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11.
《应用陶瓷进展》2013,112(4):225-233
Abstract Abstract Lead free perovskite Ba(La1/2Nb1/2)O3 was prepared by conventional ceramic fabrication technique at 1375°C for 7?h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single phase monoclinic structure with space group P2/m. Energy dispersive X-ray analysis and scanning electron microscopy studies were carried to study the quality and purity of the compound. Permittivity data showed low temperature coefficient of capacitance (T CC = 11%) up to 100°C. The circuit model fittings were carried out using the impedance data to find the correlation between the response of real system and idealised model electrical circuit. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(La1/2Nb1/2)O3. The AC conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy. 相似文献
12.
L. Young 《Electrochimica acta》2008,53(22):6542-6544
The decrease with time in the capacitance of anodic oxide films on tantalum after ceasing film growth by reducing the field in the oxide was investigated. No dependence was observed of the amount and rate of change in relative dielectric permittivity on the initial current density. The kinetics of this effect are therefore different from those for the decay of the latent ionic conductivity. 相似文献
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本文根据Barlow提出的在TE(01n)模谐振腔上耦合一段截止波导构成复合腔的原理,首次在C波段对介质谐振器材料的介电性能进行了测量,并从理论上证明了该方法对相对介电系数有很高的测试灵敏度,本文给出了几种介质谐振器材料的测试结果,最后就样品厚度对测试精度的影响作了分析。 相似文献
14.
《Ceramics International》2023,49(13):21402-21410
Dielectric ceramics with high permittivity and low loss are widely used in electronic components and devices. In this study, (Nb, Zn) co-doped NbxZnySn1-x-yO2 with different doping levels and Nb/Zn ratios was designed to tune the defect structure toward the optimal dielectric performance. The lattice parameters firstly increased from x = y = 0.01 to 0.03 and then decreased, while the oxygen vacancy concentration decreased with doping. The co-doped sample with x = y = 0.02 exhibits stable permittivity up to 800 with an ultra-low loss tanδ ∼0.03 at 40 Hz. DFT calculation showed that the oxygen vacancy was formed with single-Zn doping and co-doping at low doping level, while the hole was generated at higher doping level. The achieved large permittivity and low loss of the sample are related to both Electron-Pinned Defect Dipoles (EPDD) and Hole-Pinned Defect Dipoles (HPDD) effects in the lattice, which was determined by the relative positions of donor and acceptor dopants. 相似文献
15.
《Ceramics International》2023,49(16):26675-26682
Phase formation, microstructure, magnetic properties, and dielectric properties of Ba1.5Sr1.5Co2Fe(23−x)CrxO41 (0.0 ≤ x ≤ 1.0) ceramics, in which Fe3+ ions were substituted by Cr3+ ions, were systematically investigated. X-ray diffraction results reveal that Z-type hexagonal ferrite was formed by sintering at 1250 °C, and Cr3+ ions successfully enter lattice without destroying crystal structure. Analysis of the microstructure reveals that Cr3+ ion doping has significant effect on crystal micromorphology. Samples with x = 0.4 have the most homogeneous micromorphology and the highest sintering density of 5.12 g/cm3. In addition, under the influence of external magnetic field, all samples exhibit typical soft magnetic character and hysteresis characteristics, with saturation magnetization up to 63.86 emu/g (x = 0.6). Particularly, compared with undoped sample, Cr-doped samples have outstanding magnetic–dielectric properties. Firstly, with increasing Cr3+ amount, real part of the permeability (μ′) reaches the maximum value of 10.70 at x = 0.4, while cutoff frequency exceeds 2 GHz, and Snoek constant reaches ∼19.50 GHz. Furthermore, due to more homogeneous microstructure, samples with x = 0.4 have low magnetic loss and can maintain high quality factor (Q) over a broad frequency range. Moreover, real part of the permittivity (ε′) reaches the maximum value of 16.90 at x = 0.6, and dielectric loss remains lower than 0.013 for frequencies below 0.7 GHz. Consequently, magnetic–dielectric materials prepared in this work are expected to have extensive application prospects for ultrahigh-frequency devices. 相似文献
16.
Sub-surface radar is becoming increasingly popular as an inspection method. Interpretation can be enhanced if uncertainties about the dielectric properties of the concretes under investigation are removed. The need for reliable data to identify possible variations of the dielectric properties of different concrete mixes and their condition on site has led to a systematic laboratory based experimental programme under the auspices of a major European Commission (Brite-Euram III Framework 4) funded project. Some key results from this recently completed work are presented in this paper with practical implications related to field surveys of structural concrete. 相似文献
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A new method based on amplitude-only reflection measurements for complex permittivity determination of low-loss materials backed by a short-circuit termination is presented. There are two main advantages of the proposed method. First, it is insensitive to calibration plane shifts and phase uncertainties in reflection measurements of low-loss materials. Second, it does not require any additional test material with a thickness value different than that of the material under test. The disadvantage of the proposed method is that it is not convenient to apply for complex permittivity determination of dispersive low-loss materials. The method is validated by complex and amplitude-only scattering parameter measurements at X-band of a low-loss sample (polystyrene) fitted into a waveguide section. The method, as other non-resonant methods, can only provide a rough indication of the imaginary part of the permittivity for low-loss samples. 相似文献