Li和Nb共掺NiO的巨介电性质研究

以溶胶-凝胶法制备了化学式为LixNbyNi1-x-yO的NiO基巨介电陶瓷材料,研究了其在室温下的介电性质。在室温下,陶瓷材料频率从100Hz～10MHz内,得到了接近105数量级的相对介电常数;在掺杂材料中,Nb含量对陶瓷材料的介电性质具有显著的影响,其介电常数随着Nb含量的增加而明显减小。通过XRD、SEM以及EDS对陶瓷相成分和形貌的分析结果表明,陶瓷材料的巨介电性质归因于其具有半导性晶粒和绝缘晶界结构的内部边界层电容器模型。     

High dielectric permittivity of Li and Sc co-doped NiO ceramics

Microstructures, phase structures, and dielectric properties of Li and Sc co-doped NiO ceramics were systematically investigated. A high ε′ (~10⁴) is observed in a wide temperature (200–420 K) and frequency (100–10 kHz) range. The increase of ε′ with Li concentration is related to the increase of grain size. With increasing temperature, ε′ enhances and the ε″ peak shifts to higher frequency, indicating a thermally activated relaxation process. The activation energy for relaxation is nearly comparable to that for grain conduction, implying the polarization process depends on the conducting of the charge in the grain interior. Complex impedance spectroscopy analysis shows the dielectric behavior is attributed to the boundary-layer capacitor mechanism and existing huge polarization.     

Giant dielectric permittivity of Ca and Sb-co-doped TiO2 ceramics

The continuous development of microelectronic devices with integrated functions has led to an increasing interest in the development of dielectric ceramics with high dielectric constant, low dielectric loss, good frequency, and temperature stability. In this work, (Ca, Sb)-co-doped TiO₂ (CSTO) ceramics were prepared by solid-phase reaction sintering method and their phase structure, microstructure, giant dielectric properties, and mechanism were systematically investigated. The results show that the secondary phase of CSTO ceramic samples appeared when x?≥?4%. The average grain size of CSTO ceramics decreased as the amount of doping increases, and all CSTO ceramics had giant dielectric constants. When the doping amount was x?=?4%, the CSTO ceramics obtained optimum dielectric properties, where ε′ = 2.6?×?10⁵ and tan δ?=?0.10. X-ray photoelectron spectroscopy (XPS) results showed that the giant dielectric origin was mainly due to the Sb⁵⁺ doping that generated electrons inside the material, Ca²⁺ doping that enhanced the generation of vacancies inside the material, and the defective dipole clusters produced that improved the dielectric properties of the CSTO ceramics. This work is critical for the development and deployment of new TiO₂-based giant dielectric ceramics.

     

Effects of Li and Fe doping on dielectric relaxation behavior in (Li,Fe)-doped NiO ceramics

High permittivity (Li, Fe)-doped NiO (LFNO) ceramics are prepared by a simple PVA sol–gel route and their dielectric properties are investigated as functions of temperature and frequency. It is found that the concentrations of Li and Fe have strong influences on the microstructure and dielectric properties of the LFNO ceramics. Two thermally activated dielectric relaxations are observed in the Li_0.05Fe_0.10Ni_0.85O ceramic sample with the activation energies of 0.448 and 0.574 eV for the high- and low-frequency relaxations, respectively. By using a complex impedance analysis, it is believed that the high-frequency relaxation is closely related to the transport properties inside the grains, and the low-frequency relaxation might be ascribed to the interfacial polarization at the interface layers of grain boundaries and/or NiFe₂O₄ secondary phase layers.     

微波介质陶瓷的介电损耗研究进展

综述了微波介质陶瓷介电损耗理论与实验研究的最新进展,讨论了陶瓷体系中气孔、第二相、杂质等微结构对介电损耗的影响,介绍了远红外光谱-阻尼谐振子模型在介电损耗研究中的应用以及双声子过程或多声子过程对介电损耗的贡献,并对微波介质陶瓷研究的发展做了展望.     

高介电陶瓷材料在油品介电精制方法中的应用

目前对于介电材料的研究与应用一般集中于电子产品及其相关领域，高介电陶瓷材料应用于油品精制领域还是一个新的尝试。首先简要介绍了介电力学精制工艺装置，并重点讨论了介电陶瓷在其中的应用及基本原理，最后选用几种不同介电常数的介电陶瓷材料在装置中进行了实验，实验证明，高介电陶瓷材料对油品有较好的精制效果，并且对于所选用的几种介电材料而言随着介电常数的增加精制效果也提高。     

