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Comparative study on structure and properties of ZnO thin films prepared by RF magnetron sputtering using pure metallic Zn target and ZnO ceramic target
摘要： In this work, ZnO thin films was deposited onto Si substrate by ablation of different sputtering targets (ZnO ceramic target and pure metallic Zn target) under different substrate temperatures from 300°C to 600°C with intervals of 100°C, and the properties of ZnO thin films were analysed. The results showed that ZnO thin films had the c-axis preferred orientation and it also presented optimised properties owing to the reduction of thin film defects at a substrate temperature of 400°C. By analysing data, it could also be seen that the performance of ZnO thin films fabricated using the ZnO ceramic target was better than that of ZnO thin films fabricated using the pure metallic Zn target. It was considered that the excellent properties of ZnO thin films fabricated using the ZnO ceramic target were attributed to the decrease in oxygen vacancies and the reduction of film defects.
关键词： ZnO ceramic target,RF magnetron sputtering,pure metallic Zn target,ZnO,thin films
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Auckland, New Zealand (2018.8.5-2018.8.8)] 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Influence Analysis of ZrO<inf>2</inf> Ceramic for Cellular Phones on 5G mm-Wave Antenna Performance
摘要： In this paper, the influences of ZrO2 ceramic on the fifth generation mobile communications (5G) millimeter-wave (mm-Wave) antenna performance are studied. A 28-GHz 2 × 2 non-stacked patch antenna array and a 28-GHz 2 × 2 stacked patch antenna array are designed on dielectric substrates as the performance baseline. Based on the two types of antenna arrays, various ZrO2 ceramic thicknesses and various gaps between the ZrO2 ceramic and the antenna arrays are simulated to get quick understanding of the ZrO2 ceramic influence on the antenna performance. From the simulated results, it can be found that the ZrO2 ceramic has different influences on different types of antenna arrays. Besides, for both of the two types of antenna arrays, when the thicknesses of ZrO2 ceramic are close or equal to integer multiples of 0.5 guided wavelengths ((cid:540)g), the antenna performance in the material-loading cases gets close to that in the free space (FS). Also, when the thicknesses of ZrO2 ceramic are close or equal to odd multiples of 0.25 (cid:540)g and the gaps between the ZrO2 ceramic and the antenna array are close or equal to integer multiples 0.5 FS wavelengths ((cid:540)0), the focusing effects of electromagnetic (EM) beams get significant for both arrays. The findings comply with the EM wave propagation theory and can be applied to radome designs of Terahertz (THz) antenna arrays.
关键词： 5G,mm-Wave,ZrO2,THz,ceramic,antenna
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Preparation and Characterization of Epoxy and Hollow Ceramic Spheres Composites
摘要： High crash strength and high thermal conductivity hollow ceramic sphere with external diameters between 250 and 420 micrometers were produced by firing green bodies prepared in a fluidized reactor at room temperature. Then these spheres were bonded together by epoxy resin to produce composites with very high filler concentration but light weight. The dielectric, thermal and mechanical properties of the composites were investigated. Because the component in the raw materials of hollow ceramic spheres is varied, the corresponding composites have tunable permittivity and dielectric loss. In the composites, hollow ceramic spheres are nearly close packed, which can be observed by optical microscope. The novel close packed structure of these spheres endows the composites with highly efficient pathways for heat dissipation and reliable framework of bearing compressive loading. The surfaces of the spheres were modified by 1wt. % silane coupling agent, KH-560, before combining with epoxy resin in order to improve their chemical compatibility with epoxy resin. With TGA results, we can see that the epoxy resin in the composites has a low percentage of mass ratios and thus plays a role as binder to combine neighboring hollow ceramic spheres together. The results demonstrate improvement of dielectric and thermal conducting properties of epoxy resin, and feasibility of extending its working ranges in both compression strength and temperature as a multifunctional material in insulating area.
关键词： Compressive strength,Thermal conductivity,Composites,Ceramic spheres
更新于2025-09-09 09:28:46
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[IEEE 2018 48th European Microwave Conference (EuMC) - Madrid, Spain (2018.9.23-2018.9.27)] 2018 48th European Microwave Conference (EuMC) - Liquid Crystal Based SPDT with Adjustable Power Splitting Ratio in LTCC Technology
摘要： This paper presents design and characterisation of a new liquid crystal (LC) based single-pole double-throw (SPDT) with continuously adjustable power splitting ratio in low temperature co-fired ceramic (LTCC) technology. It is designed for a centre frequency of 30 GHz, the fully embedded LC phase including a key component, shifter in stripline topology. The SPDT shows a good matching with |S11| = ?10 dB over a bandwidth of 18 %. It exhibits an insertion loss of 9 dB to 11 dB and an isolation between 22 dB to 32 dB. The continuous tuneability not only allows the selection of each preferred power splitting ratio at the output ports, but also a tuning of the centre frequency. The high insertion loss arises from a certain surface roughness as well as a decreased conductivity of the gold metallisation used.
