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[IEEE 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Va?ster?s (2018.9.3-2018.9.6)] 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Overview On Functional Materials for Frequency Tunable Antennas
摘要： We report the integration of different kind of materials with improved and adapted properties within antenna designs. In this framework, an overview of three frequency tunable antennas will be presented. Two of them are based on radiating slot elements integrating a Ba2/3Sr1/3TiO3 (BST)-based tunable capacitance and therefore present a continuous tunability for the first one while the second one is integrating a VO2-based switch for a discrete tuning. The third design presented in this paper propose a frequency reconfigurable composite GeTe-metal patch antenna operating at the millimeter-waves (24-30 GHz) whose resonant frequency can be tuned and repeatedly changed upon the application of successive laser pulses.
关键词： Frequency tunable antenna,VO2 switches,BST tunable capacitance,Phase Change Materials
更新于2025-09-23 15:23:52
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Effect of potassium and magnesium codoping on the dielectric properties of BST powders
摘要： K and Mg codoped BST powders were prepared by a sol-gel method, and the effect of doped concentration on the dielectric performances was studied. For comparison, pure, Mg doped and K doped BST powders were studied. XRD shows all powders reveal complete diffraction peaks and ABO3 cubic perovskite polycrystalline structures. Compared to the pure BST powder, Mg doped BST powder shows a little weaker crystallization, 5%～15% K doped BST powders exhibit stronger crystallization, and the crystallization is getting stronger with increasing K doped concentrations from 2% to 15%. BST powder shows lattice parameter of 3.963 ?A, Mg doping corresponds to 3.963 ?A, 2%～20% K doping correspond to 3.963 ?A～3.967 ?A, and Mg and K codoping make lattice parameters increase from 3.967 ?A to 3.974 ?A. Mg2+ ion and K+ ion show acceptor doped mechanisms, Mg doping makes grains refine, and K doping makes grains grow. Pure BST powder and Mg doped BST powder show uniform grains with unclear grain boundaries, K doped BST powders can obtain uniform and dispersive grains with clear grain boundaries, but Mg and K codoping makes the uniformity and dispersity of the powders getting worse. Compared to pure BST powder, Mg doped BST powder shows smaller but more stable dielectric constant and dielectric loss, K doped powders tend to reveal larger and less stable dielectric constants and dielectric losses. Mg and K codoped BST powders show less than 35 dielectric constants, and lower than 0.02 dielectric losses. Dielectric properties are strongly dependent on the crystallization, doped mechanism and morphology. Mg doped and 2% Mg 2% K and 2% Mg 5% K codoped BST powders show low and stable dielectric constants and dielectric losses, thus can meet the requirements for tunable microwave applications and other applications.
关键词： dielectric property,codoping,Mg,K,BST powder
更新于2025-09-23 15:23:52
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Structural and dielectric properties of PLD grown BST thin films
摘要： Thin films of Barium Strontium Titanate (BaSrTiO3, BST) have been deposited on platinised silicon substrate using pulsed laser deposition (PLD) technique. The effect of growth pressure and temperature during the film deposition on the crystallization and dielectric behaviour of the BST films has been studied. The effect of plume dynamics due to variation in deposition parameters present inside the deposition chamber has also been investigated. The dielectric constant of the BST thin film deposited under variable deposition pressures increases with increase in deposition temperature at a frequency of 1 MHz. The BST thin film deposited at 1.33 × 10?4 bar and 800 °C substrate temperature exhibits high dielectric constant (≈475) with 65% tunability which can be efficiently exploited for the realization of tunable resonators and filters.
关键词： Barium Strontium Titanate,BST,PLD,tunability,dielectric properties
更新于2025-09-23 15:21:21
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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) - Characterization and Modeling of Epitaxially Grown BST on a Conducting Oxide Electrode
摘要： This work presents a characterization technique and an EM-model for a thin film BST50 varactor grown on the oxide electrode material SMO, describing the benefits and limits of this characterization technique. Effective capacitance, Q factor, ESR and leakage current are evaluated and analyzed to understand the dominating mechanisms for the overall characteristic. The Q factor for this 13.3 pF varactor is 20.5 at 1 GHz. The extracted permittivity is 365, indicating a good BST crystal quality despite only 80 nm film thickness. The tunability at battery voltage level 3.7 V bias voltage (46 V/μm) is 67.8 %. The EM model shows very high Q factors up to 6 GHz, revealing outstandingly high potential for this oxide varactor with Q factors of up to 70 at 1 GHz, while still maintaining its large tunability. Hence, the ability to epitaxially grow BST on structurally similar SMO allows for very thin BST thicknesses with very low defect density, and thus, very high tunability at very low voltage below 3.7 volts.
关键词： Q factor,EM-model,varactor,BST,tunability,characterization,permittivity,SMO
更新于2025-09-04 15:30:14
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The effect of titanium excess and deficiency on the microstructure and dielectric properties of lanthanum doped Ba0.55Sr0.45TiO3 with colossal permittivity
摘要： The temperature dependent dielectric properties of (Ba0.54875Sr0.44875La0.0025)Ti(1+x)O3 with both an excess and a deficiency of 0.25 mol.% TiO2 were investigated. The samples were prepared by the mixed oxide method and sintered in a conventional oven at temperatures ranging from 1400 °C to 1475 °C. The cubic perovskite structure was confirmed with XRD at room temperature. The sample with an excess of 0.25 mol.% Ti exhibited reduced grain growth while abnormal grain growth was observed for samples without Ti modification. Samples exhibited colossal permittivity for all modified compositions. With a 0.25 mol.% deficiency of Ti a permittivity over 65,000 and a tan δ under 0.05 were measured over a temperature range of -68 °C to 150 °C and a frequency range between 50 kHz and 1 MHz. This paper shows that by fine tuning the composition, materials with new, exciting and widely adjustable dielectric properties can be achieved.
关键词： Doping,Colossal permittivity,Lanthanum,BST
更新于2025-09-04 15:30:14