Ba0.9Sr0.1TiO3薄膜的椭偏光谱研究

用椭偏光谱仪首次在光子能量为2．1－5．2eV的范围内,测量了不同热处理温度下Ba0.9Sr0.1TiO3(BST)薄膜的椭偏光谱。建立适当的拟合模型,并用Cauchy色散模型描述BST薄膜的光学性质,用最优化法获得了所用样品的光学常数（折射率n和消光系数k）谱及禁带能Eg比较这些结果,初步得到了BST薄膜的折射率n、消光系数k和禁带能Eg随退火温度变化的变化规律。     

改进sol-gel技术BST薄膜的制备及性能研究

为了制备高性能BST薄膜,采用改进的溶胶 凝胶(sol gel)方法在Pt/Ti/SiO2/Si基片上制备出了不同结构、不同组成的BST薄膜;研究了BST薄膜的微观结构及其介电、铁电性能。XRD分析表明,当热处理温度为750℃时,得到完整钙钛矿结构的薄膜材料。SEM电镜显示,含种子层的Ⅱ、Ⅲ、Ⅳ3种不同类型的BST薄膜的结晶状况有很大改善。得到的BST20薄膜的介电峰温区覆盖常温段,介电常数为405,介电损耗为0.011,剩余极化强度为Pr=2.3μC·cm-2,矫顽场为Ec=45kV/cm。     

氧退火对SiO2/Si衬底BST薄膜特性的影响

利用氩离子束镀膜技术和硅平面工艺在经过干氧氧化的硅衬底上制备一层钛酸锶钡薄膜 ,并在氧气中进行不同条件的退火处理 ,然后蒸铝及利用光刻技术制作铝电极而形成 MIOS电容结构 ,研究其物理及电学特性。结果表明 ,氧退火条件对衬底的钛酸锶钡薄膜的物理及电学特性有较为明显的影响。     

Effect of excess TiO2 on the phase evolution and densification of sol-gel derived (Ba,Sr)TiO3 powders

Nanoscaled (Ba_2/3Sr_1/3)Ti_{1 + x} O₃ powders have been prepared by sol-gel technique. Their phase evolution and densification behaviors have been studied by differential thermal analysis (DTA) and high temperature dilatometer, respectively. It is found the addition of 2 mol%-excess amount of TiO₂ lowers the activation energy required for the formation of the perovskite phase by about 130 kJ/mol and thus lowers the crystallization temperature of BST powders. However, the excess amount of TiO₂ makes the nano-powder difficult to sinter. Transmission electron microscopy reveals that a metastable nano-porous layer has formed on the surface of TiO₂-excess nanopowder and this may account for the slow densification rate.     

(Ba0.5Sr0.5)TiO3/LaNiO3异质薄膜的介电调谐特性

用脉冲激光沉积工艺制备Ba0.5Sr0.5TiO3(简称BST)薄膜和Ba0.5Sr0.5TiO3/LaNiO3(简称BST/LNO)薄膜。在650℃原位退火10 min,获得了(100)和(110)择优取向生长的BST和BST/LNO薄膜,薄膜晶粒呈柱状结构,BST薄膜和BST/LNO异质结构薄膜的晶粒尺寸分别为150~200 nm和50~80 nm。在室温和1 MHz条件下,BST薄膜和BST/LNO异质结构薄膜的相对介电常数和介电调谐率分别达811和58.9%、986和60.1%;用LNO作底电极,可增益介电常数和介电调谐率。     

铁电薄膜移相器研究进展

铁电薄膜移相器响应速度快、成本低、功耗和体积小,是一种模拟移相器,非常适合应用于相控阵天线特别是共形阵天线.介绍了4种主要的铁电薄膜移相器的结构、原理、性能和特点,指出分布型和全通网络型铁电薄膜移相器具有良好的发展前景,并进一步总结了国内外研究现状和存在的问题,提出了今后的研究方向.     

Boosting dielectric temperature stability in BNBST-based energy storage ceramics by Nb2O5 modification

Exploring environment-friendly energy storage ceramics simultaneously featuring large recoverable energy storage density (W_rec), high-energy storage efficiency (ƞ), and excellent temperature stability is highly desirable for the application of pulsed power systems. Herein, Nb₂O₅ was introduced to modify BNBST-based lead-free relaxor ferroelectric ceramics in an effort to enhance the dielectric temperature stability. (Bi_0.5Na_0.5)_0.65(Ba_0.3Sr_0.7)_0.35(Ti_0.98Ce_0.02)O₃ (BNBSTC) + x wt%Nb₂O₅ (0 ≤ x ≤ 4) ceramics were prepared by a solid-state reaction method. The phase structure, microstructure, dielectric, and energy storage properties of the ceramics have been systematically studied. It was found that the ε_r–T curve was flattened, and the dielectric temperature stability was effectively improved due to the addition of Nb₂O₅. A noticeable W_rec (1.44 J/cm³) with high η (84.1%) was obtained in BNBSTC + 2 wt%Nb₂O₅ ceramics at a low electric field of 90 kV/cm, which was mainly due to a refined P–E loop induced by Nb₂O₅. In addition to excellent frequency and anti-fatigue cycle stability, this ceramic provides a new solution for designing pulsed power capacitors with high energy density and high temperature stability under low voltage driving conditions.     

两步加压法制备高介电调谐率的Ba_(0.6)Sr_(0.4)TiO_3厚膜

在传统的丝网印刷厚膜制备工艺中增加了两步加压预处理流程,采用这种新方法制备了致密的Ba0.6Sr0.4TiO3(BST)厚膜,并系统地研究了两步加压法对BST厚膜微结构和介电性能的影响。结果表明,与传统工艺相比,两步加压法可使BST厚膜获得更致密的微结构和更高的介电调谐率。在20℃和10kHz环境下,厚膜的介电常数和介电损耗分别为958和0.013 4,6kV/mm偏场下介电调谐率和优值分别为48.6%和36.3。     

微波调谐铈钇共掺Ba0.6Sr0.4TiO3薄膜的改性机制研究

用改进的溶胶一凝胶法制备光滑致密的预晶化铈（Ce）和锰（Mn）共掺钛酸锶钡（CeMn—SST）薄膜。电容－电压曲线表明,随着薄膜厚度的增加,综合介电性能大幅度改善,8层薄膜显示介电常数约为1300、低于0．007介电损耗、高于58％调谐率及接近180优质因子等优化介电性能,为主要沿（1101晶面层状生长的钙钛矿结构。     

Energy storage properties and transparency in (Ba0.6Sr0.4)1-1.5xBixTi1-x(Mg1/3Nb2/3)xO3 ceramics

Fully densified (transparent) ceramic with small grain size is highly desired to improve the field breakdown strength (BDS) and its scattering. Sintering behavior, microstructural evolution, electric, dielectric, and energy storage properties of (Ba_0.6Sr_0.4)_1-1.5xBi_xTi_1-x(Mg_1/3Nb_2/3)_xO₃ (x = .04–.10) ceramics have been studied in this paper. Phase pure cubic perovskite is observed for the x = .04 composition. Nb-rich tungsten bronze type and Ti-rich barium titanate secondary phases are present in the x > .05 compositions. A multiphasic transparent ferroelectric ceramic with ∼74.2% (780 nm) transmittance and a high refractive index of ∼2.3 within the visible region could be successfully obtained for the x = .10 composition by traditional ceramic process. The x = .09 composition demonstrates good energy storage performance (recoverable energy density W_rec = 3.74J/cm³, efficiency η = 77% and BDS = 390kV/cm) with extremely low scattering in BDS, suggesting potential application in large sized energy storage capacitor.