Modulation in Electric Conduction of PVK and Ferrocene-Doped PVK Thin Films

In this article, the dielectric properties of poly (9-vinylcarbazole) (PVK) and ferrocene-doped PVK thin films are studied. The thin films were grown by the isothermal solution casting technique. Dielectric properties of grown films were studied as function of ferrocene concentration, frequency, and temperature. The relative permittivity (ε′) is increased with increasing ferrocene percentage (~1%) due to the free charge carriers. The relative permittivity decreases for higher ferrocene percentage (~2%). However, the relative permittivity of PVK and ferrocene-doped PVK samples remains almost constant for studied temperature range (313–413 K). The frequency dependence of tan δ for all samples is studied. The frequency dependence of dielectric parameter exhibits frequency dispersion behavior, which suggests all types of polarization present in the lower frequency range. The loss tangent (tanδ) values are larger at higher temperatures in the low frequency region. However, the tan δ values at different temperatures are almost similar in the high frequency region. It is observed that the relative permittivity is maximum, dielectric loss is minimum, and AC conductivity is minimum for 1% ferrocene doped PVK as compared to pure PVK and 2% ferrocene doped PVK samples.

Boundary restricted genetic algorithm for multi-layer equivalent dielectric parameters retrieval of artificial gradient structure

With the equivalent dielectric parameters of an artificial gradient structure consisting of a kind of dielectric material as inputs of FDTD multi-layer equivalent simulation, there are big nonuniform differences between the S-curve of retrieval methods and the corresponding full structure. In order to decease these differences, here, a boundary restricted genetic algorithm is proposed. In our method, Smith S method is employed to find the rough values of dielectric parameters, and at the same time, the up and low limit cases are introduced to calculate the boundary parameter values for each layer of the artificial structure and form the searching areas for genetic algorithm to get high-precision inversion of S-curve. The FDTD S-curve of the retrieval parameters and full structure of cone gradient and moth eye were performed experimentally, the maximum deviation of inversion S21 curves corresponding to the cone and moth eye with full structure is limited within 0.0028 and 0.0024 in the X-band (8–12[Formula: see text]GHz) range, respectively, which shows us the promising application of our method in dielectric parameter retrieval and may be helpful for electromagnetic field analysis.

Numerical stability of solitons waves through splices in quadratic optical media

The propagation of soliton waves is simulated through splices in quadratic optical media, in which fluctuations of dielectric parameters occur. A new numerical scheme was developed to solve the complex system of partial differential equations (PDE) that describes the problem. Our numerical approach to solve the complex problem was based on the mathematical theory of Taylor series of complex functions. In this context, we adapted the Finite Difference Method (FDM) to approximate derivatives of complex functions and resolve the algebraic system, which results from the discretization, implicitly, by means of the relaxation Gauss-Seidel method. The mathematical modeling of local fluctuations of dielectric properties of optical media was performed by Gaussian functions. By simulating soliton wave propagation in optical fibers with Gaussian fluctuations in their dielectric properties, it was observed that the perturbed soliton numerical solution presented higher sensitivity to fluctuations in the dielectric parameter β, a measure of the nonlinearity intensity in the fiber. In order to verify whether the fluctuations of β parameter in the splices of the optical media generate unstable solitons, the propagation of a soliton wave, subject to this perturbation, was simulated for large time intervals. Considering various geometric configurations and intensities of the fluctuations of parameter β, it was found that the perturbed soliton wave stabilizes, i.e., the amplitude of the wave oscillations decreases as the values of propagation distance increases. Therefore, the propagation of perturbed soliton wave presents numerical stability when subjected to local Gaussian fluctuations (perturbations) of the dielectric parameters of the optical media.

Electrical Strength and Physicochemical Performances of HTV Silicone Rubber under Salt-Fog Environment with DC Energized

In recent years, the performances of rubber composite insulators, which operate in the coastal foggy regions, have attracted researchers’ concern because of the observation of their degradation. In this paper, salt-fog experiments with DC test voltage of high-temperature vulcanized (HTV) silicone rubber (SR) have been conducted. The electrical strength and material performances of samples with salt-fog treatment were focused on. The DC flashover voltage, hydrophobicity, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and dielectric parameter were investigated. It was found that the samples’ performances deteriorated after salt-fog treatment. The DC flashover voltage of HTV SR decreased in the salt-fog environment. The hydrophobicity of the material deteriorated and the static contact angle (CA) became small. Under the action of electric and thermal stress, the surface of samples after salt-fog treatment became rough and porous. The absorption peak of the hydrophobic groups decreased, indicating that the molecular chain of SR material was broken, and the filler was consumed, bringing down the arc resistance of the sample. The absorption of moisture further led to insulation performance loss and then reduced the electrical strength of the material. Degradation of physicochemical properties will eventually lead to a decline in electrical strength.

NEW WAVEGUIDE METHOD FOR DIELECTRIC PARAMETER MEASUREMENT

Perfect knowledge of dielectric parameters is necessary for its application in various devices. In spite of the whole range of measurement techniques, their practical implementation in the microwave frequency band runs into some difficulties. This article describes a new method for nonmagnetic dielectrics permittivity and loss tangent measurement in the microwave frequency band. A dielectric specimen slab is placed in the short-circuited waveguide section normal to its axis and fills the whole cross-section of the waveguide at approximately quarter wavelength from its short-circuited endpoint. By means of the vector network analyzer the waveguide section reflection factor is measured. Objective function is de-termined as difference between calculated and measured module and phase of the reflection factor. Specific code for ob-jective function calculation and its minimization is worked out. Minimization of this function by varying dielectric parameters makes it possible to find real values of these parameters. The method needs no de-embedding and can be used with non-calibrated waveguide-to-coax transitions. Also it is less sensitive to the noise component of reflected signal. The testing results show that new method’s error does not exceed 0.2 % for relative permittivity and 1% for dielectric loss tangent.

Processing and characterization of Cd/Ti co-substituted BiFeO3 nanoceramics

The aim of the present study is to synthesize the Bi(Cd0.45Ti0.45Fe0.10)O3 (BCTF45/10) nanoceramics by solid state reaction ceramic method at an ambient temperature. Therefore, a raw material in stoichiometric ratios of carbonates and oxide powder was employed to obtain a precursor of the BCTF45/10 nanoceramics. The as-prepared mixture is calcined at 1010 K for 4 h in an air atmosphere. Preliminary structural and surface morphological analyses were carried out using powder X-ray diffractometer and scanning electron microscopy technique, respectively. X-ray analysis of synthesized compound shows the formation of single-phase orthorhombic structure with an average crystallite size of 25 nm. The sintered bodies have relative density above 95%. A correlation between both dielectric parameter of the as-synthesized compounds were also discussed in a wide temperature (298–673 K) and different operated frequency range (1–750 kHz). Addition of Cd/Ti affected the ferroelectric property of the BiFeO3 due to contribution from the leakage current.