Papers by Keyword: Dielectric Loss

Abstract: Investigating the dielectric characteristics and structural alterations in XLPE composites, commonly employed in the insulation of covered conductors, stands as a pivotal research focus. In this study, we examined the variation in dielectric loss (tanδ) concerning frequency and voltage, influenced by thermal aging in XLPE insulation. To achieve this, the samples underwent aging at 120°C for six periods, a total of 450 hours. Furthermore, we conducted PD tests, FTIR, and SEM assessments on the insulation both before and after the aging process. A comprehensive analysis of the material's property changes during thermal aging was performed by comparing the PD test results with the tanδ measurements. In order to delve deeper into the interpretation of these findings because of thermal aging, we explored both internal and surface structural modifications, which directly impact tanδ and PD values, utilizing FTIR and SEM techniques.

Abstract: The microwave absorption properties of La_0.85Ag_0.15MnO₃ prepared by solid state method was investigated. Analysis of X-ray diffraction data using a refinement technique confirmed the rhombohedral structure of the samples. The microstructure of the sample characterised from field emission scanning electron microscope micrographs showed irregular grain shapes with grain sizes ranging from 800 to 1500 nm. M-H curves revealed the weak ferromagnetic properties of the sample at room temperature. The real and imaginary parts of permittivity and permeability as well as microwave reflection loss were measured by a vector network analyser in the 8–18 GHz frequency range. The La_0.85Ag_0.15MnO₃ sample showed a minimum reflection loss of –57.2 dB at 16.41 GHz, with a –10dB bandwidth (corresponding to reflection loss below –10 dB, or 90% absorption) of 2.67 GHz. The microwave absorption of La_­­­­_0.85Ag_0.15MnO₃ mainly arises from the conduction loss and domain wall motion which contributed to dielectric loss and magnetic loss, respectively.

Abstract: A variable electric field is applied to a crystal. This field gives rise – through the piezoelectric coupling – to the variable mechanical stresses. Then the dislocations in the crystal will be driven by Peach-Koehler force and will start moving, dissipating the external field energy. Connection of the electric field energy dissipated per unit time with the internal friction is found. The case of resonant loss (Granato-Lucke model) is considered. The loss related to this mechanism to be at frequencies of megahertz range. The relaxation processes being responsible for the Bordoni and Hasiguti peaks also are considered. The use of obtained equations makes it possible to distinguish the dislocation contribution to both dielectric loss and dielectric dispersion and, therefore, to derive additional information about the crystal structure in a sufficiently simple way in terms of only one method.

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: High dielectric constant of CaCu₃Ti₄O₁₂ (CCTO) has drawn a great deal of intention these past years as potential material for capacitor and even micro-electronic applications. In this research, an attempt has been made to investigate the relationship between the calcination temperature and the dielectric properties of CCTO. The calcination of CCTO at lower temperature (below 1000^○C) provides incomplete reaction process, where the secondary phase is detected on the sample. Calcination at 1040^○C provides a single phase as just same with the control sample (sample which had gone through both phase calcine and sinter). It is also found that calcination at 1040^○C provides the dielectric properties that almost the same with the calcine-sinter sample.

Abstract: CaO–B₂O₃–SiO₂ (CBS) glass-ceramics containing ZrO₂ were prepared by conventional melting and heat treated crystallization method. The effects of ZrO₂ on the crystallization behavior, sintering characterization and dielectric properties of the glass-ceramics were analyzed respectively. The results indicated that ZrO₂ addition can improve the crystallization and densification of CBS glass-ceramics. The major crystallized phase of sample with≥7wt% ZrO₂ was cyclowollastonite (α-CaSiO₃).It is found that the optimal sintering condition for the glass-ceramics is 770 ^oC for 30min. CBS glass ceramics sample with 7wt% ZrO₂ shows the best sintering characterization and dielectric properties (ρ= 2.71g/cm³, ε_r ≈8.8,tan δ=2.36×10^-3 at 1 MHz), which is supposed to be suitable for LTCC application.

Abstract: [(K_0.5Na_0.5 )_0.935Li_0.065]NbO₃–Mn ceramics (Mn = 0, 1.50 and 3 mol %) (KNNL–Mn) were synthesized and measured dielectric properties. Which the K₂CO₃, Na₂CO₃, Li₂CO₃, Nb₂O₅ and MnO₂ (0, 1.5, 3 mol%) were mixed by ball milling method and calcined powders at 1,073 K for 4 h and the sintered at 1,343 K for 2 h in air. The crystal structure was analyzed by XRD technique, the crystallite size was identified by Scherrer’s equation and calculated the theoretical density. It was found that, the XRD patterns of the KNNL–Mn ceramics added with Mn contents was indicated the tetragonal structure and. the crystallite size of Mn = 0, 1.50 and 3 mol% about 32 nm, 34 nm and 57 nm, respectively. The physical properties of the KNNL–Mn ceramics was found that the maximum theoretical density of 90.79 % for Mn = 1.50 mol%. The dielectric constant was found to be maximum of 909.77 and dielectric loss of 0.48 for Mn = 3 mol%.

Abstract: Sr - doped NiO ceramic was prepared using solid state method. The calcination temperature used at 950 oC for 4 hours and the sintering temperatures was varied from 1100 to 1300 oC for 3 hours. The results depict the microstructures increasing in grains size (1-8 μm) by increase of sintering temperatures. The density and porosity testing support the result of microstructures analysis. The larger grains size induced the increase in density and lower in porosity. The dielectric properties is observed in a wide frequency range of (1 - 1 000 MHz). The increase of dielectric constant is associated with the decrease of dielectric loss. The optimum sintering temperature was obtained at 1200 oC depict the grain size range (1 - 2 μm) with highest dielectric constant (1.61 x 103) and lowest dielectric loss (1.15) at 1MHz.

Abstract: Lithium ion batteries have become a popular power source for portable electronic equipments. It is found to be superior in gravimetric energy density as it provides about 1.5 times more energy compared to nickel hydride battery. In this study, Polyethylene Oxide based polymer electrolytes were used for investigation. PEO based solid polymer electrolyte films were prepared by solution casting technique with different concentration of salt and different %wt of zirconia nanofiller. The X-ray diffraction analysis was carried out for the identification of compounds available in the sample and to determine the relative concentrations by the intensities of pattern lines. Also the superposition of absorption bands of specific functional groups was confirmed with the infra-red spectrum of FTIR. The Complex Impedance Spectroscopy technique was further used to measure the cell admittance / impedance in a wide range of frequencies and analyzed in the complex admittance/ impedance plane. From the impedance test results it is observed that the conductivity of polymer electrolyte was improved from 7.39×10−4 Scm−1 to 5.24×10−3 Scm−1 after adding 3%wt of ZrO₂ nanofiller with pure polymer. Set up of nano Lab is rare, new and uncommon. It is also an emerging technology. Fabrication of powder needs extra machines which are not popular among common people. It will become popular in the coming future. When particle size is reduced, the quantity of powder is reduced, quality is increased.

Abstract: The high dielectric permittivity of Y₂NiMnO₆ ceramics were measured by Agilent E4294A (Impedance Measurement) range of frequency 100 to 10 MHz in this research. In this sample ceramics, passing by a sintering temperature of 1400°C at 6 hours to 24 hours. The phase and microstructure of the deposited materials were investigated as a function of sintering temperature, using X-ray diffraction (XRD) and scanning electron microscopy (SEM). We found that the dielectric properties are very sensitive to the several sintered follow by time, and high temperature can be related to the change ordering of Ni²⁺ and Mn⁴⁺ ions.