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Microwave Properties (microwave + property)
Selected AbstractsFabrication of Ceramic,Polymer Photonic Crystals by Stereolithography and Their Microwave PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002Soshu Kirihara Three-dimensional photonic crystals with periodic variations in the dielectric constant were fabricated using a stereolithographic rapid prototyping method. The structures were composed of millimeter-scale ordered epoxy lattices in which ceramic particles with high dielectric constants (such as silica and titania) were dispersed. These crystals were designed to reflect microwaves via the formation of photonic band gaps in a gigahertz range. The attenuation of transmission amplitude through the photonic crystals, which was measured as a function of frequency using a network analyzer, clearly showed the formation of band gaps in the microwave range. [source] Effect of Nb2O5/ZnO Addition on Microwave Properties of (Zr0.8Sn0.2)TiO4 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2001Yong Hwan Park The effects of Nb2O5 and ZnO addition on the dielectric properties, especially the quality factor, of (Zr0.8Sn0.2)TiO4 (ZST) ceramics were investigated in terms of the sintered density acquired by the zinc. For ZST ceramics with 2 mol% added ZnO, the relative density of the samples decreased with >0.5 mol% addition of Nb2O5. On the other hand, for samples with 6 mol% added ZnO, the relative density remained >97%, even when the amount of Nb2O5 was increased to 2.0 mol%. When >0.5 mol% Nb2O5 was added, both the quality factor and the dielectric constant exhibited similar trends with sintered density. The ZST ceramics with 6 mol% added ZnO, especially, still manifested a quality factor >40 000 and a dielectric constant of 37, even when the amount of Nb2O5 was increased, values that are not explainable by the previously suggested electronic defect model. [source] Preparation, Characterization, and Microwave Properties of RETiNbO6 (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, and Yb) Dielectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2001Mailadil T. Sebastian Microwave ceramic dielectric resonators (DRs) based on RETiNbO6 (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, and Yb) have been prepared using the conventional solid-state ceramic route. The DR samples are characterized using XRD and SEM methods. The microwave dielectric properties are measured using resonant methods and a net work analyzer. The ceramics based on Ce, Pr, Nd, and Sm have dielectric constants in the range 32,54 and positive coefficient of thermal variation of resonant frequency (,f). The ceramics based on Gd, Tb, Dy, Y, and Yb have dielectric constants in the range 19,22 and negative ,f. [source] Textured Microstructure and Dielectric Properties Relationship of BaNd2Ti5O14 Thick Films Prepared by Electrophoretic DepositionADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Zhi Fu Abstract An alternative approach to tailor the temperature coefficient of permittivity (TC,r) of high Q dielectric BaO,Re2O3,TiO2 (Re: rare earth elements) thick films is presented. 10- to 80-µm-thick BaNd2Ti5O14 (BNT) films are fabricated by electrophoretic deposition on Pt foils under different processing conditions. Observed anisotropic grain growth is facilitated by constrained sintering. The increase of the sintering temperature increases markedly the aspect ratio of the grains, decreases the dielectric permittivity and TC,r changes from ,114 to +12,ppm °C,1. By controlling the sintering temperature, near-zero TC,r, high Q thick films can be fabricated with 45,<,,r,<,70. These findings are of technological relevance since they demonstrate that control of substrate constraint and sintering conditions can be used to control grain anisotropy and thus microwave properties of the BaO,Re2O3,TiO2. The thick films facilitate scaling to small device sizes for high frequency operation. Similar observations are expected in other microwave systems thus opening further technological opportunities. [source] Microwave Dielectric Ceramics for Resonators and Filters in Mobile Phone NetworksJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2006Ian M. Reaney Temperature-stable, medium-permittivity dielectric ceramics have been used as resonators in filters for microwave (MW) communications for several decades. The growth of the mobile phone market in the 1990s led to extensive research and development in this area. The main driving forces were the greater utilization of available bandwidth, that necessitates extremely low dielectric loss (high-quality factor), an increase in permittivity so that smaller components could be fabricated, and, as ever in the commercial world, cost reduction. Over the