热压法制备P型Bi2Te3基温差电材料研究

以P型赝二元Bi2Te3-Sb2Te3体系温差电材料区熔晶棒为前驱体,采用真空热压烧结法制备材料样品。测试热压前后材料样品性能,测试结果表明:热压样品较区熔材料具有更高的致密度和机械强度,改善了Bi2Te3基温差电材料易沿解理面发生劈裂的现象;同时,热压工艺促使了材料内部晶体结构和载流子浓度的变化,引起材料电导率的降低和塞贝克系数的改变,导致材料热导率显著降低。综合考虑材料各项性能参数,热压材料的热电优值基本与区熔材料相当,但前者的力学强度明显优于后者,在实际使用中将占有明显的优势。     

Bi4Ti3O12铁电薄膜的制备及研究进展

铁电薄膜具有良好的铁电、介电性能,在非挥发存储器件方面有很好的应用前景.本文介绍了钛酸铋(Bi4Ti3O12)铁电薄膜的研究现状,对目前Bi4Ti3O12铁电薄膜最常用的几种主要制备方法及其掺杂改性进行了评述,指出了Bi4Ti3O12铁电薄膜研究中亟待解决的几个问题.     

原位反应合成法制备AgSnO2Bi2O3电接触材料及其性能研究

以熔炼-雾化法合成AgSnBi合金粉体为原料,采用原位反应合成法制取AgSnO_2Bi_2O_3中间体粉体;采用粉末冶金技术制备了AgSnO_2Bi_2O_3电接触材料,重点探究了成型压力、烧结温度等对其物理性能及断口微观组织的影响规律。采用扫描电子显微镜(SEM)、X-ray衍射分析仪(XRD)、电导率仪、维氏硬度计等对AgSnO_2Bi_2O_3电接触材料的微观形貌、物相组成及物理性能进行相应的表征。研究结果表明:熔炼-雾化法制得的AgSnBi合金粉体形貌上呈球状及棒状颗粒,平均颗粒尺寸为10～20μm。AgSnBi合金粉体氧化前的物相主要由Sn、Ag4Sn、Ag3Sn及Bi相构成;随着氧化温度的升高,AgSnBi合金粉体的氧化增重量先快速增加而后趋于稳定,并于800℃、2 h条件下实现完全氧化。由物理性能关系曲线分析得出在成型压力1200 MPa、烧结温度920℃、颗粒粒径400目条件下,AgSnO_2Bi_2O_3电接触材料的电阻率、硬度及密度达到最佳值,分别为2.32μΩ·cm、78.2 HV0.5与9.352 g/cm3。由微结构分析得出AgSnO_2Bi_2O_3电接触材料自然断口表面不存在明显的韧窝带,其断裂类型判定为脆性断裂。     

电沉积CuInSe2(CIS)薄膜材料的组成与形貌

采用乙醇为溶剂.通过恒电流的方法电沉积制备了CuOnSe2薄膜材料,研究了制备工艺条件对材料组成、结构与性能的影响,研究结果表明:最佳的沉积电流为-2 mA(vs.SCE),且电流密度的增加有利于电位较负元素的沉积;沉积膜中元素的原子比与电解液中的浓度比变化一致;硒化退火是获得高质量黄铜矿结构CuInSe2薄膜的必要过程,随着退火温度的升高和退火时间的延长,CuInSe2薄膜退火后结晶程度变好,颗粒变大,致密性也有所改善.     

Bi2Te3基温差发电组件的热应力和结构参数选择

温差电材料性能决定了温差发电组件(TEM)的发电功率及转换效率,而在使用过程中由于环境因素的影响,对其机械性能也提出了一定的要求.热压法制备的Bi2Te3基温差电材料密度和强度均有提高,缓解了区熔法制备的Bi2Te3基温差电材料在平行于晶体方向上易发生解理破坏的问题,但还不能完全避免.通过分析Bi2Te3基温差电材料沿...     

添加物Bi2O3对触头材料AgSnO2的显微组织影响

本文利用扫描电镜及能谱分析,对添加Ｖｉ２Ｏ３的ＡｇＳｎＯ２触头材料经电弧作用后的表面及内部显微组织进行了较为详细的分析。结果表明：经电弧作用后,由于Ｂｉ２Ｏ３改善了Ａｇ对ＳｎＯ２颗粒的湿润性,使得熔化区（直径约０．３ｍｍ、深约１．２ｍｍ）内氧化物颗粒重新分布而形成类似由网络连接的“细胞”状组织,而非聚集于触头表面。其中“细胞”边界主要由ＳｎＯ２颗粒聚集而成,内部由Ａｇ与少量氧化物构成,细胞尺寸约为     

共沉积法AgFe2O3电接触材料的组织与性能研究

采用共沉积工艺制备了AgFe2O3电接触材料。用X射线衍射、金相显微镜等观察了材料的相组成及显微组织,测量了材料的密度、硬度、电导率等性能。结果表明,采用共沉积工艺制备的AgFe2O3电接触材料组织均匀,电阻率为2．1μΩ．cm,密度为9．6g／cm^3。     

