Papers by Keyword: Microwave Properties

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Authors: F.M.M. Pereira, A.S.B. Sombra
Abstract: The Ferrite term is used to refer to all magnetic oxides containing iron as major metallic component which has great to technological applications because of their ferromagnetic and insulating properties at room temperature. Among such ferrites, the hexagonal ones (hexaferrites) have long been used for permanent magnets and are of interest for microwave applications. The hexaferrite M-type has a structure built up from the S blocks interposed by the R block and are symbolically described as RSR*S*. In the last decades there has been great interest in the hexaferrites M-Type for applications as electronic components for mobile and wireless communications at microwave/GHz frequencies, electromagnetic wave absorbers for electromagnetic compatibility (EMC), radar absorting material (RAM) and stealth technologies and as composite materials. This review aimed study the structure, magnetic and dielectric properties of the hexaferrite BaxSr1-xFe12O19, which is a promising material for electronic devices and for small dielectric resonator antennas (MRA).The outline of this Review Paper is as follows:
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Authors: Yong Jiang Di, Deng Ming Chen, Peng Jun Cao, Bi Jia
Abstract: The microwave properties of Glass-coated FeCuNbVSiB and CoFeNiSiB microwires/dielectric composite with different microwires diameters were studied. Relative complex permeability and complex permittivity was measured by transmission/reflection (T/R) coaxial line method at the frequency range of 2-18 GHz for composite samples. The results show that the microwave permeability and permittivity increases with the lengthening of the microwires in composite. The microwave permeability, natural resonance frequency and microwave permittivity increase with the decrease of the diameter of the microwires.
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Authors: Hai Tao Wu, Yi Shan Jiang, Ying Zi Wang, Ya Ming Chen, Yun Long Yue
Abstract: Corundum-type magnesium niobate (Mg4Nb2O9) ceramics were synthesized by the conventional solid-state method, the effect of ball milling time on microwave properties was studied in detail. Xrd results showed that the major phase was identified as the ordered corundum structure Mg4Nb2O9 with minor secondary phase of orthorhombic-symmetry Mg5Nb4O15. The morphology was obviously affected by ball milling times at sintering process, and then the relationships between the morphology and microwave properties were discussed. The results indicated that ball milling times at sintering process could obviously affect the microstructure and microwave properties of Mg4Nb2O9 ceramics. When ball milling time was 10h, the Mg4Nb2O9 ceramics were prepared with the conditions of calcination at 1100°C for 2h and sintered at 1350°C for 6h, and the optimal microwave properties were εr~13, Q·ƒ~120,000GHz and ƒ~-60ppm/°C.
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Authors: Hai Tao Wu, Yi Shan Jiang, Ying Zi Wang, Ya Ming Chen, Yun Long Yue
Abstract: Corundum-type magnesium niobate (Mg4Nb2O9) ceramics were synthesized by the conventional solid-state method, the effect of holding time during calcination and sintering process on microwave properties was studied in detail. The xrd results showed that the major phases were identified as the ordered corundum structure Mg4Nb2O9 with minor secondary phases of orthorhombic-symmetry Mg5Nb4O15. The morphology was obviously affected by holding times at sintering process and the relationships between the morphology and microwave properties were discussed. The results indicated that holding time at calcination process had negligible effect on the microstructure and microwave properties, while holding time at sintering process could obviously affect the microstructure and microwave properties of Mg4Nb2O9. When calcination at 1100°C for 2h and sintered at 1350°Cfor 6h, the optimal microwave properties were εr~13, Q·ƒ~130,000GHz and τf~-50 ppm/°C.
