BiFeO3薄膜的溶胶-凝胶制备及其铁电和介电性质

采用Bi(NO3)3.5H2O和Fe(NO3)3.9H2O为原料,用溶胶-凝胶方法在Pt/Ti/SiO2/Si制备了BiFeO3薄膜。XRD研究表明在500℃以上退火薄膜能够获得良好的结晶。铁电性测试结果表明450℃和500℃退火的薄膜铁电性相对较弱。在430 kV/cm的测试电场下,剩余极化分别为0.255μC/cm2和0.36μC/cm2。而550℃和600℃退火的薄膜的铁电性相对较强,在相同的测试电场下剩余极化强度分别为2.27μC/cm2和2.97μC/cm2。介电性研究表明450—550℃退火的薄膜具有小的介电色散和介电损耗,而600℃退火的薄膜则具有大的介电色散和介电损耗。     

底电极对BiFeO3薄膜电性质的影响

用溶胶-凝胶方法在LaNiO3,ITO和Pt底电极上制备了BiFeO3(BFO)薄膜.薄膜的退火温度为550℃.对不同底电极上的BFO薄膜的结构、形貌、铁电性、介电性和漏电流特性进行了研究.XRD研究表明不同底电极上的BFO薄膜呈不同的取向.所有的薄膜都没有观察到不纯相.剖面扫描电镜研究表明薄膜的厚度为350nm.铁电性测试表明在128kV/cm的测试电场下LaNiO3底电极上的薄膜的剩余极化强度最大,为3.31μC/cm2.而ITO和Pt底电极上的BFO薄膜的剩余极化强度分别为2.07μC/cm2与2.76μC/cm2.此外,漏电流的研究表明在ITO底电极上的BFO薄膜的漏电流最小.     

三明治结构薄膜的铁电性及蒙特卡罗算法模拟

用溶胶-凝胶方法在Pt/Ti/SiO2/Si衬底上制备了BaTiO3/BiFeO3/BaTiO3三明治结构薄膜。XRD测试结果表明薄膜由BaTiO3相和BiFeO3相构成。通过铁电性测量在薄膜中观察到了反铁电极化。对薄膜中存在的反铁电性进行了基于伊辛模型的蒙特卡罗模拟。模拟结果表明薄膜中的反铁电性来自不同铁电层之间的反铁电耦合。     

BaTiO3薄膜的Sol-Gel制备工艺及性能

利用溶胶－凝胶法（Sol-Gel)在Pt/Ti/SiO2/Si(100)衬底上制备了BaTiO3薄膜，研究了不同退火条件下BaTiO3薄膜的晶相结构及表面形貌，测试了BaTiO3薄膜的电学性能。发现经900℃、120min退火处理的BaTiO3薄膜的介电－温度（εr-T)关系具有明显的弥散相变特性。     

PZT/Fe3O4复合薄膜的制备及磁性和铁电性研究

用溶胶-凝胶方法制备了Pb（Zr0.5Ti0.5）O3-Fe3O4复合薄膜。XRD研究表明，Pb（Zr0.5Ti0.5）O3呈完全（100）取向，而Fe3O4颗粒则呈完全随机取向。在室温下探测到了共存的磁性和铁电性。铁电性测试结果表明，在9V的测试电压下，薄膜的Pr值为1．5／μc／cm^2。而磁性测量的结果表明，在1．5 T的外磁场作用下，薄膜的剩余磁化强度和饱和磁化强度分别为0．67emu／cm^3和3．5emu／cm^3。通过铁电材料Pb（Zr0.5Ti0.5）O3与磁性纳米Fe3O4粒子的复合获得了室温共存的铁电性和磁性。     

磁控溅射法La0.5Ca0.5MnxTi1-xO3薄膜的制备与结构研究

利用射频磁控溅射法结合后期热处理，在Si（100）基板上以不同的工艺条件成功制备了La0.5Ca
0.5MnxTi1-xO3（LCMTO）复铁电性磁电子薄膜.通过X射线衍射（XRD）、原子力显微镜（AFM）、电子衍射
能谱（EDS）等手段对薄膜进行了相的形成、结构特性及薄膜组成等的测试.研究表明，薄膜在600℃以上
开始析晶，850℃以上结晶完成,形成正交晶系钙钛矿相.硅基板上的LCMTO薄膜在不同温度下析出晶相的晶
格常数不同，温度越高，晶相的晶格常数越大；薄膜厚度越大，晶格常数相对较小;在薄膜制备时提高氧
分压，形成氧空位浓度低的完整晶相， Si基板上LCMTO薄膜的晶格常数相对较小.     

