<b>Effect of Cerium Ion on Microstructure and Dielectric Properties of Ni-Zn Ferrites Prepared by Solid State Reaction Method</b>

Manganese ferrite (MnFe2O4) has been successfully synthesized by using co-precipitation methods with a various particles size of 13.1, 13.8, 16.2, 18.1, and 18.4 nm. Analysis of crystal structure properties which has been carried out by using XRD (X-Ray Diffraction) method revealed that all samples belong to cubic spinel structure. The measurement used computerized impedance spectroscopy system in the frequency range of 10-120 Hz. The real dielectric constant (ε′), imaginary dielectric constant (ϵ”), and impedance (Z) were determined at room temperature as a function of frequency. The dielectric constant (real and imaginary) and impedance decreased with frequency up to 70 kHz, and then it was constant at a frequency more than 70 kHz. The dielectric properties depending on the crystal structure are also investigated, it consists of the degree of crystallinity, lattice parameter, strain, X-ray density and the impurities of the sample. In the range of grain size of 13.1-18.4 nm, the real (ε′) and imaginary (ϵ”) dielectric constants, and loss tangent increased with the increase of the grain size. In addition, impedance (Z) decreased with increasing grain size. The dielectric constant was found to be the highest for MnFe2O4 with a particle size of 18.1 nm because of low strain value of 0.028 and high X-ray density value of 5.11. Therefore, a sample with the highest dielectric properties is a sample with grain size of 18.1 nm with real dielectric constant of 311; imaginary of 118; and impedance of 328 kΩ at 10 kHz. The frequency variation of (ϵ′ and ϵ”) is explained by Knop phenomenological theory and hopping of electrons between Fe2+ and Fe3+ on octahedral sites.

This study investigates the effect of glass waste powder content on the UV–Vis spectroscopy of polyvinyl alcohol (PVA). The glass powder was obtained from the waste of fluorescent tubes. The solution casting method was utilized to prepare PVA- glass composite films by adding glass powder with 10, 20, 30, and 40 wt. %. UV–Vis absorption spectra of PVA- glass samples were recorded in the range 220–1100 nm. The optical parameters were calculated as follow: absorbance, absorption coefficient, transmittance, refractive index, extinction coefficient, dielectric constant, and imaginary dielectric constant. Based on the XRD results, it is revealed that the PVA become more amorphous with increasing amount of glass waste. UV–Vis spectroscopy studies demonstrated that, for all samples, the absorbance, absorption coefficient, extinction coefficient, and Ei increases with the increase in the amount of glass waste. On the other hand, transmittance decreases with increasing amount of glass waste. The change of the studied properties with wavelength depends strongly on the amount of glass waste powder. At visible region, the transmittance is stable with increasing wavelength for samples containing 20, 30 and 40%. Glass waste, while the pure sample and the sample containing 10% glass waste, the transmittance increases with the wavelength. On the other hand, the absorbance and absorption coefficient for all samples decreases rapidly up to a specific wavelength and then the change is very slight at longer wavelengths. Also, the increase of extinction coefficient and imaginary dielectric constant with wavelength is related to the amount of glass powder added. The change of dielectric constant and refractive index with wavelength depends on the amount of the filler, where the pure and the sample filled with 10% glass powder show normal dispersion, while the other samples show anomalous dispersion. Finally, the pure sample had the highest energy gap (5.7 eV) while the sample containing 30% glass powder had the lowest value (4.8 eV). Through this study, it become possible to change the optical properties of PVA by adding glass waste powder, which allows the possibility of benefiting from the new composites to be used in different applications according to their response to different wavelengths. From an economic and environmental point of view, these wastes can be utilized instead of being thrown away by reusing them as polymer fillers, taking into consideration the change in the optical properties of the matrix polymer.

