Papers by Keyword: Dielectric

Abstract: Composite La_0.88Bi_0.12Mn₀.₈₀Ni_0.20O₃ was synthesized using the conventional solid-state reaction method with sintering temperature of 1200 °C for 12 hours and the dielectric properties investigated. The X-ray diffraction result shows that the composite has a rhombohedral structure with lattice parameter of a = b = c = 5.5136 Ǻ. Scanning electron microscope shows grains with approximately from 0.8 to 5.4 μm in size with presence of voids. The dielectric permittivity, εʹ and dielectric loss, εʺ were measured in the range of 298 K to 473 K where both are temperature and frequency dependent. At 1 kHz to 100 kHz, the εʹ is around 10000 and the dielectric loss tangent, tan δ is below 1.5. The electric behavior of this composite is best represented by Quasi-dc model which consists of two universal capacitors in parallel. Parameters value from the fitting indicated that high correlations of electrons between inter and intra-clusters. The activation energy, E_a calculated from the conductivity of the sample gives a value of 0.116 eV. Vibrating sample magnetometer shows that the La_0.88Bi_0.12Mn₀.₈₀Ni_0.20O₃ has a magnetic coercivity, H_c of 36.109 G and retentivity, B_r, valued 2.7504 x 10^-3 emu/g.

Abstract: In this paper, polycrystal Ga2O3 thin films were grown on crystal n+-Si substrates by solution process. The XRD profile revealed that monoclinic β-Ga2O3 and rhombohedral α-Ga2O3 were coexisting in the film. The solution-process Ga2O3 film exhibited an ultrahigh transmittance (>97%) to a wavelength range of 280 nm~800 nm. The optical bandgap of ~5.0 eV and breakdown field of 4.2 MV/cm of the Ga2O3 thin film was obtained. Dielectric parameters such as capacitance, dielectric permittivity and loss tangent were investigated. It was observed that these parameters have a strong dependence on frequency.

Abstract: This research is concerned with properties of 0.5BZT-0.5BCT through a water based gel casting process by using Ethylene Glycol Diglycidyl Ether (EGDGE) epoxy resin as a gelling agent. A solution of an ammonium salt of an acrylic polymer in water (NH₄PAA) was used as an additive in order to make the dispersion of the powders easier and provide better stability of the slurry and dispersant. The results were found that viscosities of the 0.5BZT-0.5BCT with EGDGE epoxy resin was minimised by the addition of 1.6 wt% of dispersant based on the dried powder weight. The highest green strengths of around 25 MPa were achieved at 30 wt% EGDGE resin content and 44 vol% solids loading. The gel casting samples were studied at sintering temperatures between 1300-1500 °C. The highest values of piezoelectric and dielectric properties corresponded to 0.5BZT-0.5BCT gel casting samples fabricated with a gel casting slurry incorporating 30 wt% EGDGE resin content, 44 vol% solids loading and sintered at 1500 °C, with d₃₃ and ε_r values of 310 pC/N and 2515, respectively.

Abstract: Wide bandgap semiconductor technology has been generating a great deal of attention due to its fundamental advantages in high power electronics. Understanding and effective control of interfacial properties belong to a group of critical issues requiring progress. In this work, we report progress in wide bandgap interface characterization, achieved using photo-ionization of deep traps under a non-equilibrium condition created by corona-charge bias in deep depletion. This characterization capability is demonstrated on oxidized n-type epitaxial SiC with deep interfacial traps invisible in standard C-V. These traps, initially present at high density, are shown to be reduced by half after a wet anneal. The photo-ionization technique is incorporated in commercially available non-contact C-V (CnCV) metrology [1,2] providing a non-invasive, cost and time saving metrology that benefits development research as well as device fabrication.

Abstract: TPG-core IMS concept was jointly explored in this study. Integrating high thermally conductive TPG graphite core into IMS is expected to simultaneously achieve high thermal conductivity from TPG and electrical functionalities from IMS. Nearly 2x thermal conductivity and 30% weight saving was demonstrated on TPG-core IMS compared to conventional Cu-core IMS. Significant junction temperature reduction (11°C) in steady state and power cycling was revealed by the thermal analysis as the result of improved thermal spreading in plane and through the thickness. The study also proved the manufacturability and compatibility of this TPG-core IMS structure to the existing IMS production and power module assembling. The integration of TPG and IMS paves a new packaging route to increase heat load, improve reliability, simplify module design and reduce assembling cost and number of steps.

