EVOLUTION OF FERRO ELECTRIC AND FERRO MAGNETIC PROPERTIES OF RARE EARTH ALUMINIUM SUBSTITUTED M-TYPE BARIUM HEXA FERRITES AT ROOM TEMPERATURE
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-09-01 |
| Journal | Digest Journal of Nanomaterials and Biostructures |
| Authors | F. SEHAR, S. ANJUM, Zeeshan Mustafa |
| Institutions | Lahore Garrison University, Lahore College for Women University |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study investigates the synthesis and characterization of rare earth aluminum-substituted M-type Barium Hexaferrites (BaAlxFe(12-x)O19, where x=0.2 to 1.2) to evaluate their potential as room-temperature multiferroics.
- Core Value Proposition: Successful synthesis of M-type Barium Hexaferrites exhibiting clear ferroelectric hysteresis loops and strong magnetic properties simultaneously at room temperature.
- Synthesis Method: The materials were prepared using the cost-effective and scalable powder metallurgy (solid-state ceramic) route.
- Structural Confirmation: XRD confirmed the formation of a pure M-type hexagonal phase, with lattice constants (âaâ and âcâ) decreasing as aluminum concentration increases due to the smaller ionic radius of Al3+ compared to Fe3+.
- Magnetic Performance: Increasing Al content results in a trade-off: Saturation Magnetization (Ms) decreases significantly (from 72.55 to 33.25 emu/g), while Coercivity (Hc) increases (from 2032 to 2375 Oe).
- Ferroelectric Mechanism: Electric polarization is induced by the shifting of iron ions within the oxygen octahedron (FeO6) structure under an applied electric field.
- Optical Properties: The indirect optical band gap (Eg) increases substantially (from 3.44 eV to 4.22 eV) as the crystallite size decreases with higher Al substitution.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value (x=0.2) | Value (x=1.2) | Unit | Context |
|---|---|---|---|---|
| Synthesis Temperature | 1100 | 1100 | °C | Calcination/Sintering for 2 hours |
| Crystal Structure | M-Type Hexagonal | M-Type Hexagonal | N/A | Space group P63/mmc |
| Lattice Constant âaâ | 5.89 | 5.72 | A | Decreases with Al substitution |
| Lattice Constant âcâ | 23.33 | 23.14 | A | Decreases with Al substitution |
| Crystallite Size Dp (114 peak) | 60.26 | 51.80 | nm | Decreases with increasing Al content |
| Saturation Magnetization (Ms) | 72.55 | 33.25 | emu/g | Decreases due to diamagnetic Al3+ substitution |
| Coercivity (Hc) | 2032 | 2375 | Oe | Increases due to lattice shrinkage |
| Indirect Optical Band Gap (Eg) | 3.44 | 4.22 | eV | Increases as crystallite size decreases |
| Max Remanent Polarization (Pr) | 22.5 | N/A | ”C/cm2 | Measured for x=0.2 sample |
| Coercive Electric Field (Ec) | 14.9 | N/A | KV/m | Measured for x=0.2 sample |
| Fe3+ Ionic Radius | 0.64 | 0.64 | A | Host ion radius |
| Al3+ Ionic Radius | 0.567 | 0.567 | A | Substituting ion radius |
Key Methodologies
Section titled âKey MethodologiesâThe M-type Barium Hexaferrites were prepared using the powder metallurgy (solid-state ceramic) route, followed by comprehensive characterization:
- Precursor Preparation: High purity oxides (Fe2O3, BaCO3, Al2O3) were mixed in stoichiometric proportions and wet-mixed in acetone for homogenization.
- Heat Treatment: The mixed samples were subjected to calcination/sintering at 1100 °C for 2 hours, followed by slow cooling to prevent quenching.
- Processing Steps: The material underwent grinding, green compact formation, sintering, regrinding (for homogeneity), and final machining.
- Structural Analysis (XRD): X-Ray Diffractometer (Bruker D-1 discover) was used to confirm the M-type hexagonal structure and calculate lattice constants and crystallite size.
- Elemental and Functional Analysis (EDS/FTIR): Energy Dispersive Spectroscopy (EDS) confirmed elemental composition (Fe, Ba, O, Al). Fourier Transform Infrared Spectroscopy (FTIR) confirmed the characteristic metal-oxygen vibrations (436 cm-1 and 611 cm-1) indicative of M-type hexaferrite formation.
- Morphological Analysis (SEM): Scanning Electron Microscopy was used to observe the typical platelet-like morphology and track grain size reduction with increasing Al content.
- Magnetic Characterization (VSM): Vibrating Sample Magnetometer (3 Tesla) measured the M-H loops to determine saturation magnetization (Ms) and coercivity (Hc).
- Optical Characterization (UV-VIS): UV-Visible spectroscopy (300-900 nm) was used in conjunction with the Tauc relationship to calculate the indirect optical band gap (Eg).
- Ferroelectric Characterization (ZT-IA): A ZT-IA measurement system was used to obtain Polarization-Electric field (P-E) hysteresis loops at room temperature, confirming ferroelectric behavior.
Commercial Applications
Section titled âCommercial ApplicationsâThe synthesized Al-substituted M-type Barium Hexaferrites are promising candidates for advanced electronic and magnetic engineering applications, particularly those requiring coupled magneto-electric functionality:
- Multiferroic Devices: Development of novel magneto-electric sensors, transducers, and memory elements that utilize the coupling between magnetic and electric order parameters at room temperature.
- Spintronics: Application in next-generation spintronic devices, where the ability to control magnetic state via an electric field (and vice versa) is critical for low-power operation.
- High-Density Magnetic Storage: The high coercivity (Hc) achieved with Al substitution makes these materials suitable for high-stability, high-density magnetic recording media.
- Permanent Magnets: Utilization as hard magnetic materials, especially where tailored coercivity is required for specific device geometries.
- Microwave Components: Use in high-frequency applications such as microwave circulators, isolators, and phase shifters due to their specific magnetic properties.
- Advanced Ceramics: The improved microstructural properties resulting from Al substitution are beneficial for manufacturing high-performance ceramic components.
View Original Abstract
The ferro-electric and ferro-magnetic properties of rare earth aluminium substituted Mtype barium hexa-ferrites with the composition of BaAlxFe(12-x)O19 where (x=0.2, 0.4, 0.6, 0.8, 1.0 and 1.2) have been prepared by oxides as precursors employing powder metallurgy route. The structural properties, functional groups, 3-D visualization, elemental analysis, surface morphology, magnetic, optical properties and ferro electric properties of the prepared samples have been characterized through X-Ray Diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FTIR), diamond visualization software, Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM), UV-Visible spectroscopy (UV-VIS) and ZT-IA measurement system respectively. The structural measurements depict the confirmation of M-type barium hexa-ferrite structure. EDS spectrum illustrate the elemental composition of the prepared materials for every corresponding âxâ values. The surface morphology shows the existence of platelet like intergranular pores. Magnetic measurements shows that the saturation magnetization (Ms) decreases and coercivity (Hc) increases with increasing aluminium contents. The optical band gap energy increases as the crystallite size decreases. The variation of electric polarization has also been occurred due to the shifting of iron ions in the unit cell structure of oxygen octahedron FeO6.