Papers by Keyword: Dielectric Materials

Abstract: This paper presents system performance indices for a class-B power amplifier using Double-Gate (DG) Metal Oxide Semiconductor Field Effect Transistor (MOSFET). It also presents a comparative analysis of three power amplifiers using different switching devices, i.e. Bipolar Junction Transistor (BJT), MOSFET, and DG MOSFET. The MOSFET used in this research work is based on Silicon for n-MOSFET and SiO₂ has been used as oxide layer. These power amplifiers are also being designed and simulated to test the speed and time (taken for each of these power amplifiers) to get the output signal when an input signal is applied. A comparison of these three power amplifier circuits is taken in the tabular form to conclude which power amplifier circuit performs better regarding its switching speed and the time. Switching speed relates with the time taken to amplify the signal, which is the same as its time to amplify the signal to a specific gain. Settling time for these three types of power amplifiers have also been tested and presented for the performance of these power amplifiers.

Abstract: This research work designs a power amplifier with the use of Silicon-based Double-Gate (DG) MOSFET. It is a novel device used to amplify the input signal of an audio signal, etc. This research paper provides information on the problem identification in the existing models and its design objectives with its design constraints. It also reduces crossover distortion due to DG MOSFET instead of BJTs and MOSFETs in the class-B power amplifier. This is a low-power device for the mA range using SiO₂ as a dielectric material.

Abstract: The paper discusses the results of modeling of thermal radio processes for the purpose of non-destructive testing, diagnosis of dynamic states and prediction in dielectrics by sensing electromagnetic self-radiation in microwave hyperspectral mode. Measurement errors when using radiometric methods of testing have been shown. We have found the specifics of reducing measurement error while increasing the dynamics and resolution of radiometric measurements. We have presented a schematic of a new type of hyperspectrometer with higher performance and frequency resolution.

Abstract: Ba_0.985Bi_0.01TiO₃-BaTi_1-xZr_xO₃ powders have been synthesized by two-step soft chemical method to satisfy EIA-X8R specification. Microstructural evaluation conducted by X-ray diffraction and scanning electron microscopy confirms the hierarchical structure of the ceramic grain. The shape of the ε-T curves near the dielectric peak becomes broad with the increase of Zr content. The permittivity of Ba_0.985Bi_0.01TiO₃-BaTi_0.9Zr_0.1O₃ ceramic is ~3000, C/C20 °C is-14.67%, 6.23% and-14.50% at-55°C, 130°C and 160°C, respectively, and the dielectric loss is less than 0.020. This work shows that the two-step soft chemical method is a promising approach for high performance temperature-stable capacitor materials.

Abstract: Small radio frequency identification (RFID) tag antennas are generally designed to achieve conjugate matching with capacitive chips at the called tag resonant frequency. An approximate equivalent circuit is proposed to represent the antenna input impedance in low loss dielectric materials. It consists of a shunt conductance considered to be linearly proportional to loss tangent, an input resistance and reactance of antenna in lossless materials. Comparing with the simulated result of full wave numerical tool, the equivalent circuit gives acceptable errors in input resistance and reactance at the tag resonant frequency and nearby. The simple equivalent circuit can be used to reduce the repetitive simulation work for different loss tangent.

Abstract: Ba_0.6Sr_0.4TiO₃ (BST) thin films were fabricated by solgel technique on Pt/Ti/SiO₂/Si substrate without and with PbO seeding layer from precursor solutions with different concentrations. The crystal structure, surface morphology, dielectric properties and leakage current density of BST thin films are investigated as functions of the concentration of PbO precursor solution. Its found that the growth orientation of BST thin films with PbO seeding layer can be modulated through adjusting the concentration of PbO precursor solution. BST thin film with PbO seeding layer from 0.05 M precursor solution shows the highest dielectric constant and tunability, which may be attributed to the high crystallization and amplitude of the polarization in high (100) preferred orientated films. The leakage current density of BST films increases with the increasing concentration of PbO precursor solution and agrees well with the space-charge-limited current mechanism at room temperature.

Abstract: The CaCu3Ti4O12 and Zr-doped polycrystalline CaCu3Zr0.05Ti3.95O12 were prepared via sol-gel method. Comprehensive characterization including X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with Energy-dispersive X-ray spectroscopy (EDX) were employed to characterize the microstructure, morphology and composition. The dielectric properties of the CCTO based ceramics were studied using impedance analyzer. The results show that replacement of Zr in the Ti- site can achieve the effect of regulation of the dielectric properties.

Abstract: Dispersion plays an important role in aqueous chemical coating process for the preparation of BaTiO3 based next generation BME MLCC powder, since it affects coating coverage and layer morphology of the BaTiO3 particles as well as the microstructure and dielectric properties of the ceramics. In this paper, Poly (acrylic acid-co-maleic acid) (PAM) is used as dispersant, its content influences are carefully investigated. It is known that low content of dispersant leads to not only poor dispersion, low coverage and irregular coating layer of BaTiO3 particles, but also bad temperature coefficient of capacitances and inhomogeneous microstructure of the resultant BaTiO3 ceramics, while excessive dispersant deteriorates the microstructure and performance by reducing the density of ceramic. With proper dispersant content, the particles are dispersed and coated perfectly, finally the dense X7R-satisfied ceramic are obtained with average grain size 103nm and fine microstructure, meeting the requirement of next generation MLCCs.

Abstract: BaTiO₃-(Bi_0.5Na_0.5)TiO₃ (BTBNT) solid solution ceramics with the Curie temperature higher than 150°C were prepared, which were promising for X9R MLCCs application. (Bi0.5Na0.5)TiO3 (BNT) was first synthesized by the conventional solid state reaction and then it was mixed with BaTiO₃ (BT) with increasing BNT content from 0 to 12 mol%. BaTiO₃-(Bi_0.5Na_0.5TiO₃ solid solutions were obtained after calcining at 1100°C. The structural and dielectric properties of BTBNT and Nb-doped BTBNT ceramics were investigated.

Abstract: Two characterization techniques, the steady-state Conduction Current (CC) and the low frequency Dielectric Spectroscopy (DS) are reviewed and compared to each other in order to choose the most suitable method for evaluating the static electrical conductivity (σDC) of an insulating material. In the case of polymeric materials operating above 200°C, the DS appears as being better suited. These techniques are applied for insulating materials identified as good candidates for high temperature (HT) applications and new results are presented. HT polyimide, parylene films and silicon nitride substrates are studied. These examples highlight the σDC magnitudes for temperatures up to 400 °C, as well as other relevant parameters to be taken into account for practical applications.