关键词： single-pole double-throw (SPDT),low temperature co-fired ceramic (LTCC),Liquid crystal
更新于2025-09-04 15:30:14
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A new design of the YIG/MTC joint brazed by bismuth-based glass
摘要： The paper uncovers an underlined mechanism of joining Yttrium Iron Garnet (YIG) and Magnesium Titanate Ceramic (MTC) with a bismuth-based glass braze. The proposed joint design has not been investigated until present. The central hypothesis is as follows. The brazed bismuth-based glass microstructure and the resulting mechanical strength of a YIG/MTC joint design support favorably a good bonding of the interface domains. The supporting evidence includes the following: (i) the bismuth-based glass features good wettability on YIG and MTC, (ii) the sequence of the coefficients of thermal expansions (YIG, bismuth-based glass, MTC) is in a favorable succession. The study reveals that the interface reactions form: (i) a lamellar phase and YBO3 whiskers at the YIG/Bi25 interface, (ii) both MgFe2O4, and Bi4Ti3O12 whiskers in addition to Zn2Ti3O8 reaction layer at the MTC/Bi25 interface, and (iii) Fe2O3 phase along the brazing seam. The mechanical integrity of joints has been studied as well.
关键词： Magnesium titanate ceramic,Whiskers,Microstructure,Bismuth-based glass braze,Yttrium iron garnet ferrite
更新于2025-09-04 15:30:14
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Effect of Ti addition on the wetting and brazing of Sn0.3Ag0.7Cu filler on SiC ceramic
摘要： The wetting behavior of Sn0.3Ag0.7Cu (SAC) filler with the addition of Ti on SiC ceramic was investigated using sessile drop method. SiC/SiC was brazed by SAC-Ti filler with different Ti content at 1223 K (950 °C) for 10 minutes. The wettability of SAC-Ti filler on SiC was significantly enhanced with the addition of Ti. The contact angle decreased at first and then increased with increasing Ti content. The lowest contact angle of 9° was obtained with SAC-1.5Ti (wt.%) filler. When Ti content further increased to 2.0 wt.%, the contact angle increased, due to the intense reaction of Ti-Sn. The reaction between Ti and SiC controlled the wetting behavior of SAC-Ti on the SiC substrate and the reaction products such as TiC and Ti5Si3 were formed. The wetting of SAC-Ti on SiC was reaction-controlled. Interfacial reaction products TiC and Ti5Si3 were observed. The wetting activation energy in spreading stage was calculated to be 129.3 kJ/mol. Completely filled SiC/SiC joints were obtained using the filler with Ti content higher than 0.5 wt.%. The fillet height increased firstly then decreased with mounting Ti content. The shear strength of joints increased first with the addition of Ti then decreased with Ti content increasing to 2.0 wt.%. The highest shear strength of 35.7 MPa was obtained with SAC-1.5 Ti (wt.%) filler.
关键词： wetting,brazing,Ti addition,Sn0.3Ag0.7Cu,SiC ceramic
更新于2025-09-04 15:30:14
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Fabrication and electrical characterization of (Bi0.49Na0.49Ba0.02)TiO3-PVDF thin film composites
摘要： The barium doped bismuth sodium titanate (i.e., Bi0.49Na0.490.98Ba0.02)TiO3 (BNBT) powder was prepared by a conventional ceramic processing route. The thin film composites of BNBT- PVDF (polyvinylidene fluoride) were fabricated via a solution casting route. The scanning electron micrographs of the thin film samples show the homogenous distribution of grains with absence of cracks/pores. It is observed that with the increase of BNBT content in PVDF leads to enhancement in the dielectric permittivity and the reduction in the dissipation factor (tangent loss). The various electrical properties of the thin film samples were studied in the frequency range of 1 kHz to 1 MHz at different temperature between 25 and 100 °C. The prepared composite films have been used to study the (a) relationship between properties and crystal structure and (b) relaxation and conduction mechanism through the complex modulus and impedance spectroscopy. The contribution of grains was analyzed in the composite films by the fitting of equivalent circuit with the experimental data. An existence of the non-Debye type of dielectric relaxation was indicated by studying of the impedance and modulus parameters. The calculated activation energy from the temperature dependence of AC conductivity depicts hopping nature of charge carriers, which further explain the conduction process and mechanism in the prepared composites.