Abstract: Dielectric properties of Zn substituted cobalt ferrite (Co_1-xZn_xFe₂O₄) magnetic nanoparticles with various Zn concentrations (x = 0.2-0.8) have been successfully investigated. The structure of the prepared samples Co_1-xZn_xFe₂O₄ confirmed to be cubic spinel structure using X-ray diffraction analysis. The crystallite size of the sample was found to decrease with the increase of zinc content from 11.6 nm to 9.8 nm, while the lattice parameters found to increase with the increase of zinc from 8.18 to 8.25 Å. For Zinc x = 0.6 at frequency 5 kHz have the highest real dielectric constant (ɛ') was 678.8 and imaginary dielectric constant (ɛ'') was 833.3. The maximum impedance found at zinc x = 0.3 was 138.5. The dielectric constant decrease rapidly with increasing the frequency and then reaches the constant value where the frequency was used from 5-120 kHz.

Abstract: In the proceeding way of material research in the field of manganites, LCMO micro and nanoparticles are synthesized via. the solid-state reaction route, glycine-nitrate combustion method respectively. The phase confirmation is done by XRD, FT-IR technique and the surface morphology viewed by Scanning Electron Microscope (SEM). The energy band gap obtained from Diffuse Reflectance Spectroscopy clearly suggests that the band gap of nanoparticles (2.06eV) is larger than that of the microparticles (1.58eV). Both samples comprise of wide band-gap semiconductor, so the refractive index is calculated using Herve and Vandamme relation. The impedance spectroscopy and dielectric properties of the two samples are studied from room temperature to 100oC over the frequency range 10²-10⁶ Hz. The Cole-Cole plot of impedance is fitted using the RC-Circuit R(Q_gR_g)(Q_gbR_gb)(CR_in). The dielectric property is found to be enhanced in nanoparticles as compared to the microparticles. The findings suggest the nanoparticles be promising candidates in the field of high frequency devices as compared to micro.

Abstract: In this paper, melamine was used as porogen to prepare porous polyimide film by in-situ polymerization. The mechanical properties, thermal properties, dielectric properties, oil content and friction and wear properties of polyimide films with different porosity were investigated. The tensile strength of porous films decreases obviously with increase of melamine content. It shows the lower thermal decomposition temperature and the faster decomposition speed compared with the non-porous film, indicating higher heat exchange rate due to holes in porous films. As the porogen content increases, the dielectric constant decreases significantly, and the film with melamine content of 20 wt.% has the lowest dielectric constant of 2.43. The holes lead to good oil storage performance and the wear rate and the friction coefficient decrease with the increase of porosity. Keywords: polyimide; porous; melamine; dielectric; friction

Abstract: Double rare-earth (La; Sm/Gd) substituted Aurivillius family of Bismuth Layered Structured Ferroelectrics (BLSF) namely Bi_2.6Sm_0.2La_0.2TiNbO₉ (BSLT; sample-A), Bi_2.6Gd_0.2La_0.2TiNbO₉ (BGLT; sample-B), single phase ceramics were prepared by solid state route. In addition, intergrowth (x BSLT - (1-x) BGLT, where x=0.49; sample-C) and solid solution (BSLT_­x - BGLT_y; where x + y=0.4; sample-D) materials were prepared. Dielectric, ferroelectric and Raman spectroscopic properties were studied on the said above materials. The X-ray diffraction analysis and Raman spectra revealed well-formation of stable structure. Though, the sample-C and sample-D have lower coercive field, compared to the sample-A and sample-B, but they exhibited sharp hysterisis loop. Therefore the instrinsic defects of sample-D inhabits more sensitivity towards the ferroelectric behaviour. The results were corroborated to the impedance and dielectrical data. The results were consistent with the SEM micrographs and complex impedance plots. An attempt is made to understand the effect of rare-earth ions on A-site of layered-pervoskite structure, defined as: (Bi₂O₂)²⁺(A_n-1B_nO_3n+1)^2-.The term n represents number of pervoskite blocks interleaved with the bismuth oxide layers.

Abstract: Alternating-current powder-based electroluminescence is currently the only technique for quick and easy preparation of large area, low cost electroluminescent panels by the means of material printing. Manufacturing of the panels is currently done exclusively by screen printing which is associated with deposition of much thicker layers than typical for other methods of material printing. Typical thickness of layers is in the order of tens of microns and more. The overall thickness of films forming the panel is however a serious shortcoming of the devices because the driving voltage for generation of light needs to be high and the thickness of layers render the panel non transparent from the side of the dielectric layer. One layer of dielectric films screen printed from the commercially available formulation is approximately 10 μm thick and cannot be effectively reduced anymore and thus another printing technique needs to be exploited. The goal of this work is to define and optimize a composition of a novel ink jet printing formulation of dielectric film and verification of parameters of the final layers for use in this type of technology. The major benefits of ink jet printed dielectric layer are the possible preparation of a panel emitting light from both sides with reduced driving voltage needed for its operation.