Papers by Keyword: Dielectric Constant

Abstract: Lead Zirconate Titanate (PZT) film was synthesized by sol-gel technique on a silicon substrate. The raw materials used to synthesize the solution of PZT consist of lead acetate, zirconate nitrate and titanate (IV) isopropoxide and 2methoxy ethanol is used as a stabilizer for Ti structure. Acetic acid is the solvent used to solve lat acetate and zirconate nitrate. The XRD pattern of the sample shows that the film has a tetragonal phase with a perovskite structure. FESEM revealed the surface morphologies and the cross-section of the film. The different thicknesses of film and annealing temperatures are investigated in this work. The dielectric constant was measured at 1 kHz, PZT films have a dielectric constant value ( 312-552 ) and a dielectric loss (0.02-0.08) at ambient temperature. Keywords: PZT film; Lead zirconated titanate; ferroelectric properties; dielectric constant.

Abstract: Barium Titanate (BT) is one of the most intriguing ferroelectric materials widely exploited both for academic and technological utilization. The study aimed to investigate characteristics of BT ceramics Synthesized by co-precipitation (BT-C) and solid-state methods (BT-S) with variation of sintering temperatures. Here, the sintering temperatures are 900°C, 1000°C, 1100°C, and 1200°C for 4 h of each The characteristics are microstructure, morphology, and dielectric properties evaluated using X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), and Inductance-Capacitance-Resistance (LCR) meter, respectively. As results, the XRD patterns shows a pure perovskite single phase of BT was obtained by solid-state method at sintering temperature of 1000°C. While, the same result was obtained by co-precipitation at sintering temperature of 1100°C. The average crystallite size of BT-C and BT-S ceramics are in close values and getting larger with the higher sintering temperatures. Meanwhile, tetragonality of the BT-C tends to be larger as compared to the BT-S. The morphology results revealed big formed particles agglomeration (>5 μm) of the BT-C ceramics and the densities proportionally increased as the higher temperatures exhibited less porosity of ceramics. Meanwhile, the BT-S grains were visible and agglomerated in a much smaller size with the density values were different as the change of the sintering temperatures. The dielectric permittivity of the BT-C and BT-S ceramics were increased with higher sintering temperature. Further, the BT-C ceramics possessed higher permittivity than the BT-S due to high densities (less porosity) of ceramics. The highest permittivity of 1150 at 40 kHz was achieved by BT-C at 1200°C.

Abstract: The features of the dependence of the dielectric constant and the specific volume resistance of the composite "80 wt. % SKI-3 + 20 % wt. % LDPE" from the content of nanosized filler particles - aluminum and black carbon. The use of modern methods for studying macroscopic properties and electron microscopy made it possible to study the structure and morphology of the supramolecular formations of the composite. Models and possible physical mechanisms leading to extreme changes in εʹ and ρ_V at low concentrations of nanoparticles are presented.

Abstract: BiScO₃-xPbTiO₃ (BS-PT) of perovskite type structure (with x~0.64) were prepared by solid state ceramic process with addition of calcium fluoride (CaF₂) in different molar ratios (0.5, 1.0 and 4.0 mol%). The doped compositions were found to have different symmetry compared with parent material. The 0.5 mol% doped sample was found to possess enhanced rhombohedral phase as compared to other compositions while he Curie temperature (T_c) was not affected appreciably. Small dielectric peaks were observed, indicating phase transition, at temperature lower than T_c in all the samples except 4.0% doped composition. At room temperature doping reduced the loss factor. d₃₃ and P_r reduced rapidly with doping. The characteristics of BS-PT ferroelectric ceramics became harder with the addition of CaF₂.

Abstract: Nowadays, the usage of blowing agent in polyurethane preparation has been an essential enhance the characterization of polymers or composites material. The use of blowing agent may affect the properties of the materials and directly alter the performance of resulting product. In this paper, the effect of a blowing agent on dielectric properties of palm oil-based polyurethane (POlyOP) have been studied. The palm oil-based polyurethane ( POlyOP) has been prepared using the presence of water act as a blowing agent and tegostab 8486 act as a surfactant. The Oil Palm Empty Fruit Bunch (EFB) was used in the composite as filler. The dielectric constant and loss factor analysis in this study was carried out by Vector Network Analyzer (VNA) at x-band frequency using Nicholson-Ross-Weir (NRW) technique. The dielectric study of PolyOP composite showed that the presence of blowing agent in composite enhance the value of dielectric properties of composite at x-band frequencies.