氢气泡模板法电沉积La-Ni合金薄膜电极

在强阴极极化下,以析出的氢气泡为模板,电沉积制备了La-Ni贮氢合金薄膜电极。采用扫描电子显微镜(SEM)及X射线衍射仪(XRD)对合金薄膜电极的表面形态和结构进行了表征;以循环伏安、恒电流充放电实验考察了合金薄膜电极的电化学行为。结果表明,合金薄膜电极含La Ni5相,电化学吸放氢性能好,最高电化学放电比容量达286 m Ah/g,无需活化过程,首次充放电即可达到最高放电容量,作为氢镍电池的负极,在1.2 V附近有一个平稳的放电平台。     

Bi掺杂AgSnO2（12）电接触材料的制备及性能研究

将采用化学沉淀法制备的Bi掺杂量为25%(原子分数)的SnO2纳米颗粒(Sn0.75Bi0.25O2)作为增强相,借助于粉末冶金法制备了AgSnO2(12)电接触材料,分析了Bi元素掺杂对电接触材料性能的影响。试验结果表明,Sn0.75Bi0.25O2纳米颗粒增强的AgSnO2(12)电接触材料组织结构均匀,密度、硬度高,导电性好。电性能试验表明,Sn0.75Bi0.25O2纳米颗粒增强材料的燃弧时间短、能量低,接触电阻低且稳定,抗电弧侵蚀能力强。     

电沉积PbO_2电极的析氧行为

本文探讨了PbO_2电极的电沉积制备条件以及电极的析氧行为和稳定性。实验结果表明:FcCL_3R的存在可以显著提高电沉积PbO_2电极的析氧性能,提高电极在强氧化性条件下的稳定性。从电沉积层的组成、Fe_2O_3、Pb_2和TiO_2的晶体结构以及不同条件下PbO_2电极的析氧催化行为角度对上述结果进行了理论探讨。     

Micro-structure and ferroelectric properties of BiFeO3 thin films formed on Pt-coated r-plane sapphire substrates

Magnetoelectric BiFeO₃ (BFO) materials exhibit ferroelectric and ferromagnetic properties simultaneously, therefore they have a potential to be applied in magnetic as well as ferroelectric devices. BFO thin films were formed by depositing sol-gel solutions on Pt-coated r-plane sapphire dielectric substrates. We did not observe any secondary phase such as Bi₂Fe₄O₉ on the r-plane sapphire substrates, which is generally observed on Si substrates. We observed small ferroelectric grains of about 0.1 μm on Pt/sapphire structures. The leakage current density in BFO films was found to be decreased dramatically after optimizing process conditions of stoichiometric BFO chemical solution. The leakage current densities were in the range of 10^{− 7} A/cm² at room temperature and 10^{− 9} A/cm² at 80 K under 0.4 MV/cm applied electric field. The main reason for low leakage current is considered to be reduction of oxygen vacancies due to the presence of exclusive Fe^{3 +} valance state in the films. An applied electric field higher than 0.5 MV/cm was required to pole the BFO films, which made it difficult to obtain the saturated polarization at room temperature. We could measure the saturated remanent polarization in the BFO films at 80 K and the obtained remanent polarization was 100 μC/cm².     

Growth and electrical properties of (211) BaTiO3 thin films on Pt-coated Si(100) substrates

Abstract

Barium titanate (BaTiO₃) thin films with high (211) orientation have been prepared on Pt(111)/Si(100) substrates by R. F. magnetron sputtering at a substrate temperature between 550°C and 580°C in an Ar/O₂ atmosphere. The I-V curve of a thin film capacitor (Ag-BaTiO_3-Pt) has been measured and the C-V curves are obtained for frequencies between 100Hz and 1MHz. Neither the I-V curve nor the C-V curves are symmetrical and a very large change in the slope of all curves is found to occur at ～+0.5v.     

V2O5含量对Bi2O3-V2O5复合添加NiCuZn铁氧体性能的影响

用传统陶瓷工艺制配了(Ni0.16Cu0.2Zn0.64O)1.02(Fe2O3)0.98铁氧体材料,研究了Bi2O3-V2O5复合添加对材料烧结特性和磁性能的影响.结果表明,复合添加bi2O3-V2O5能促进样品致密化、提高起始磁导率和品质因数.当添加0.3wt%Bi2O3、0.15wt%V2O5时,930℃烧结起始磁导率μi＞800、品质因数(94)、密度(5.12 g/cm3)都达到较大值,比同样配方只掺杂Bi2O3的NiCuZn材料明显提高.     

Mocvd growth and characterization of PbTiO3 thin films on Pt/Ti/SiO2/Si substrates

Abstract

PbTiO₃ thin films were grown by Metalorganic Chemical Vapor Deposition (MOCVD) on 6′′ platinized Si wafers. In a first stage of investigation, the quality of the platinum surface was correlated with the substrate temperature and the composition of the atmosphere of the warming-up procedure in the reactor. The Pt reflectivity and the surface roughness were clearly modified by higher temperatures and by oxygen environments, though no clear diffusion mechanisms could be observed with Auger. In a second stage of investigation, the growth of PbTiO₃ was studied. Using a standard PbTiO₃ growth procedure, we studied the influence of substrate temperature and gas phase composition. Below 650°C, PbO appears as the main phase; at 650°C, PbTiO₃ and PbO coexist; and at 700°C, only PbTiO₃ is detected. The morphologies were examined by SEM / AFM and the roughness at the interface was studied by ellipsometry.     

