Chetna Chauhan

Effect of Non-Ionic Surfactant Concentration on Microstructure, Magnetic and Dielectric Properties of Strontium-Copper Hexaferrite Powder

Strontium copper hexaferrite powder with composition Sr2Cu2Fe12O22 was synthesized in presence of a non-ionic surfactant Tween-80 using chemical co-precipitation route. The prepared samples were calcinated at 950 oC for 4 hrs in a furnace and then slowly cooled to room temperature to obtain Sr2Cu2Fe12O22 hexaferrite powder. The effect of surfactant concentration on phase formation, microstructure, magnetic and dielectric properties of Sr2Cu2Fe12O22 were investigated using XRD, SEM, TEM, VSM, dielectric and low field AC susceptibility measurement techniques. The XRD analysis reveals the formation of mixed phases of Y and M type hexaferrites. The synthesized samples exhibited magnetic properties typical for soft magnetic materials, with saturation magnetization typical for Y-type hexaferrites. The dielectric properties were studied within the frequency range 100 HZ to 2 MHz. SEM images show formation of non-uniform, spongy and porous structure. The low field AC susceptibility measurements indicate that formed Sr-Cu hexaferrite powder possesses ferrimagnetic to paramagnetic transition at Curie temperature.

Structural properties of Ba-Zn Hexaferrite prepared by a solvent free method

The W type barium zinc hexaferrite sample was prepared by a solvent free method with and without presence of cationic surfactant CTAB. The precursors were calcinated at 950°C for 4 hrs in a furnace to obtained BaZn2Fe16O27 crystalline ferrite powder. The effect of proportion of surfactant on structural properties of hexaferrite was studied. The hexaferrite powder was characterized by using various instrumental techniques like XRD and SEM. The structural properties of the samples were investigated by using XRD and SEM. The SEM images of the sample in presence of surfactant shows that surfactant controls the morphology of the particles.

Study of microstructural and dielectric properties of Ni substituted BaCo2 hexaferrite prepared by a heat treatment method

Nickel doped barium cobalt hexaferrite samples were prepared using simple heat treatment method. The precursor was calcinated at 650°C for 3 hours and cooled at room temperature in order to obtain barium cobalt hexaferrite. The prepared hexaferrites were characterized by various experimental techniques like Fourier Transform Infrared Spectroscopy (FTIR) and Dielectric measurements. The FTIR spectra was recorded at room temperature using KBr pallet method. The FTIR result confirms the formation of ferrite phase. The dielectric measurements were carried out at room temperature between the frequency ranges of 100 Hz to 2 MHz. The dispersion of real dielectric constant is more at lower frequencies compared to that at higher frequencies, which can very well be explained on the basis of Maxwell Wagner model. The dielectric loss peak is observed at higher frequencies with increase in the cobalt content.

Structural and magnetic properties of BaCo2-xNixFe16O27 hexagonal ferrite prepared by a simple heat treatment method

Barium hexaferrites possess magnetoplumbite crystal structure and have been extensively studied because of their large intrinsic uniaxial anisotropy and high Curie temperature, which make them widely used as permanent magnets, microwave devices and high density magnetic recording media, microwave absorbers, components and shielding [1–3]. Hexagonal ferrites are used in various components at high frequency range due to their high magnetic anisotropy, high Curie temperature, mechanical hardness, very low electrical conductivity, low dielectric loss, excellent chemical stability and corrosion resistance; their magnetic properties arise from the interactions between metallic ions occupying particular positions relative to the oxygen ions in its hexagonal crystalline structure [4, 5]. It is well known that structural and magnetic properties of barium hexaferrites strongly depend upon preparation method, substitution of Fe with other kind of ions and amount [6]. W-type hexagonal ferrites possess seven different sites (4fIV , 2d, 12k, 6g, 4f, 4fV I and 4e) in hexagonal crystal lattice, out of them five are magnetic sites. Iron ions are distributed among these sites of hexagonal crystal lattice [7]. Substitution of divalent or trivalent ions among various sublattices of hexagonal lattice can be used to improve intrinsic magnetic properties of barium hexaferrites [7]. During last decade various efforts have been made to improve structural and magnetic properties of barium hexaferrites by divalent and trivalent substitutions [8–10]. In the present investigation, a simple heat tratment method is adopted to prepare nickel substituted barium cobalt hexaferrite powder. The main objective of present investigation is to study the effect of nickel substitution on structural and magnetic properties of BaCo2−xNixFe16O27 (x = 0.4, 0.8, 1.2, 1.6 and 2.0) hexaferrite powder prepared by a simple heat treatment method and calcined at 650 ◦C for 3 hours.

