Abstract:~ 11.88 Å. Oxygenated PrBa2Cu3O7-y samples were found to have an orthorhombic structure with lattice parameter c ranging from 11.72 to 11.75 Å. Electrical resistivity rho(T) measurements performed on these compounds revealed a semiconductor-like behavior in the temperature range 77 <= T <= 300 K. The magnetic susceptibility chi(T) data showed a paramagnetic-like behavior from 5 to 300 K and a clear contribution of the crystalline electrical field (CEF) below 150 K. We have also found an antiferromagnetic order… Show more
“…XRD analysis reveals that lattice parameters and crystallite size increases with the increasing annealing time. Similar trend is also reported by Meza et al [19]. This may be explained as more oxygen atoms are absorbed by the hexaferrite structure with the increasing annealing time.…”
Abstract-Present work deals with the microwave absorption characteristics of BaFe 12 O 19 of interest as radar absorbing material (RAM). There are very few reported works available where particle size has been critically analyzed for absorbing characteristics at microwave frequencies, therefore, in this paper microwave absorption properties of the BaFe 12 O 19 with different particle sizes were investigated. The results showed that the particle size had significant influence on the dielectric and absorption properties of the composites in the 8.2-12.4 GHz frequency range. BaFe 12 O 19 powder of different particle sizes were synthesized by varying the annealing time and it was observed that the real part of permittivity of the composite increases from 5.18 (average value) to 7.50 (average value) and imaginary part increases from an average value of 0.20 to an average value of 2.33, whereas the real part of permeability increases from 0.95 (average value) to 1.11 (average value) and imaginary part of permeability was measured in the range of 0.02 to 0.07. These changes in permittivity and permeability affects microwave absorption application. It is observed that the maximum bandwidth for average particle size of 240 nm is 3.02 GHz and with the increase in average particle size, microwave absorption properties increased.
“…XRD analysis reveals that lattice parameters and crystallite size increases with the increasing annealing time. Similar trend is also reported by Meza et al [19]. This may be explained as more oxygen atoms are absorbed by the hexaferrite structure with the increasing annealing time.…”
Abstract-Present work deals with the microwave absorption characteristics of BaFe 12 O 19 of interest as radar absorbing material (RAM). There are very few reported works available where particle size has been critically analyzed for absorbing characteristics at microwave frequencies, therefore, in this paper microwave absorption properties of the BaFe 12 O 19 with different particle sizes were investigated. The results showed that the particle size had significant influence on the dielectric and absorption properties of the composites in the 8.2-12.4 GHz frequency range. BaFe 12 O 19 powder of different particle sizes were synthesized by varying the annealing time and it was observed that the real part of permittivity of the composite increases from 5.18 (average value) to 7.50 (average value) and imaginary part increases from an average value of 0.20 to an average value of 2.33, whereas the real part of permeability increases from 0.95 (average value) to 1.11 (average value) and imaginary part of permeability was measured in the range of 0.02 to 0.07. These changes in permittivity and permeability affects microwave absorption application. It is observed that the maximum bandwidth for average particle size of 240 nm is 3.02 GHz and with the increase in average particle size, microwave absorption properties increased.
“…It is well known that if Fe or Ba ions is substituted with Co-Ti, Zn-Ti, Zn-Sn, Co-Sn, Ni-Zr and Co-Mo, the saturation magnetization, coercivity, anisotropy constant and ferromagnetic resonant frequency of barium ferrite could be improved [13][14][15][16]. This is one of the serious constraints in an absorbing material, therefore, the relationship between the ferromagnetic resonant frequency of barium ferrite and the substitution elements requires further research [12].…”
The effect of sintering temperature and Mn-Ti (x = 0.1 and 0.5 % mol) doped in Barium hexaferrite (BaFe12O19) on the microwave absorption properties have been investigated. The BaFe(12-2x)MnxTixO19samples were prepared by using a solid state reaction method from technical grade materials of BaCO3, Fe2O3, MnO2, and TiO2. The permagraph and vector network analyzer (VNA) measurement with frequency of 4 – 10 GHz were used to determine the magnetic properties and microwave absorbing properties, respectively. The magnetic induction and magnetizing force (B-H) curve analysis of BaFe(12-2x)MnxTixO19revealed that by increasing the Mn-Ti dopant concentrations, the remanence (Br) and BH(max) increases, meanwhile, the HCBvalue decreases for both 1100 and 1150oC. The frequency dependence of reflection loss (RL) measurement given anoptimum value of-26.15 dB at frequency of 9.18 GHz which obtained by x = 0.1% mol Mn-Ti (1100oC). The maximum absorption peak was achieved for 0.5 % mol Mn-Ti sample with ~98.3 % at 9.18 GHz. By controlling the sintering temperature and Mn-Ti dopant concentration, the RL and absorption behavior can be modified to desirable values and also indicates that higher Mn-Ti dopant concentration (0.5% mol) possess better absorbing characteristics. Furthermore, it was found that complex permitivitty and permeability values of BaFe12O19can be modified by controlling the Mn-Ti dopant concentration.
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