２］．近年来，利用该法研制玻璃和陶瓷等无机材料的报道越来越多［３，４］．但研制稀土固体发光材料的报道则较少．钇铝石榴石Ｙ３Ａｌ５Ｏ１２（ＹＡＧ）是一种很好的基...     

Electrochemical Sensor for Sulfite and Sulfur Dioxide Based on 3‐Aminopropyltrimethoxysilane Derived Sol‐Gel Composite Electrode

A new sol‐gel derived composite sensor has been developed for the determination of sulfite and sulfur dioxide using 3‐aminopropyltrimethoxysilane, ferrous sulfate and graphite powder by sol‐gel process. Cyclic voltammetry and amperometry studies revealed that the modified iron dispersed sol‐gel derived ceramic composite electrode exhibited excellent characteristics for the electrocatalytic oxidation of sulfite at a reduced potential of +0.35 V with good sensitivity and selectivity. The pH and the potential for sulfite estimation have been optimized. The sensor exhibited rapid and linear response to sulfite in the concentration range from 0.73 mg/L to 95.42 mg/L with a correlation coefficient of 0.997. The proposed sensor can be utilized for the determination sulfur dioxide after absorbing in a suitable medium and has promising characteristics such as, rapid response, good reproducibility and remarkable stability.     

基于溶胶-凝胶技术可更新的安培分析免疫传感器用于人血清中补体3的测定

在低温下,通过混合石墨粉,补体3抗血清,溶胶－凝胶而制备了一种基于啼－凝胶技术的可更新的安培分析免疫传感器。该传感器坚固,多孔,拥有一个更新的表面,在辣根过氧化物酶标记的补体3的协助下,通过竞争性的免疫分析来确定人血清中补体3的含量。以邻－氨酚作为底物,－150mV作为工作电位,响应电流与补体3的浓度在1．17－35．1μg/mL范围内呈线性关系,检出限为0．56μg/mL。分析血清样本结果表明所制备的传感器在临床分析中是可行的。