新型微波介质陶瓷材料与元件的研制

报告本课题组承担的863计划项目“新型微波介质陶瓷材料与元件的研制”，在实验工作中不仅采用传统的固相反应法而且利用共沉淀和水热合成等溶液反应技术，还采用凝胶浇注成型复杂形状的微波陶瓷元件，并利用流延成型技术制备大尺寸微波集成陶瓷基板等；研制成功具有高电容率和品质因子并接近于零的谐振频率温度系数的系列化微波介质陶瓷；开发成功多种微波介质元器件，包括：介质谐振器、介质滤波器、GPS片式天线、微波电容器、通信电缆滤波接头和微波集成基板等。     

高介电常数微波介质陶瓷的研制及其同轴型滤波器的仿真

本文研制了一种由双镧系元素组成的BaO-Ln2O3-TiO2(BLT)系高介电常数、低损耗材料,并以该材料为基础,设计并研究了其独石型同轴滤波器。滤波器采用新颖的凹槽式电感耦合和一端金属面短路的λ/4结构。利用HFSS高频仿真软件对该滤波器的传输特性进行了仿真,表明其具有中心频率为1.83GHz、带宽43MHz、插入损耗小于0.5dB、带内纹波为1.5dB的优异的通带特     

Structural and dielectric properties of complex PLZT ceramics

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Mechanical and dielectric failure of BaTiO3 ceramics

Both at room temperature and above the Curie temperature, Weibull plots for the mechanical and dielectric strengths of BaTiO₃ thick films sintered 1300° C to 1400° C showed good a correlation. The present results indicate that the microstructure plays a similar role in both mechanical and dielectric failures and firmly suggest that the fracture origins in both failures are analogous, possibly surface flaws associated with grain size. Specimens sintered at 1450° C showed a bend in the Weibull distribution for mechanical strength. This bimodal Weibull distribution was explained by the assumption that the geometric relation between the ratio of grain sizes to specimen thickness and stress gradient under a three-point bending condition affects the effective tensile stress of the tips of surface flaws.     

Structural and dielectric properties of La-doped lead titanate ceramics

(Pb_1−xLa_x)TiO₃ (PLT) ceramics of perovskite type were prepared by sol-gel process, and their structural and dielectric properties investigated. The obtained compounds crystallize, under heat treatment, at relatively low temperatures and no secondary phases have been observed on the corresponding XRD spectra. Annealing temperature (T_a) and its duration (t_a) appear to influence notably their structural and dielectric characteristics.     

PMN-xPT陶瓷的介电温谱拟合与分析

用双机制模型分析、拟合了不同PT组份弛豫型铁电陶瓷PMN-xPT的介电行为.研究表明随着PT组份的增加,极化机制发生明显的变化.通过分析极化机制随频率变化的情况,解释了Tm与ω的V-F关系的拟合参数随频率区间改变的现象.     

ZnO掺杂对CLST微波介质陶瓷烧结及介电性能的影响

研究了烧结助剂ZnO对CaO-Li2O-Sm2O3-TiO2(简写为CLST)系微波介质陶瓷的烧结特性及介电性能的影响.结果表明:ZnO的添加能有效地降低CLST陶瓷的烧结温度至1150℃.掺杂2wt%ZnO的CLST陶瓷取得了较好的介电性能:εr=84,tanδ=0.009,τf=-15ppm/℃.     

Dynamic response of electrical,dielectric and magnetic properties of La-substituted Ni-Cu-Cd bulk ceramics with structural rietveld refinement

Journal of Materials Science: Materials in Electronics - Bulk dense ceramics are needed in many electronic applications instead of powder with grain in the nanometric range that is the prime...     

Improvement of thermoelectric properties of WO3 ceramics by NiO addition

The thermoelectric properties of tungsten trioxide (WO₃) ceramics doped with nickel oxide (NiO) were investigated from 323 up to 1,023 K. The results revealed that doping WO₃ with NiO could promote the grain growth and the density. There was a second phase (NiWO₄) segregation at the grain boundaries in the samples containing more than 1.0 mol% NiO, which inhibited the further grain growth. The magnitude of the electrical conductivity (σ) and the absolute value of the Seebeck coefficient (|S|) depended strongly on the NiO content. As for the power factor (σS ² ), the 1.0 mol% sample has the maximum value of the power factor which is 0.55 μW m^?1 K^?2 at 1,023 K.     

Li和Ti共掺NiO薄膜的溶胶-凝胶法制备及其介电性能

采用溶胶-凝胶法在Pt/Ti/SiO2(1mm)/Si基板上制备了Li和Ti共掺NiO基新型无铅介电薄膜材料,研究了薄膜的形貌、结构、介电性能.结果表明,热分解温度(300～500℃)对薄膜结构影响不明显,经600～800℃退火后的薄膜由NiO与Li-Ni-O复合氧化伆组成;经300℃热分解处理、650℃退火后的薄膜,其表面均匀致密,膜厚约300nm,室温下100Hz时的介电常数为767,当频率高于3000Hz后,介电常数随频率的增加趋于减小.