Study of the Dielectric Behaviour of Cr-Doped Zinc Nano Ferrites Synthesized by Sol-Gel Method

The series of Cr-Zn nano ferrites having the general composition CrxZnFe2-xO4 (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystalline form using the sol-gel method. The samples were sintered at 900°C for 3 hours. The effect of chromium substitution on dielectric properties of Zn-ferrites is reported in this paper. The analysis of XRD patterns revealed the formation of single phase cubic spinel structure for all the Cr-Zn ferrite samples. The FTIR spectra show two strong absorption bands in the range of 400 - 600 cm-1, which corroborate the spinel structure of the samples. The average grain size was found to be in the nanometer range and of the order of 43 - 63 nm obtained using TEM images. The lattice parameter and crystallite size decrease with increase in Cr concentration (x). The investigation on dielectric constant (ε'), dissipation factor (D) and ac conductivity (σac) was carried out at a fixed frequency 1 kHz and in the frequency range of 100 Hz to 1 MHz at room temperature using LCR meter. The plots of dielectric constant (ε') versus frequency show the normal dielectric behavior of spinel ferrites. The value of ac conductivity (σac) increases with increase in frequency for all the compositions. The appearance of the peak for each composition in the dissipation factor versus frequency curve suggests the presence of relaxing dipoles in the Cr-Zn nano ferrite samples. It is also found that the shifting of the relaxation peak towards lower frequency side with an increase in chromium content (x) is due to the strengthening of dipole-dipole interactions. The composition and frequency dependence of the dielectric constant, dielectric loss and ac-conductivity are explained based on the Koop’s two-layer model, Maxwell-Wagner polarization process, and Debye relaxation theory.

Effect of Bi3+ Ion Substitution on Magnetic Properties of Cobalt Nano Ferrites Prepared by Sol-Gel Combustion Method

Bismuth substituted cobalt nano ferrites with the chemical composition Co Bix Fe2-x O4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method. The phase identification of prepared samples is characterised by X-ray powder diffraction (XRD) method, which confirms the formation of a single phase fcc spinal structure. The mean crystallite sizes of all prepared samples were obtained within the range of 21 (±5) nm. Transmission Electron Microscopy (TEM) images also confirmed the crystallite size of all the synthesised samples was in nano range. With the effect of Bi3+ ion substitution on spinal cobalt ferrite, the magnetic properties were investigated by using Vibration Sample Magnetometer (VSM). The obtained hysteresis (M-H) curves of all the samples were analysed under the applied magnetic field of range ± 10 K Oe at 300 K. The magnetic properties such as saturation magnetisation (Ms), remnant magnetization (Mr) and coercivity (Hc) values are tabulated, which show a decrease in trend as the bismuth ion concentration increases. This is due to the addition of Bi3+ ion in the place of Fe3+ ion (octahedral site) and hence the Bi3+-Fe3+ ion interaction predominates as compared with the Fe2+-Fe3+ ion interaction. The data obtained from magnetic studies, the variation among the magnetic properties have been investigated for all the prepared samples.

Nano Copper Ferrite Catalyzed Sonochemical, One-Pot Three and Four Component Synthesis of Poly Substituted Imidazoles

A simple, multi component, one-pot method has been reported for the synthesis of poly substituted imidazoles in presence of magnetically separable and recyclable spinel nano copper ferrite as heterogeneous catalyst by the cyclo-condensation of benzil, aromatic aldehyde, ammonium acetate and substituted amines under ultrasonic irradiation. This method of preparation has many advantages compared to those methods which are previously reported in the literature. This methodology offers simple experimental procedure, milder reaction conditions and environmentally benign approach.

Magnetic Nano Cobalt Ferrite Catalyzed Synthesis of 4H-Pyrano[3,2-h]quinoline Derivatives under Microwave Irradiation

A microwave irradiated magnetically separable nano cobalt ferrite catalyzed green method for the synthesis of 4-phenyl-4H-pyrano[3,2-h]quinolin-2-amine and 2-amino-4-phenyl-4H-pyrano[3,2-h] quinoline-3-carbonitrile derivatives through cyclization of aromatic aldehyde, acetonitrile/malononitrile and 8-hydoxyquinoline is developed and presented in this paper. The cubic magnetic cobalt ferrite nano particles were synthesized by sol-gel citrate precursor method and characterized by FT-IR, XRD, SEM and TEM techniques and the structures of the synthesized pyranoquinoline derivatives were assigned by IR, MASS and 1H NMR techniques. The reaction is carried out in a domestic microwave oven with a heat-resistant microwave safe glass container with a lid.

The Electrical and Optical Properties of Zn0.5Li2xMg0.5-xFe2O4 Lithium Doped Nanoparticle Prepared by Coprecipitation Method

In this study, nano ferrite materials were produced to replace costive industrial materials [1]. Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc. Using co-participation method, five nano ferrite samples Zn0.5Mg0.5-xLi2xFe2O4 (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn0.5Mg0.5-xLi2xFe2O4 samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn0.5Mg0.5-xLi2xFe2O4 increased with the increase of Lithium (Li2x). The energy band gap of the Zn0.5Mg0.5-xLi2xFe2O4 samples ranged from 3.28 to 3.12 eV [1]. The extinction coefficient (K) for five samples of Zn0.5Li2xMg0.5-xFe2O4 increased with the increase of Lithium (Li2x) at 338 nm from 0.074 to 0.207. The high magnitude of optical conductivity is (1.34 × 1012 sec-1) and the maximum value of electrical conductivity is 42 (Ω.cm)-1. This may due to the electrical and optical properties of lithium.

Physical Properties Study of Zn_(0.5)Mn_(0.5−x)Li_(2x)Fe_(2)O_(4) Nanoparticle Series that Prepared by Co-Precipitation Method

Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.

Structural,magnetic,and acidic properties of cobalt ferrite nanoparticles synthesised by wet chemical methods

A detailed investigation on the effect of preparation method on the structural,magnetic,and acidic properties of cobalt ferrite nanoparticles prepared by sol-gel and co-precipitation is presented.Citric acid and ethylene glycol were used as gelling agents,while sodium hydroxide and aqueous ammonia were used as precipitating agents.The resulting ferrites were calcined at 450℃ and 750℃.Sharper X-ray diffraction(XRD)peaks were observed for the samples calcined at 750℃,indicating greater crystallinity of the samples calcined at higher temperature.Average crystallite sizes fell in the ranges of 7.1-21.1 nm and 30.4-42.1 nm for the samples calcined at 450℃ and 750℃,respectively.The infrared spectra revealed two main absorption bands,the high frequency bandν1 around 600 cm^(-1) and the low frequency bandν2 around 400 cm^(-1) arising from stretching vibrations of the oxygen bond with the metal in the tetrahedral(A)and octahedral(B)sites in the spinel lattice.Agglomeration of particles was observed in the scanning electron microscopy(SEM)images.Magnetic parameters of CoFe_(2)O_(4) nanoparticles greatly depended on calcination temperature and preparation techniques.Ammonia temperature programmed desorption(TPD)measurements indicated that weak acid sites predominate medium strength sites,while the number of strong acid sites is the least.Cumulative acidity decreased for the samples calcined at higher temperature.The results underline the effect of preparation conditions on the morphology,crystallite size,and magnetic properties of nano ferrites.