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Complex permittivity, permeability and microwave absorbing properties of Co–Ti substituted strontium hexaferrite

100%

Narang S. B. , Kaur P. , Bahel S.

Materials Science Poland

2016

tom Vol. 34, No. 1

19--24

M-type strontium ferrite with compositions SrFe(12-2x)CoxTixO19 (x = 0.0, 0.3, 0.5, 0.7, 1.0), were prepared by two route ceramic method. The effects of Co-Ti substitution on their microstructure, electromagnetic properties, and microwave absorptive behavior were analyzed. The complex permittivity (epsilon'-j epsilon '') and complex permeability (mu'-j mu '') have been measured from 8.2 to 12.4 GHz using a network analyzer. Scanning electron microscope was used to analyze the grain size distribution and porosity of the ferrite. X-ray diffraction confirmed the M-type structure of the doped strontium ferrite. Vibrating sample magnetometer was used to study hysteresis loop of the ferrite. This study suggests that the control of grain size, decrease in coercivity and enhanced values of dielectric constant and loss are effective means to improve microwave absorption. The dielectric constant and loss were enhanced in comparison to the permeability constant and loss over the entire frequency range.

Effect of low oxygen pressure on structural and magnetic properties of quenched SrFe12O19 thin films

100%

Katlakunta S. , Praveena K. , Singh R.

Materials Science Poland

2013

tom Vol. 31, No. 4

581--586

Strontium hexaferrite thin films have been grown on glass substrates at room temperature in oxygen environment by pulsed laser deposition method. The effect of oxygen pressure (pO2) on the structural and magnetic properties has been investigated. The as-deposited films were found to be amorphous in nature. The crystallization of these films was achieved by annealing at a temperature of 850 °C in air. The thickness of the film increased with pO2. The film grown at pO2 = 0.455 Pa had a clear hexagonal structure. The values of coercivity for the films were found to increase with pO2.

Effect of rare-earth co-doping on the microstructural and magnetic properties of BaFe12O19

63%

Güler P. , Ertuğ B. , İpek-Işıkcı N. , Kara A.

tom Vol. 20, nr 3(65)

23--35

Ba0.85(La,Y)0.15Fe12O19 hexaferrite magnets were produced using the powder metallurgy method. The phase analysis of the ferrite magnets was carried out by X-ray diffraction (XRD) technique. A single hexaferrite phase was present in both samples as revealed by XRD patterns. The microstructural evolution in the hexaferrite samples was examined using Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS). The grain morphology altered with the sintering temperature. Room temperature ferrimagnetic hysteresis curves were obtained by Vibrating Sample Magnetometer (VSM). The crystallite size and the lattice parameters (a,c) were also calculated after sintering at 1150ºC and 1250ºC. Saturation magnetizations, Ms were determined to be 48.60 emu/g and 52.95 emu/g for the samples sintered at 1150ºC and 1250ºC, respectively whereas the remanent magnetizations, Mr were 29.26 emu/g and 31.17 emu/g. The coercivity, Hc decreased from 3.95 kOe to the value of 2.44 kOe with the sintering temperature due to the increase of the crystallite size. The squareness ratios (Mr/Ms) of the ferrimagnetic samples were different because the uniaxial anisotropies altered after sintering at 1150ºC and 1250ºC. The maximum energy product, (BH)max dropped from 35.81 kJ/m3 to 27.38 kJ/m3 when the sintering temperature increased. This result can be attributed to a combination of higher magnetization and the lower coercivity.