last decade, a clear picture has emerged of the principal factors, that influence MW properties. This article reviews these basic principles and gives examples of where they have been used to control microwave properties and ultimately develop new materials. [source] Low-Fire Processing (Ca1,xNd2x/3)TiO3 Microwave CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003Chih-Hung Wei Effects of 3ZnO·2B2O3 (3Z2B) glass addition on densification and microwave properties of (Ca1,xNd2x/3)TiO3(CNT-X) have been investigated. With the 3Z2B glass content greater than 20 vol%, the densification temperature can be greatly reduced from 1400°C for pure CNT-X to 850°,900°C for CNT-X + 3Z2B microwave ceramics. The above result is attributed to a chemical reaction taking place at the interface of 3Z2B/CNT-X during firing. The Ca in CNT-X dissolves into 3Z2B, forming a new glass of CaO-ZnO-B2O3 at 870°,880°C which enhances the densification kinetics of 3Z2B + CNT-X microwave ceramics. For the samples with 20,40 vol% 3Z2B, the resulting 3Z2B + CNT-X microwave ceramics have a dielectric constant (k) of 30,60 and a quality factor (Q) of 200,550 at 1,10 GHz, and a temperature coefficient of resonant frequency of 20,60 ppm/K in the temperature range of 20°,80°C. [source] Preparing Low-Loss Low-Temperature Cofired Ceramic Material without Glass AdditionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Heli Jantunen A low-temperature cofired ceramic (LTCC) composition for radio-frequency purposes was accomplished without prior glass preparation. In this process, the formulation was made by mixing the glass-forming oxides (ZnO, SiO2, and B2O3) with the commercial microwave ceramic MgTiO3,CaTiO3. The sintering, microstructure, and microwave properties were compared to a formulation with exactly the same composition, but a conventional production route, including glass preparation. The novel preparation route resulted in improved firing properties of the mixture. Also, the densities, porosities, and phases of the samples were almost the same as those of the conventional samples, but the phase fractions were different. Finally, this preparation route produced better dielectric values. [source] Microwave measurement uncertainty due to applied magnetic fieldPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007S. Perero Abstract In recent years there has been a wide interest in the production and analysis of films and nanostructures of different types for their microwave properties up to the mm-wave range. In order to characterize the electromagnetic behavior of these devices new experimental techniques need to be developed and assessed. Typically the measurements involve the use of vector network analyzer, and require several calibration steps. In this paper, we present a summary of the calibration techniques and evaluate the uncertainties obtained under different conditions, with a particular focus on the effect of the applied magnetic field upon uncertainty. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] New antistatic charge and electromagnetic shielding effectiveness from conductive epoxy resin/plasticized carbon black compositesPOLYMER COMPOSITES, Issue 2 2008Nadia Abdel Aal Recently, there is an increasing interest in electromagnetic interference shielding due to the rapid increase in electromagnetic pollution and the wide use of commercial and military products. Conducting polymer composites were prepared in the presence of epoxy resin and plasticized carbon black (CB). The structural characteristics of the composites were examined by means of scanning electron microscopy, cross linking density, and interparticle distance among conductive particles. The mechanical properties such as Young's modulus, elongation at break, and hardness of the composites were investigated as a function of CB content. The results indicated that CB could improve the composite microstructure. The higher mechanical behavior than green epoxy can be attributed to the interaction between CB particles and epoxy resin. The conductivity, mobility carriers, and number of charges of the composites at room temperature were found to be dependent on CB content. The applicability of the composites to antistatic charge dissipation was examined. Dependence of the microwave properties of the epoxy/CB composites on the volume fraction of CB particles and frequency were studied. Moreover the permittivity as a function of frequency of the composites was studied. The electromagnetic wave shielding of epoxy/CB composites is dominant by both reflection and absorption. Composites can find applications in antistatic charge dissipation and in suppression of electromagnetic interference and stealth technology. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers [source] | ||||||||||