Structural properties and dopant-modified bandgap energies of Ba0.5 Sr 0.5 TiO 3 thin films grown on LaAlO 3 substrates

Ba_0.5Sr_0.5TiO₃ thin films doped with different concentration of Ti, Mg and Al dopants were prepared by pulsed laser deposition technique on LaAlO₃ substrates. The crystalline properties of these doped thin films were studied using X-ray diffraction, micro-Raman scattering, atomic force microscopy, and transmission electron microscopy. The bandgap energies of BST thin films are determined from the transmission and absorption measurements by the ultraviolet-visible spectrophotometer. It was found out that the bandgap energies of the doped BST thin films depend strongly on the dopant concentration.     

Growth and characterization of non-c-axis-oriented SrBi2Ta2O9 epitaxial thin films on Si(100) substrates with SrRuO3 bottom electrodes

Abstract

We have successfully grown non-c-axis-oriented epitaxial ferroelectric SrBi₂Ta₂O₉ (SBT) films with (116) and (103) orientations on Si(100) substrates using epitaxial (110)- and (111)-oriented SrRuO₃ (SRO) bottom electrodes, respectively. The SRO orientations have been induced by coating the Si(100) substrates with epitaxial YSZ(100) and MgO(111)/ YSZ(100) buffer layers, respectively. All films were sequentially grown by pulsed laser deposition. Specific in-plane orientations of the epitaxial SBT films were found, which are in turn determined by specific in-plane orientations of the epitaxial SRO bottom electrodes. These include a diagonal rectangle-on-cube epitaxy of SRO(110) on YSZ(100) and a triangle-on-triangle epitaxy of SRO(111) on MgO(111).     

Oriented growth of Bi3.25La0.75Ti3O12 thin films on RuO2/SiO2/Si substrates by using the polymeric precursor method: Structural, microstructural and electrical properties

c-axis oriented Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films were grown on a RuO₂ top electrode deposited on a (100) SiO₂/Si substrate by the polymeric precursor method. X-ray diffraction and atomic force microscope investigations indicate that the films exhibit a dense, well crystallized microstructure having random orientations with a rather smooth surface morphology. The electrical properties of preferred oriented Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films deposited on RuO₂ bottom electrode leaded to a large remnant polarization (P _r ) of 17.2 μC/cm² and (V _c ) of 1.8 V, fatigue free characteristics up to 10¹⁰ switching cycles and a current density of 2.2 μA/cm² at 5 V. We found that the polarization loss is insignificant with nine write/read voltages at a waiting time of 10,000 s. Independently of the applied electric field the retained switchable polarization approached a nearly steady-state value after a retention time of 10 s.     

Electrically tunable Ag(Ta,Nb)O3 thin film structures on oxide substrates

Abstract

We report on design, fabrication, and comparative test of three different types of voltage-variable interdigital capacitors made on ferroelectric Ag(Ta,Nb)O₃ films deposited on MgO and A1₂O₃ substrates. X-ray diffraction patterns show that ATN films pulsed laser deposited on MgO(001) and Al₂O₃(0112) single crystals have preferential (00/) and (0kk) orientation. Capacitance and loss tangent in interdigital capacitors were measured as the functions of frequency and applied dc voltage bias. Loss tangent was as low as 0.0025 and 0.0034 and AT-factor (tunability/tanδ) was around 26.2 and 20.0 for MgO and A1₂O₃, respectively, @ ± 40 V (maximum electric field 200 kV/cm), 300 K, and 1 MHz. Both of polarization and steady leakage currents were observed in the current-time domain measurements. 0.1 pF interdigital capacitors have pA leakage current level @ ± 40 V.     

Laser ablation preparation and property of bismuth-layer-structured SrBi2Ta2Ta2O9 and Bi4Ti3O12 ferroelectric thin films

Abstract

Bismuth-layer-structured ferroelectric thin films, SrBi₂Ta₂O₉ and Bi₄Ti₃O₁₂, have been prepared by laser ablation method on both Pt sheets and Si wafers at low temperatures of 400 ～ 500°C. These thin films have been characterized by XRD, XPS, AFM, C-V, D-E hysteresis and J-V measurement. SrBi₂Ta₂O₉ thin films have a good (105) preferential orientation, and Bi₄Ti₃O₁₂ thin films have (117) and c-axis orientation on these substrates. Ferroelectric film-SiO₂-Si structures show good C-V hysteresis curve owing to Si surface potential controlled by the D-E hysteresis. D-E hysteresis is obtained in Bi₄Ti₃O₁₂ thin film prepared on Pt sheet, and the remnant polarization and the coercive force are 7.5 μC/cm² and 72 kV/cm, respectively.