Investigation on structural and magnetic properties of Al3+ and Ce3+ doped hexaferrites

Venkatesh, G.; Subramanian, Ramanathan; Kumar, T. Satish; Abuthakir, J.; Berchmans, L. John; Sethupathi, K.

doi:10.1016/j.matpr.2019.10.029

Cited by 8 publications

(3 citation statements)

References 25 publications

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“…However, the grain sizes calculated from the FESEM micrographs are much larger than the crystallite sizes. A similar case has been reported for bulk materials [26,27]. This may be due to the grains being formed by agglomerating multiple crystallites into single grain particles separated by grain boundaries.…”

Section: Structural Analysissupporting

confidence: 78%

Low-frequency electrical response related to oxygen vacancies in Al³⁺ substituted M-type hexaferrite

Singh

Mohapatra

Dobbidi

et al. 2023

J. Phys. D: Appl. Phys.

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The presence of oxygen vacancies is unavoidable in many metal complex oxide materials such as hexaferrite. So, this article investigates the role of crystal defects such as oxygen vacancies, and different oxidation states of Fe ions on electrical conduction behaviours of Al3+ substituted Ba0.4La0.1Sr0.5AlxFe12-xO19 hexaferrite by analyzing temperature dependents AC impedance, and AC conductivity. The optimal substitution of La3+ ions and high-temperature sintering is responsible for forming oxygen vacancies while reducing Fe into Fe3+ to Fe2+ cations, observed in structural and XPS analysis, which affects electrical conduction behaviours. The departure from ideal Debye-type relaxation behavior is also one of the effects of crystal defects. Temperature variation relaxation time observed a sharps change at around 403K. This may be due to different electrical entities influence the mode of electron hopping with the temperature. The activation energy calculated from the temperature dependents relaxation time confirmed the presence of the electron hopping through bridging effects of the first ionization of oxygen vacancies Fe2+-V^.o- Fe3+ below temperature 403K. Whereas, above 403K, electron hopping through different oxidation states of Fe2+ + e → Fe3+ and migration of oxygen vacancies toward the bulk surface are responsible for the conduction mechanism. The DC resistivity and AC conductivity briefs that the bridging effects of oxygen defects can also induce Coulombic interaction between the defects sites resulting in Efros-Shklovskii-Variable-Ranges hopping (ES-VRH) and Correlation-Barrier hopping (CBH) below temperature 403K. Above 403K, polaron-assisted electron hopping is more desirable, as confirmed by Non-Overlapping Small Polaron Tunnelling (NSPT)model.

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Section: Structural Analysissupporting

confidence: 78%

Low-frequency electrical response related to oxygen vacancies in Al³⁺ substituted M-type hexaferrite

Singh

Mohapatra

Dobbidi

et al. 2023

J. Phys. D: Appl. Phys.

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“…The calculation of grain size is performed using ImageJ software and observed that the average grain size decreased from 1.02 µm to 0.9 µm with increasing Al 3+ content and is found to be larger than the crystallite size. This behaviour is typical of bulk materials, where grain particles are formed by aggregating multiple crystallite particles [36].…”

Section: Structure and Microstructural Studiesmentioning

confidence: 87%

Exploring the role of oxygen vacancies on the magnetic and electromagnetic absorption properties of La³⁺-modified M-type hexaferrite with Al³⁺ doping

Singh,

Mohapatra,

Pal

et al. 2023

J. Phys.: Condens. Matter

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The demand for effective microwave-absorbing materials has recently surged due to rapid advancements in electromagnetic (EM) devices. Recently, engineering oxygen vacancies has also become one of the effective ways to develop efficient microwave-absorbing materials. So, understanding the EM absorption mechanism of these materials has become crucial for better engineering of such materials. This article investigates the magnetic properties along with the EM absorption mechanism of M-type hexaferrite, with optimal incorporation of rare-earth element La3+ and doping of transition metal Al3+ cation. The presence of La3+ ions at an optimal level promotes the reduction of Fe3+ to Fe2+ cations and creating oxygen vacancies to offset the electrical charge imbalance. This phenomenon impacts both the magnetic and EM characteristics of the materials. The presence of Fe2+ cations enhanced the spin-orbital interaction, resulting in a strong magnetic anisotropy field along the c-axis. The lowest reflection loss of −36.37 dB at 14.19 GHz, is observed with a bandwidth of 3.61 GHz below −10 dB for x = 0.6. These microwave absorption properties can be attributed to the adequate compensation between dielectric and magnetic losses, which arise from phenomena like dielectric relaxation, magnetic resonance, and conduction loss due to electron hopping between Fe3+ and Fe2+ with proper incorporation of the attenuating constant and excellent impedance matching, along with microstructure of the materials. Furthermore, the material’s exceptional absorption properties are also influenced by the rapid movement of oxygen vacancies from its interior to its surface when exposed to high frequencies, thereby impacting its conductivity. Therefore, it is believed that the regulation of oxygen vacancies can serve as a versatile strategy for developing materials with efficient microwave-absorbing capabilities.

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“…Nano-hexaferrites have been prepared using La-Nd, Mn-Y, Zr-Nd and Sm-Er co-dopants [13][14][15][16]. The co-doping for the magnetization enhancement of Sr-hexaferrites has been performed by Al-Ce, Nb-Y, Ce-Zn, Ce-Mn, La-Co and Dy-Al and in these studies sol-gel, coprecipitation and low temperature sintering methods have been carried out [17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Effect of Rare-Earth Co-Doping on the Microstructural and Magnetic Properties of BaFe₁₂O₁₉

Güler

Ertuǧ

Işıkcı

et al. 2020

Advances in Materials Science

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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.

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Investigation on structural and magnetic properties of Al3+ and Ce3+ doped hexaferrites

Cited by 8 publications

References 25 publications

Low-frequency electrical response related to oxygen vacancies in Al³⁺ substituted M-type hexaferrite

Low-frequency electrical response related to oxygen vacancies in Al³⁺ substituted M-type hexaferrite

Exploring the role of oxygen vacancies on the magnetic and electromagnetic absorption properties of La³⁺-modified M-type hexaferrite with Al³⁺ doping

Effect of Rare-Earth Co-Doping on the Microstructural and Magnetic Properties of BaFe₁₂O₁₉

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Investigation on structural and magnetic properties of Al3+ and Ce3+ doped hexaferrites

Cited by 8 publications

References 25 publications

Low-frequency electrical response related to oxygen vacancies in Al3+ substituted M-type hexaferrite

Low-frequency electrical response related to oxygen vacancies in Al3+ substituted M-type hexaferrite

Exploring the role of oxygen vacancies on the magnetic and electromagnetic absorption properties of La3+-modified M-type hexaferrite with Al3+ doping

Effect of Rare-Earth Co-Doping on the Microstructural and Magnetic Properties of BaFe12O19

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Low-frequency electrical response related to oxygen vacancies in Al³⁺ substituted M-type hexaferrite

Low-frequency electrical response related to oxygen vacancies in Al³⁺ substituted M-type hexaferrite

Exploring the role of oxygen vacancies on the magnetic and electromagnetic absorption properties of La³⁺-modified M-type hexaferrite with Al³⁺ doping

Effect of Rare-Earth Co-Doping on the Microstructural and Magnetic Properties of BaFe₁₂O₁₉