XRD, DTA AND TGA INVESTIGATIONS OF THE BaFe12-xAlxO19 SOLID SOLITIONS (original) (raw)
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X-ray diffraction studies on aluminum-substituted barium hexaferrite
Materials Letters, 2004
Effect of aluminum substitution in barium hexaferrite was studied following the hydrothermal precipitation -calcination techniques. It was attempted to prepare aluminum-substituted barium hexaferrites with compositions BaAl x Fe 12 À x O 19 having x = 2,4, 6, 8 and 10. The precursors were prepared by using stoichiometric amounts of Ba, Al and Fe 3 + nitrate solutions with urea as the precipitating agent. The hydrothermally prepared precursors were calcined at temperatures in the range of 800 -1200 jC. The detailed work carried out on identification of crystalline phases through XRD revealed that, after the hydrothermal treatment, the samples showed barium carbonate, hematite and boehmite as the crystalline phases (except that boehmite was not identified for Ba/Al/Fe ratio as 1:2:10). Irrespective of the Al content, none of the 1000 and 1200 jC calcined samples showed any crystalline phase of Al. The 1200 jC calcined samples showed that Alsubstituted barium hexaferrite is formed only with the Ba/Al/Fe atomic ratio of 1:2:10. With increase in the Al content, formation of hexaferrite was not observed. BaCO 3 was found be present even at 1200 jC in all the samples except for the one having Fe/Al ratio 5. The normal decomposition temperature of BaCO 3 is between 950 and 1050 jC. It is difficult to explain the increased stability of BaCO 3 , which is perhaps responsible for hindering the formation of aluminum-substituted barium ferrite having Fe/Al ratio V 2. The Al substitution in barium hexaferrite was confirmed through magnetic measurements. D
Structural Analysis Of Ba Y-Type Hexaferrite Samples Prepared By Chemical Co-Precipitation Technic
2018
Y-type hexaferrites BaM2Fe12O22 (where M2 = Cr2, In2, Ti2 selected as trivalent impurity) powders are synthesized by chemical co-precipitation method and subsequent heat treatment at 1000°C and 1100°C for 4 hrs & 6 hrs. The X-ray diffraction measurements results showed that the Y-type hexagonal structure. The X-ray diffraction patterns of the samples annealed at 1000°C & 1100°C for 4 hrs & 6 hrs which manifest that all the species have hexagonal crystal structure with lattice constants of a = 4.31 – 4.56 Å and c = 43.9844.59 Å which is followed from standard values of a 5 Å and c 45 Å . The SEM observation of powder BaM2Fe12O22 sample shows that the microstructures of the compounds are hexagonal. The structural analysis and lattice parameters have been observed from the XRD patterns of the studied all six samples. There are six types of hexagonal compounds M, Y, W, Z, X and U. The preparation of the compounds has been done for the Y-type hexagonal ferrites. The SEM photograph shows ...
Study of the Properties of Co-Substituted Ba2Mg2Fe12O22 Hexaferrites
Proceedings of The 3rd International Electronic Conference on Materials Sciences, 2018
We present results from a study on the influence of the substitution of Mg 2+ cations in the Y-type Ba2Mg2Fe12O22 hexaferrite with magnetic cations, such as Co 2+ , on its structural and magnetic properties. The Ba2Mg0.4Co1.6Fe12O22 powder was synthesized by sonochemical co-precipitation method. The XRD pattern of the powders showed the characteristic peaks corresponding to the Ytype hexaferrite structure as a main phase and some CoFe2O4 impurity (< 2%) as a second phase. This result was also confirmed by Mössbauer spectroscopy measurements. The magnetization values at 50 kOe were 30 emu/g at 4.2 K and 26.6 emu/g at 300 K, respectively. The ZFC and FC magnetization curves were measured at magnetic fields of 50 Oe, 100 Oe and 500 Oe, which revealed a magnetic phase transition around 200 K from ferrimagnetic-to-helical spin order. This is considered as a precondition for the material to exhibit multiferroic properties.
Multiferroic properties and structural features of M-type Al-substituted barium hexaferrites
Physics of the Solid State, 2017
Precise studies of the crystal and magnetic structures of M-type substituted barium hexaferrites BaFe 12-x Al x O 19 (0.1 ≤ x ≤ 1.2) have been performed by powder neutron diffraction in the temperature range 300-730 K. The electric polarization and the magnetization, and also the magnetoelectric effect of the compositions under study have been studied in electric (to 110 kV/m) and magnetic (to 14 T) fields at room temperature. The spontaneous polarization and significant correlation between the dielectric and magnetic subsystems have been observed at room temperature. The magnetoelectric effect value is, on average, about 5%, and it increases slightly with the aluminum cation concentration. The precise structural studies made it possible to reveal the cause and the mechanism of formation of the spontaneous polarization in M-type substituted barium hexaferrites BaFe 12-x Al x O 19 (x ≤ 1.2) with a collinear ferromagnetic structure.
