Search results for " Dielectric"
showing 10 items of 67 documents
Broadband Dielectric Spectroscopy of PSN-Rich PMN-PSN Ceramics
2008
The broadband dielectric permittivity of ordered 0.1PMN-0.9PSN and disordered 0.2PMN-0.8PSN ceramics was investigated. The anomaly of dielectric permittivity is clearly seen in the region of 370 K for 0.1 PMN-0.9 PSN at all frequencies. 0.2 PMN-0.8 PSN shows relaxor behaviour with huge frequency dispersion below 350 K. Calculated distribution of relaxation times shows noticeable influence of polar nano regions to the total dielectric spectrum below 320 K with the longest relaxation times edge diverging according to the Vogel-Fulcher law. In 0.1 PMN-0.9 PSN two a little overlapped peaks present in the distribution of relaxation times, influenced by displacive lead motions at high frequencies…
Broad Distribution of Relaxation Times in 0.6PMN-0.4PZN Relaxor Ceramics
2007
In this paper dielectric spectra of 0.6PMN-0.4PZN ceramic obtained from broadband dielectric spectroscopy is presented. Measurements revealed an unusual relaxor like nature. Two different processes in the dielectric spectra have been observed. High frequency, or short relaxation times, behaviour is typical for ferroelectric crystals. Longest relaxation times do not follow Vogel—Fulcher dependence, which is unusual for relaxors.
Optimization of anodizing process of tantalum for Ta2O5-based capacitors
2020
Anodic oxides were grown to 50 V on Ta in several organic ions containing anodizing baths. Their properties were compared with anodic Ta oxide film grown to the same formation voltage in 0.1 M NaOH. Anodizing process carried out in sodium citrate led to the growth of the anodic oxide with the best blocking properties whilst, when Ta is anodized in sodium adipate, a significant part of the circulated charge is wasted in side reactions, such as oxygen evolution. Photoelectrochemical measurements showed the presence of optical transitions at energy lower than the band gap for the anodic films grown in citrate and tartrate electrolytes, attributed to localized electronic states located close to…
Electric breakdown of dielectric thin films for high-voltage display applications
2016
Smectic A liquid crystal is one of the most promising material for smart glass application due to infinite bistability and low haze at clear state. Voltage is needed to switch from scattering to transparent and it is likely for dielectric breakdown to occur. In order to reduce the probability of dielectric breakdown to occur, a dielectric insulating coating is usually employed. In this work we have compared electrical and optical properties of SiO2 thin films with thickness up to 500 nm coated by flexographic printing and reactive magnetron sputtering. IV characteristics and dielectric breakdown values show sputtered coatings to have higher dielectric strength. For sputtered coatings with t…
A novel flexible approach for prediction and on line diagnostic of partial discharge
2004
Partial discharges (PD), due to unavoidable local defects produced by the industrial manufacturing process, can determine local erosion of the material that may cause the electrical breakdown of the component in which the dielectric material represents the fundamental part. Recently, improved diagnostics of electrical insulation systems by means of electric PD measurements through a stochastic processing of the acquired data have been carried out. In this way, the identification of the defects as well, as the separation of multiple defects simultaneously active, have been performed. In this paper, a novel flexible approach for the on-line characterization of the defects in a dielectric mate…
Anti-Arrhenian behaviour of conductivity in octanoic acid–bis(2-ethylhexyl)amine systems: a physico-chemical study
2015
Pure surfactant liquids and their binary mixtures, owing to the amphiphilic nature of the molecules involved, can exhibit nano-segregation and peculiar transport properties. The structural and dynamic properties of octanoic acid (OA)–bis(2-ethylhexyl)amine (BEEA) liquid mixtures at various compositions have been studied by Wide Angle X-ray Scattering (WAXS), 1H-NMR and broadband dielectric spectroscopy as a function of temperature. It was found that the self-assembly occurs via proton exchange between the OA COOH group and the BEEA NH one; such self-assembled local structures are affected anisotropically by a temperature increase so that the thermal dilatation is more marked in a direction …
Nanostructural depth-profile and field-effect properties of poly(alkoxyphenylene-thienylene) Langmuir-Schäfer thin-films
2008
The correlations between morphological features and field-effect properties of poly(alkoxyphenylene-thiophene) thin Langmuir–Schafer film deposited on differently terminated gate dielectric surfaces, namely bare and methyl functionalized thermal silicon dioxide (t-SiO2), have been systematically studied. The film morphology has been investigated at different film thickness by Scanning Force Microscopy. Films thicker than a few layers show comparable morphology on both dielectric surfaces while differences are seen for the ultra-thin polymer deposit in close proximity to the substrate. Such deposit is notably more heterogeneous on bare t-SiO2, while a more compact and uniform nanogranular st…
Effect of high-k materials in the control dielectric stack of nanocrystal memories
2004
In this paper we studied program/erase characteristics by FN tunneling in Si nanocrystal memories. Starting from a very good agreement between experimental data and simulations in the case of a memory cell with a thin tunnel oxide, Silicon dots as medium for charge storage, and a CVD silicon dioxide used as control dielectric, we present estimated values of the charge trapping when a high-k material is present in the control dielectric. We then show preliminary results of nanocrystal memories with control dielectric containing high-k materials. ©2004 IEEE.
Metamaterial coatings for subwavelength-resolution imaging
2011
Coating lenses are membranes made of materials exhibiting negative index of refraction and deposited on other media with high dielectric constant e 3 . Unfortunately far-field imaging suffers from centrosymmetric aberrations. We propose a simple procedure to compensate partially deviations from ray-tracing perfect imaging in asymmetric metamaterial lenses. We also show that, under some circumstances, coating superlens may recover subwavelength information transmitted in a relative spatial spectrum ranging from 1 to √e 3 .
Research on the electrostatic properties of liquid dielectric mixtures
2007
Abstract This paper presents research results, which confirm the possibility of influencing the electrostatic charge tendency (ECT) of selected mixtures of purely insulating liquids. Tests were performed in a spinning disk system, where the factors influencing the value of the electrification current consisted of variable composition of the toluene–cyclohexane mixture, rotational speed, and a disk diameter. Liquid hydrocarbon mixtures displayed changes in ECT as well as classic insulation parameters such as resistivity and relative permittivity for concentration changes of the admixtures. These results can be used to assist the search for inhibitors of ECT and of aging processes in insulati…