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Authors: Yi Shan Jiang, Ying Zi Wang, Ya Ming Chen, Yun Long Yue, Hai Tao Wu
Abstract: Microwave dielectric ceramics of Mg4Nb2O9 were prepared by the solid-state method and their microwave dielectric properties and microstructure were investigated in this study. The sintering ability and microwave dielectric properties of Mg4Nb2O9 ceramics were studied under various sintering temperatures ranging from 1200°C to 1350°C. As the sintering temperature increased from 1200°C to 1350°C, the density values, the εr values and the Q·ƒ values increased and saturated at 1350°C.The ƒ values were ranged from -48.7 to -57.8 ppm/°C. Due to the increased density and appropriate grain growth the Mg4Nb2O9 ceramics sintered at 1350°C had the excellent microwave dielectric properties of εr=12.3, Q·ƒ =108,000GHz and ƒ=-55.3ppm/°C.
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Authors: Kai Xin Song, Peng Zheng, Xiao Ping Hu, Jiang Xiang Deng, Jun Wu, Jun Ming Xu, Zhi Hua Ying, Liang Zheng, Hui Bin Qin
Abstract: In this paper, the dependance of microstructures on temperature stability of the (Mg1-xCax)2SiO4 (0≤x≤0.5) ceramics prepared by the conventional solid-state route were investigated. The XRD and SEM testing results showed the (Mg1-xCax)2SiO4 ceramics were mainly composed of both forsterite (Mg2SiO4) phase and Monticouite (MgCaSiO4) phase. Significantly, with increasing x, the ceramic temperature coefficients of resonant frequency (τf) were strongly correlated to the ceramic crystalline phase compositions and could be adjusted to near zero value through changing the contents of both phases. And its dielectric constants (er) were kept in the range of 6.8 to 8.7, and the quality factors (Q×f value) in the range of 18, 080 GHz to 55, 840 GHz at 15GHz.
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Authors: Sea Fue Wang, Yuh Ruey Wang, Thomas C.K. Yang
Abstract: In this study, the feasibility for use of multiphase BaTiO3 ceramics as microwave dielectric resonators was evaluated through the substitution of metal ions in B sites, such as ions of Mn, Co, Mg, In, Fe, Zn, and Ni. The effects of metal ions substitution and sintering conditions on the densification, microstructural evolution and microwave properties of the BaTiO3 ceramics containing cubic and hexagonal phase were examined.
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Authors: Janina Mazierska, Kenneth Leong, Dimitri Ledenyov, Adam Rains, Nina Zuchowski, Jerzy Krupka
Abstract: Typically microwave properties of High Temperature Superconducting films are defined in terms of surface resistance Rs computed from Q-factor measurements obtained using one of resonant techniques. While NdBaCuO films are known to have higher TC and JC than YBaCuO films, not much is known about their loss at high frequencies. In this paper we report on microwave properties of NdBaCuO films of varying quality and thickness based on measurements with a 25GHz sapphire Hakki Coleman resonator and computations using two approaches: the surface resistance and the complex conductivity as primary variables for rigorous electromagnetic solutions.
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Authors: Viktor Vekky Ronald Repi, Azwar Manaf, Bambang Soegiono
Abstract: Mn-Ti substituted Barium - Strontium Hexaferrite and Barium – Lanthanum Manganite both well established materials which have been shown poses microwave absorbtion properties. As the properties of composite system are a composition sensitive, composite materials must be properly designed to meet a specific application. In this paper, we report our recent investigation on microwave absorbtion properties of composite Ba0.5Sr0.5Fe11.7Mn0.15Ti0.15O19/La0.7Ba0.3MnO3 system. Composite components respectively Ba0.5Sr0.5Fe11.7Mn0.15Ti0.15O19 and La0.7Ba0.3MnO3 were prepared through mechanical alloying route employing a planetary ball mill for 20 hrs. The two milled powders were sintered at a temperature 1100 °C for 10 hours to ensure the crystallization towards fully crystalline materials. Composites with 2 different compositions were studied by FTIR and VNA from which results were compared with that of each component. Results of the investigation concluded that, the composite of Ba0.5Sr0.5Fe11.7Mn0.15Ti0.15O19/La0.7Ba0.3MnO3 system is a good microwave absorbing material in the frequency range 9 GHz-15 GHz, particularly, sample with coded A03B07 has a wide range frequencies absorption.
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