Study of the Properties of Co-Substituted Ba2Mg2Fe12O22 Hexaferrites
Proceedings of The 3rd International Electronic Conference on Materials Sciences, 2018
We present results from a study on the influence of the substitution of Mg 2+ cations in the Y-type Ba2Mg2Fe12O22 hexaferrite with magnetic cations, such as Co 2+ , on its structural and magnetic properties. The Ba2Mg0.4Co1.6Fe12O22 powder was synthesized by sonochemical co-precipitation method. The XRD pattern of the powders showed the characteristic peaks corresponding to the Ytype hexaferrite structure as a main phase and some CoFe2O4 impurity (< 2%) as a second phase. This result was also confirmed by Mössbauer spectroscopy measurements. The magnetization values at 50 kOe were 30 emu/g at 4.2 K and 26.6 emu/g at 300 K, respectively. The ZFC and FC magnetization curves were measured at magnetic fields of 50 Oe, 100 Oe and 500 Oe, which revealed a magnetic phase transition around 200 K from ferrimagnetic-to-helical spin order. This is considered as a precondition for the material to exhibit multiferroic properties.
Journal of Alloys and Compounds, 2014
Large single crystals of aluminum-substituted M-type barium hexaferrite BaFe 12-x Al x O 19 were obtained from carbonate flux. The Al content in the crystals can be controlled via the Al content of the flux up to x = 1.1 according to single crystal X-ray structure refinements. Al shows a distinct preference to substitute Fe on crystallographic sites with high coordination numbers by oxygen atoms, whereas no significant amounts of Al can be found on a tetrahedrally coordinated site. An increasing amount of the aluminum dopant results in a monotonous reduction of the Curie temperature from 440 to 415 °C and the saturation magnetization at room temperature from 68 to 57 emu/g for single crystal and from 61 to 53 emu/g for powder samples.
Mössbauer Analysis and Cation Distribution of Zn Substituted BaFe12O19 Hexaferrites
Journal of Superconductivity and Novel Magnetism
Barium hexaferrite is a well-known hard magnetic material. Doping using nonmagnetic cation such as Zn 2+ were found to enhance magnetization owing to preferential tetrahedral site (4f 1) occupancy of the zinc. However, the distribution of cations in hexaferrites depends on many factors such as the method of preparation, nature of the cation, and chemical composition. Here, Zn-doped barium hexaferrites (Ba 1−x Zn x Fe 12 O 19) were synthesized by sol-gel method. In this study, we summarized the magnetic properties of Ba 1−x Zn x Fe 12 O 19 (x = 0, 0.1, 0.2, 0.3) BaM, investigated by Mössbauer spectroscopy. Moreover, cation distribution was also calculated for all the products. Mössbauer parameters were determined from 57Fe Mössbauer spectroscopy and according to it, the A.
IOP Conference Series: Materials Science and Engineering, 2017
Aluminum-substituted barium hexaferrite (BaM) that have the general formula of BaFe 12-x Al x O 19 (x: 0, 1, 2, 3, 4, and 5) was obtained through the process of solid state reaction. The samples of Aluminum-substituted barium hexaferrite (BaM) were characterized using XRD to determine the phase structure, and by Raman Spectroscopy to know the chemical composition and structure. The single phase was obtained for the samples x = 0-4 from the weight percentage of the phase, and the other phase i.e. Al 2 O 3 and BaO have been achieved for the sample x = 5. The characterization of Raman spectrum on Aluminum-substituted barium hexaferrite (BaM) has been carried out using Bruker SENTERRA instrument. The presence of sharp peaks corresponded to A 1g mode shows the possibility of Al substitution in the barium hexaferrite system without any distortion in crystal symmetry. It is also observed that the substitution of A l in the BaFe 12 O 19 system leads to an increase in the intensity of resonance band when compared with the parent compound, which indicates a large polarizability variation during the vibrations in the Aluminum-substituted BaFe 12-x Al x O 19 compounds.
Study of Quasi-Monophase Y-Type Hexaferrite Ba2Mg2Fe12O22 Powder
Micro and Nanosystems, 2014
We present the structural and magnetic properties of a multiferroic Ba2Mg2Fe12O22 hexaferrite composite containing a small amount of MgFe2O4. The composite material was obtained by auto-combustion synthesis and, alternatively, by co-precipitation. The Ba2Mg2Fe12O22 particles obtained by co-precipitation have an almost perfect hexagonal shape in contrast with those prepared by auto-combustion. Two magnetic phase transitions, responsible for the composite's multiferroic properties, were observed, namely, at 183 K and 40 K for the material produced by auto-combustion, and at 196 K and 30 K for the sample prepared by co-precipitation. No magnetic phase transitions in these temperature ranges were observed for a MgFe2O4 sample, which shows that the magnesium ferrite does not affect the multiferroic properties of this type of multiferroic metarials.