La3+-substituted β-ferrite: Investigation of structural, dielectric, FTIR and electrical polarization properties

Dielectric properties of Mn0.5Zn0.5Fe2O4 nanoparticles (NPs) encapsulated by polyethylene glycol (PEG) has been studied as a function of frequency in the range 5 kHz to 120 kHz at room temperature. PEG-encapsulated Mn0.5Zn0.5Fe2O4 NPs were synthesized by co-precipitation method with various PEG concentration. X-ray diffraction (XRD) pattern confirmed that Mn0.5Zn0.5Fe2O4 NPs have cubic spinel structure. The crystallite size of the sample was 12.5 nm and then decreased with the increase of PEG concentration. It is due to the agglomeration reduced after PEG encapsulation. The real dielectric constant (ϵ′) of the sample was 320.2 and decreased with the increase of PEG concentration, it is expected because of a decrease of crystallite size. The imaginary dielectric constant (ϵ′) and loss tangent (tan δ) of the samples have a value 360.2 and 1.1 respectively and decreased with the increase of PEG concentration, which is due to the decrease in drift mobility of electric charge carries. The AC conductivity (σ) of the sample was (1.1 × 10-4) kΩ-1 and decreased with the increase of PEG concentration, this may be due to the change in cation distribution of the sample. The capacitance of the sample was (4.5 × 10-11) Farad and decreased with the increase of PEG concentration, it is also caused by the decrease of crystallite size. Furthermore, the real dielectric constant (ϵ′) and imaginary dielectric constant (ϵ′) of the samples have a value 521.1 and 393.8 respectively and decreased with increasing applied frequency; it is due to the fact that above certain frequencies the electronic exchange between the ferrous and ferric ions does not follow the applied field. The AC conductivity of the sample was (2.1 × 10-4) kΩ-1 and increased with increasing applied frequency, contrary the capacitance (C) of the sample was (1.3 × 10-10) Farad and decreased with increasing applied frequency. This can be attributed to the conductive grains become more active at the higher frequency, hence increasing the hopping frequency of electron Fe3+ and Fe2+ ions. The refractive index (n) of the sample was 24.2 and increases with the increase of dielectric constant at low frequency.

These ferrites had been considered very highly valuable electronic materials for many decades. The ferrite compounds have a hexagonal structure. Nano structural and dielectric features for BaFe12-xLaxO19 (0.00, 0.25.0.50, 0.75, 1.00) nano Hexaferrite (NHFs) was studied present research. The Ba NHF prepared via sol-gel technique. The single phase of barium Nano Hexaferrites of various sample was confirmed by XRD, the average crystalline size calculated in the range of 5 to 13 nm.The lattice parameter lattice constant, X-ray density, bulk density, micro strain and lattice strain are the parameters of XRD which are also calculated. The different parameters of XRD also show the decreasing and increasing trend which is totally depend on the concentration. The hexagonal structure also confirmed by FTIR. There are two frequency band are investigated which are ?1 and ?2 which are associated with tetrahedral stretching band and octahedral stretching band respectively. The different frequency band are calculated at different frequency like ?1=500 to 540 and also ?2 = 413. The dielectric properties also measured in the frequency range from 1 MHz to 3 GHz. There are many others parameters are calculated in dielectric properties such as real and imaginary electric modulus, real and imaginary impedance, dielectric constant, dielectric loss and tangent loss. The parameters of dielectric also showing decreasing and increasing in trend. The real and imaginary impedance plot changes as when the frequency increases, the all the specimens converge on one another, and at a higher frequency, the impedance exhibits coherent nature, which is due to the discharge of space charges.

The nature of engineering technique has a significant effect on the particle size, particle distribution and thus affects the morphological, electrical and dielectric properties of the materials. In this work, ZnCr2O4, MnCr2O4, CuCr2O4 and FeCr2O4 nanoparticles have been synthesized using wet chemical based sol–gel auto-combustion method. The crystal structure, lattice constant, unit cell volume, X-ray density and porosity of the calcined powder samples were determined from the data obtained from X-ray diffractometer. Morphology, grains size and distribution of the grains were analyzed using field emission scanning electron microscopy. Dielectric response of the samples was checked in the frequency range of 20 Hz to 20 MHz. The analysis of real and imaginary dielectric constant and tangent loss revealed a non-linear dielectric behavior of the spinel oxides. A strong frequency dependent response of different electroactive regions was found by impedance spectroscopy. Hopping of charge carriers in the conduction mechanism of spinel chromites was analyzed from the variation of ac conductivity with frequency.