The structural properties of barium cobalt hexaferrite powder prepared by a simple heat treatment method

The W-type barium hexaferrite was prepared using a simple heat treatment method. The precursor was calcinated at 650°C for 3 hours and then slowly cooled to room temperature in order to obtain barium cobalt hexaferrite powder. The prepared powder was characterised by different experimental techniques like XRD, FTIR and SEM. The X-ray diffractogram of the sample shows W-and M phases. The particle size calculated by Debye Scherrer formula. The FTIR spectra of the sample was taken at room temperature by using KBr pallet method which confirms the formation of hexaferrite phase. The morphological study on the hexaferrite powder was carried out by SEM analysis.

Dielectric Properties of W-Type BaCa2Fe16O27 Hexaferrite Prepared Using a Stearic Acid Gel Route

W-type hexagonal ferrite with composition BaCa2Fe16O27 was prepared using a stearic acid gel method. The precipitate of barium calcium hexaferrite was calcinated at 650°C, 750°C, 850°C and 950°C in a furnace for 4 hours and then slowly cooled to room temperature. The dielectric constants (real Є and imaginary Є), conductivity (σ) and dielectric loss (tan δ) have been measured at room temperature as a function of frequency (102-106 Hz). The dielectric behavior of prepared hexaferrite samples can be explained by the mechanism of polarization and the electrical conduction mechanism is explained by using the electronic hopping model of Heike Johnson.

The Microscopic Magnetic Properties of W-type Hexaferrite Powder Prepared by A Sol-Gel Route

Magnetic particles of W‐type barium‐calcium hexaferrite (BaCa2Fe16O27) have been synthesized using a Stearic acid gel route. The gel precursors were dried at 100° C for 2 hrs and then calcinated at 650° C, 750° C, 850° C and 950° C for 4 hrs in a furnace and slowly cooled to room temperature in order to obtain barium‐calcium hexaferrite particles. The microscopic magnetic properties of prepared samples studying using Mossbauer spectroscopy. Mossbauer spectra of all samples were recorded at room temperature. Mossbauer parameters like Isomer shift, Quadruple splitting etc. were calculated with respect to iron foil. Barium calcium hexaferrite samples heated at 650° C, 750° C, 850° C show relaxation type Mossbauer spectra along with paramagnetic doublet. The intensity of paramagnetic doublet increases with temperature confirm the presence of ferrous ions in the samples, where as sample calcinated at 950° C confirm the presence of ferrimagnetic phase with partial super paramagnetic nature of prepared hexaferri...

Structural and Magnetic Properties of BaMg2Fe10O19 Hexaferrite Particles

BaMg2Fe10O19 hexaferrite particles were synthesized by using a Stearic acid gel method. The prepared Ba-Mg hexaferrite particles were calcinated at Microwave frequency (2.45 GHz, power 900W, 5 min.) as well as at 650°C, 750°C, 850°C and 950°C. Decomposition behavior and the phase associated therein are investigated by means of thermal analysis (DTA, TGA, DSC) and XRD, respectively. The X-ray diffractograms of prepared samples calcinated at 650°C, 750°C, 850°C and 950°C show the presence of M and α- Fe2O3 Phases, whereas the sample heated in a microwave oven shows only single M-phase. Surface morphology of nonporous particles has been examined by using SEM. The samples prepared by conventional heat treatment produces agglomerated clusters of various size particles whereas, the sample heated in a microwave oven shows separate particles with size ranging from 80-240nm. There is significant change in crystallite size of the resultant Ba-Mg hexaferrite particles prepared at microwave frequency. It was observed that heat treatment condition plays a very crucial role in controlling morphology of prepared Ba-Mg hexaferrite particles. Room temperature magnetic measurements were carried out using VSM. Magnetic study reveals that prepared BaMg2Fe10O19 particles possess single magnetic domains.

Temperature Dependent Structural Studies and Magnetic Properties of BaCa2Fe16O27 Hexaferrites Prepared by Stearic Acid Gel Route in Presence of SDS Surfactant

The preparation of BaCa2Fe16O27 hexaferrite powders by a stearic acid gel method with SDS surfactant has been investigated at various sintering temperatures. The samples were characterized by X‐ray diffraction, scanning electron microscopy (SEM), TGA, FTIR and vibrating sample magnetometer (VSM). The effect of sintering temperature on properties of BaCa2Fe16O27 hexaferrites was studied. In presence of sodium dodecyl sulfate (SDS) surfactant, the magnetic parameters, like saturation magnetization, coercivity and remanent magnetization, have been calculated from hysteresis loop.