Sol-Gel法制备BST铁电薄膜及性能研究

采用溶胶-凝胶法在LaNiO3基底上制备了Ba0.5Sr0.5TiO3(BST)铁电薄膜。研究了不同退火温度对薄膜结晶性能的影响,并测试了各种BST薄膜的介电性能、铁电性能。实验结果表明经700℃退火处理的BST铁电薄膜具有比较优越的电性能,在测试频率为1 kHz时,700℃退火的BST薄膜的介电常数为384.1,介电损耗为0.018 6,在室温下外加偏压为1 V时,700℃退火的BST薄膜漏电流密度达到6.7×10-8A/cm2,其剩余极化强度和矫顽场分别为4.85μC/cm2和65.2 kV/cm。     

BiFeO_3薄膜的制备及掺杂改性研究进展

BiFeO3薄膜是当前多铁材料研究的热点之一。作为一种无铅多铁材料,BiFeO3薄膜优异的铁电和磁学性能使它在信息存储器、传感器和自旋电子器件等众多功能材料领域都有广阔的应用前景。但目前还存在漏电流较大及老化等一系列问题,使其与未来器件应用的要求还有一定差距。目前改善BiFeO3薄膜多铁性能的方法主要是通过改进制备工艺及掺杂改性。文章综述了BiFeO3薄膜近年的研究进展,介绍了其晶体结构及性能、制备工艺、掺杂改性,并展望了BiFeO3薄膜未来可能的研究方向和发展趋势。     

CoFe_2O_4/Ba_(0.8)Sr_(0.2)TiO_3异质结磁电复合薄膜的制备与多铁性能

利用射频磁控溅射法在Pt(200)/TiO_2/SiO_2/Si衬底上沉积CoFe_2O_4/Ba_(0.8)Sr_(0.2)TiO_3异质结层状磁电复合薄膜(Ba_(0.8)Sr_(0.2)TiO_3作为底层,CoFe_2O_4作为顶层)。X射线衍射表明CoFe_2O_4/Ba_(0.8)Sr_(0.2)TiO_3异质结复合薄膜是多晶的,由钙钛矿Ba_(0.8)Sr_(0.2)TiO_3相和尖晶石Co Fe2O4相组成。场发射扫描电镜表明在CoFe_2O_4薄膜和Ba_(0.8)Sr_(0.2)TiO_3薄膜之间有明显的界面。复合薄膜的介电常数随频率的变化关系显示了介电色散。复合薄膜表现为良好的铁电性和铁磁性共存。另外,复合薄膜具有直接的磁电耦合效应,磁电电压系数αE先随着偏置磁场Hdc的增大而增大,当偏置磁场Hdc增加到5.6 k Oe,复合薄膜达到最大的磁电电压系数,其值αE=8.7 m V/(cm·Oe),然后随着偏置磁场Hdc的进一步增大,磁电电压系数αE反而减小。     

SrTiO3基高压陶瓷电容器材料的组成与性能

研究了Ｂｉ２Ｏ３．３ＴｉＯ２和 ＰｂＴｉＯ３的加入量对ＳｒＴｉＯ３基高压陶瓷电容器材料性能的影响。实验的结果表明：最佳加入量的摩尔分数分别是Ｂｉ２ｏ３．３ｔＩｏ２为９％,ＰｂＴｉＯ３为１８％。在１２５０℃的温度下烧结获得了性能为：εｒ＝３２９５;Ｅｂ＝１０．２ｋＶ／ｍｍ;ｔｇδ＝６＊１０＾－４;△Ｃ／Ｃ（－２５－＋８５℃）≤±Ｓ     

Preparation and electrical properties of BaPbO3 thin film

BaPbO3 thin films were deposited on Al2O3 substrates by sol-gel spin-coating and rapid thermal annealing. The microstructure and phase of BaPbO3 thin films were determined by X-ray diffractometry, scanning electrons microscopy and energy dispersive X-ray spectrometry. The influence of annealing temperature and annealing time on sheet resistance of the thin films was investigated. The results show that heat treatment, including annealing temperature and time, causes notable change in molar ratio of Pb to Ba, resulting in the variations of sheet resistance. The variation of electrical properties demonstrates that the surface state of the film changes from two-dimensional behavior to three-dimensional behavior with the increase of film thickness. Crack-free BaPbO3 thin films with grain size of 90 nm can be obtained by a rapid thermal annealing at 700 ℃ for 10 min. And the BaPbO3 films with a thickness of 2.5 μm has a sheet resistance of 35 Ω·-1.     

Ferroelectric properties of Bi3.4Ho0.6Ti3O12 thin films prepared by sol-gel method

We have prepared the Ho-substituted bismuth titanate (Bi_3.4Ho_0.6Ti₃O₁₂, BHT) thin films on Pt/Ti/SiO₂/Si substrates using sol-gel method. The crystal structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The BHT film shows a single phase of Bi-layered Aurivillius structure and dense microstructure. The 2Pr and 2Ec of the 600-nm-thick BHT film were 38.4 μC/cm² and 376.1 kV/cm, respectively at applied electric field 500 kV/cm. The dielectric constant and dielectric loss are about 310 and 0.015 at a frequency of 1 MHz, respectively. The Pr value decreased to 93% of its pre-fatigue values after 4.46×10⁹ switching cycles at 1 MHz frenquency, and the BHT film shows good insulating behavior according to the test of leakage current. Supported by the Hubei Province Natural Science Foundation (Grant No. 2007ABA309)     