关键词： Impedance spectroscopy,Dielectric,Ceramic-polymer composites
更新于2025-09-04 15:30:14
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Additive-Manufacturing of 3D Glass-Ceramics down to Nanoscale Resolution
摘要： Fabrication of a true-3D inorganic ceramic with resolution down to nanoscale (～ 100 nm) using sol-gel resist precursor is demonstrated. The method has an unrestricted free-form capability, control of the ?ll-factor, and high fabrication throughput. A systematic study of the proposed approach based on ultrafast laser 3D lithography of organic-inorganic hybrid sol-gel resin followed by a heat treatment enabled formation of inorganic amorphous and crystalline composites guided by the composition of the initial resin. The achieved resolution of 100 nm was obtained for 3D patterns of complex free-form architectures. Fabrication throughput of 50 × 103 voxels/s is achieved; voxel - a single volume element recorded by a single pulse exposure. A post-exposure thermal treatment was used to form a ceramic phase which composition and structure were dependent on the temperature and duration of the heat treatment as revealed by Raman micro-spectroscopy. The X-ray diffraction (XRD) showed a gradual emergence of the crystalline phases at higher temperatures with a signature of cristobalite SiO2, a high-temperature polymorph. Also, a tetragonal ZrO2 phase known for its high fracture strength was observed. This 3D nano-sintering technique is scalable from nanoscale to millimeter dimensions and opens a conceptually novel route for optical 3D nano-printing of various crystalline inorganic materials de?ned by an initial composition for diverse applications for microdevices designed to function in harsh physical and chemical environments and at high temperatures.
关键词： ultrafast 3D laser nanolithography,3D nanoscale optical printing,inorganic 3D structures,high-temperature glass-ceramic materials,calcination
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - A 120 GHz LTCC Packaged Horn Antenna with a Radome and Soft Surface Structure
摘要： A 120 GHz step-profiled horn antenna integrated in low-temperature co-fired ceramic (LTCC) packages with a radome is presented in this paper. As an antenna-in-package (AiP) design, the proposed hollow horn structure is constructed by the cavities with several surrounding fences of vertical metallic vias in multilayer LTCC substrates. In consideration of the practical application, co-design with a thick cylindrical radome attached to the surface of the antenna is also studied. A planar soft surface structure in electromagnetics around the horn antenna is introduced so as to suppress the propagation of surface waves inside the radome and thus improve the gain performance. The simulated results indicate that more than 9 GHz bandwidth of -10 dB return loss and a gain of 12.56 dBi in the radiation direction at 0θ= ? are obtained.
关键词： horn antenna,soft surface,Antenna-in-package (AiP),low-temperature co-fired ceramic (LTCC),radome
更新于2025-09-04 15:30:14
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Effects of sintering process on the structural, dielectric and optical absorption properties of KNbO <sub/>3</sub> -based ceramics
摘要： The influence of the sintering temperature and the dwell time on the structural, optical and dielectric properties of [KNbO3]0.8[Ba(Ni0.5Nb0.5)O3?δ]0.2 ceramics (KBNNO) was systematically investigated. X-ray diffraction measurements of the ceramic bodies sintered at different temperatures indicated that all samples presented a cubic-like structure. However, the results remarkably revealed that both the sintering temperature and the dwell time are crucial factors that must be taken into account for “tuning” the optical response of the KBNNO ceramics. It was concluded that fine distortions in the (Nb,Ni)O6 octahedral site, induced by sintering temperature and dwell time, promoted subtle changes in the local crystal field and, consequently, in the optical properties of the KBNNO. The mechanisms responsible for the observed spectral features of KBNNO were discussed by considering absorbance spectra of NiNb2O6 ceramics and allowed ligand-field transitions. The comparison between both optical spectra revealed a notable similarity between them. Since the octahedral site in KBNNO is equivalent to the nickel columbite structure, it was inferred that the spectral behavior is mainly driven by the same two contributions: one major associated to a distorted octahedral configuration and one minor related to spin-orbit coupling effects. In accordance with X-ray diffraction data, the temperature dependence of the dielectric properties corroborated that the KBNNO present a cubic-like phase in the whole temperature range investigated.
关键词： Ferroelectrics,Ceramic processing,Optical properties
更新于2025-09-04 15:30:14