Abstract: In this study, influence of nanoparticles size on optical and dielectric properties of TiO₂ nanoparticles is investigated through thermal treatment of hydrous amorphous titania synthesized by chemical precipitation method at temperatures 300 °C and 600 °C. The average sizes of nanoparticles estimated respectively are ~ 8 nm and ~ 22 nm. Although the optical bandgap energy of both samples remains the same the E_g Raman mode observed at 144 cm^-1 for bulk TiO₂ is shifted to 150 cm^-1 only for nanoparticles calcined at 300 °C. The shift is ascribed to the size as well as higher density of surface defects. Moreover, the presence of surface defects like oxygen vacancies which provide effective sites for catalytic reaction are confirmed by EPR and photoluminescence studies. The oxygen vacancies enhances space charge polarization and consequently results in higher dielectric constant. In addition, the peak shift of loss tangent which determines the mobility of charge carriers is found to be size dependent. Hence calcination temperature has significant influence on defect levels which in turn determine the optical and dielectric properties of TiO₂ nanoparticles.

Abstract: Strontium hexaferrite is a material of choice due its various magnetic applications. Energy losses are a prominent issue in these magnetic materials. To lower these energy losses, we need to improve the resistivity by reducing eddy current losses. In this work nanoparticles of Gadolinium (Gd) doped Sr-hexaferrite (SrFe_12-xGd_xO₁₉ x =0 .0, 0.1) have been synthesized by co-precipitation method. Structural analysis was done by using X-ray diffraction technique (XRD). It was found that the formation of single phase i.e. hexagonal structure has been achieved when the samples were sintered at 920°C for 20 minutes. AC electrical properties such as conductivity (𝜎_ac), dielectric constant (ε′), dielectric loss (tanδ) and impedance (Z); real (Z') and imaginary (Z") parts have been studied as a function of frequency at room temperature. Aim of the work was to enhance the resistivity and was successfully achieved. Gd doped sample is proposed as an energy efficient material to be used in devices working at high frequencies.

Abstract: Zinc aluminate (ZnAl₂O₄) samples were prepared using nanomilling based solid state reaction method for several potential applications. Effect of milling frequency on structural and dielectric behavior of ZnAl₂O₄ has been explored systemically. Investigation of crystal structure reveals that change in lattice parameter by milling does not alter the cubic lattice of ZnAl₂O₄. This milling frequency at the nanosize resulted in a gradual decrease in the particle size, which can be attributed to the inhomogeneous defects. Grain size in nanometers has been calculated by XRD using Debye-Scherrer formula. Dielectric measurements performed in the range of 20Hz-20MHz confirms the Maxwell –Wagner two layer model which is consistent with the Koop’s theory. High value of ac conductivity indicates that milling blocked the ionic transport. As a result of Nyquist plots, a single semicircle was obtained which indicated the leading role of grain (bulk). The variation in the semicircle radii for different samples is due to the influence of milling frequency.

Abstract: Carbon nanotube (CNT) interconnects are emerging as the ultimate choice for next generation ultra large scale integrated (ULSI) circuits. Significant progress in precise growth of aligned CNTs and integration of multiwalled CNT interconnects into a test chip make them promising candidates for future nanoelectronic chips. Tremendous research efforts were made on silicon based ultra-low-k dielectrics for Cu interconnects, but, the most recent advancements in polymer based composites as dielectric materials open up fresh challenges in the use of low-k dielectrics for CNT interconnects. This paper reviews the emerging polymer composites like Boron Nitride Nanotubes, Graphene/Polyimide composites, Metal Organic Frameworks and small diameter CNTs. Many reviews are already exists on the synthesis, fabrication, dielectric, mechanical, chemical and thermal properties of these materials. In this review, we have explained the specific properties of these materials and the necessities for integrating them into CNT interconnects to meet the requirements of future IC designers.Keywords: low-k dielectric materials, ultra low-k dielectrics, carbon nanotubes, interconnects, dielectric constant,

Abstract: Barium strontium calcium titanate is a dielectric material exploited in fabrication of electronic devices such as capacitors, signal filters and satellite components. Dielectric properties can be enhanced through compositional and microstructural control. This study, therefore, aimed at synthesizing barium strontium calcium titanate (Ba_0.05Sr_xCa_0.95-xTiO₃, where x = 0, 0.225, 0.475, 0.725 and 0.95) powders by a solution combustion technique. The powders were pressed, sintered at 1450°C and tested for their properties. Experimental results revealed that strontium content did not significantly influence chemical composition, particle sizes and density. All powders exhibited a single phase corresponding to Ba_0.05Sr_xCa_0.95-xTiO₃ with fine particles with the average size smaller than 0.4 micrometer. All sintered samples had density higher than 95% of theoretical density. On the contrary, the results indicated that strontium content affected grain size, grain morphology and dielectric constant of the sintered samples. The highest dielectric constant of 531 (at 1 MHz) was achieved in the Ba_0.05Sr_0.225Ca_0.725TiO₃. Dielectric constant was discussed with respect to microstructure.