Preparation and properties of SrBi2.2 Ta2O9 thin film

SrBi_2.2 Ta₂O₉ (SBT) thin film with thickness of 2 μm was successfully prepared by sol-gel method, using strontium acetate semihydrate [Sr(CH₃ COO)₂ · 1/2H₂O] and bismth subnitrate [BiO(NO₃)], and tantalum ethoxide [Ta(OCH₂CH₃)₅] as source materials, glacial acetic and ethylene glycol as solvents. The X-ray diffraction (XRD) and transmission electron microscope(TEM) results indicate that SBT layer-perovskite phase obtained has to be single phase, SBT thin film is formed after being annealed at 800 °C for for 1 min. The typical hysteresis loop of SBT thin film on Pt/Ti/SiO₂/Si is obtained, and the measured polarization value of the SBT thin film is 4. 2 μ/C/cm². Foundation item: Project (HIT. 2001. 67) supported by the Scientific Research Foundation of Harbin Institute of Technology; project (50172012) supported by the National Natural Science Foundation of China     

Dielectric properties of Pb (Zn1/3 Nb2/3) O3?PbZrO3?PbTiO3 solid solution near morphotropic phase boundary

The dielectric properties of Pb(Zn_1/3Nb_2/3) O₃-PbZrO₃−PbTiO₃ (PZN-PZ-PT) system near the rhombohedral/tetragonal morphotropic phase boundary (MPB) are carefully studied in this paper. It is found that, for all samples, the curves around the temperatures of dielectric permittivity peak show the characteristics of diffuse phase transition. The change in PbZrO₃/PbTiO₃ ratio has much influence on the dielectric properties of the samples. The extent of diffuse phase transition increases with the increasing Zr/Ti ratio. The samples in rhombohedral region have typical diffuse phase transition in the temperature range measured. However, for the samples with tetragonal symmetry, a spontaneous normal ferroelectric-relaxor phase transition exists at temperature lower than that of permittivity peak. This normal ferroelectric-relaxor phase transition is confirmed by the experiment of thermally driven current. The analysis of TEM reveals that the samples in tetragonal region show a 90% macrodomain structure, while the samples in rhombohedral region have the configuration of microdomain structure.     

不同微观形貌的ZnO薄膜的制备及其表征

通过溶胶凝胶法在透明玻璃上制备了ZnO薄膜,分别采用XRD、SEM和AFM等分析方法对所制样品进行表征,分析了样品的结构特性。研究了络合剂及添加剂等因素对ZnO薄膜微观形貌的影响,并且考察了不同计量比下ZnO颗粒的富集程度、纳米线的对称程度差别,得到了致密粒子(0.7μm)和纳米线(0.5μm)的两种微观结构ZnO薄膜。研究表明,纳米线呈倒伏状分布在基体表面,并分析了对称分布的纳米线结构产生的机理。     

新型钾基四方钨青铜结构化合物K3La3Ti2Nb8O30

根据四方钨青铜结构稳定性的晶体化学原理,设计了新型的钾基四方钨青铜结构化合物K₃La₃Ti₂Nb₈O₃₀,并采用固相反应法对其进行了制备。采用X射线衍射仪表征其物相,发现除了少量杂相存在外,其主相可以确认为目标化合物, 并采用扫描电子显微镜和能谱仪对其微观形貌和微观区域元素成分进行分析。使用精密阻抗分析仪对其不同频率下的介电温谱进行测量（20~600 ℃）,结合结构容忍因子及A位离子平均半径所进行的预测结果,显示该化合物在室温（20 ℃）以下可能具有弛豫铁电性。     

Microstructures and magnetic properties of [SiO2/FePt]5/Ag thin films

[SiO2/FePt]5/Ag thin films were deposited by RF magnetron sputtering on the glass substrates and post annealing at 550 ℃ for 30 min in vacuum. Vibrating sample magnetometer and X-ray diffraction analyser were applied to study the magnetic properties and microstructures of the films. The results show that without Ag underlayer [SiO2/FePt]5 films deposited onto the glass are FCC disordered; with the addition of Ag underlayer [SiO]FePt]5/Ag films are changed into L10 and （111） mixed texture. The variation of the SiO2 nonmagnetic layer thickness in [SiO2/FePt]5/Ag films indicates that SiO2-doping plays an important role in improving the order parameter and the perpendicular magnetic anisotropy, and reducing the grain size and intergrain interactions. By controlling SiO2 thickness the highly perpendicular magnetic anisotropy can be obtained in the [SiO2 （0.6 nm）/FePt （3 nm）]5/Ag （50 nm） films and highly （001）-oriented films can be obtained in the [SiO2 （2 nm）/FePt （3 nm）]5/Ag （50 nm） films.