Structural, magnetic and dielectric properties of Yb3+ doped BaCo-X hexagonal nanoferrites

Here, we report the synthesis, characterizations and magnetic properties of Ce-Al co-doped nickel ferrite. The samples of pure nickel ferrite ( NiFe2O4 ) and Ce-Al doped nickel ferrite (NiFe1.96Ce0.02Al0.02O4 ) were prepared in nanocrystalline form using sol-gel auto combustion method. X-ray diffraction technique was employed to know the phase purity and for the determination of structural properties. Examination of XRD pattern shows the presence of those reflections which belongs to cubic spinel structure indicating the formation of single phase cubic spinel structure. The lattice constant, X-ray density and other structural parameters were determined from the XRD data and the influence of Al-Ce doping is studied. It is observed from structural studies that the lattice constant and other structural parameters increased. as compared to pure nickel ferrite. The magnetic properties were studied at room temperature using pulsed field hysteresis loop technique. The M-H plot show typical ferrimagnetic behaviour from which the values of saturation magnetization, coercivity and remanence magnetization were obtained. The magnetic data suggests that, Al-Ce co-doping strongly influences the magnetic properties also. The doping of Ce-Al in nickel ferrite leads to canted spin structure. The observed magnetic bahaviour of Ce-Al doped nickel ferrite is explained on the basis of Neel’s and Yafet-Kittel model.

Dielectric properties of ZnxNi1-xFe2O4 magnetic nanoparticles (MNPs) with various Zn concentration (x = 0.2-0.8) have been investigated over a wide frequency range 5–120 kHz. Zn-Ni ferrite MNPs have spinel cubic structure. The crystallite size of the sample for x = 0.2 was about 21.5 nm and then decreases by increasing Zn concentration. For sample with x = 0.4 at frequency 20 kHz, the real dielectric constant ( ) was 35.9, imaginary dielectric constant ( ) was 20.4 and loss tangent ( ) was 0.6. Zn concentration would affect to availability of ferrous and ferric ions in the octahedral site which are preferentially occupied by Zn2+ ion. The dielectric constants decrease with increasing frequency. The sample with at x = 0.6 has the highest dielectric on frequency 5 kHz. The maximum AC conductivity ( ) was 1.7 10-4 Ω-1 at 65 kHz observed for concentration x = 0.3. The dielectric constants and conductivity at low frequency are due to the existence of grains boundary while the dispersion in the high frequency region are due to the conducting grains.

Structural, dielectric, thermoelectric, and magmatic properties of Er3+ ion substituted Mg-Zn spinal nanoferrites: High charge-storage capacitors and high-frequency microwave device applications

Structural, magnetic and dielectrical properties of Al–Cr Co-substituted M-type barium hexaferrite nanoparticles

Synthesis and Characterization of Polypyrrole/ Praseodymium Calcium Manganite Oxide Nanocomposites

Using the real and imaginary dielectric constants of a GaAs/AlGaAs quantum well, both the absorption and refractive index of the structure were calculated. The imaginary dielectric constant was obtained by finding the contribution from each critical point in the density of states. The Kramers-Kronig transform of each contribution gave the corresponding real dielectric constant and these contributions were summed to give the material's total real dielectric constant. Absorption was found from the imaginary dielectric constant and fitted to experimental spectra. All contributions from confined and continuum transitions were considered in the subsequent calculation of refractive index with the resulting spectrum being comparable to published data.

A new class semi-organic nonlinear optical materials: Mono(4-sulfo benzene aminium) tri nickel(II) bis(dihydrogen phosphate) for photonic applications

(YBa2Cu3O7) and (Y3Ba5Cu8O18) superconducting materials were synthesized using auto- combustion method and then sintering at 850°C for 24 hours. The structural properties of the resulted compounds were studied by means of X-ray diffraction (XRD) and the results confirmed the formation of the orthorhombic structure. The lattice parameters (a), (b), and (c) and the crystallite size of the synthesized compounds were calculated using the d-spacing values, Debye Scherrer equation and Williamson-Hall methods. The grain size of the synthesized (YBa2Cu3O7) and (Y3Ba5Cu8O18) compounds was also measured using the scanning electron microscope (SEM). The electrical properties represented by the relationship of the frequency with the real dielectric constant, imaginary dielectric constant, conductivity and the loss factor was determined using the (LCR)Meter and show. The results showed that the optimum value of the superconducting critical temperature (Tc) was found to be higher than 100 Kelvin for both compounds sintered at 850 ° C.