Synthesis and Characterization of Barium Hexagonal Ferrite (BaFe12O19)

Barium Ferrites is a good class of electrical material due to its high resistivity. It is mainly used in electronics and telecommunication industry due to their novel electrical properties. We have synthesized barium hexagonal ferrite (BaFe12O19) by solid state reaction method. The prepared precursor was calcined at temperature 750°C and characterized by FTIR, XRD and SEM. X-ray diffraction analysis confirmed the single-phase formation of BaFe12O19. Using the Debye Scherrer formula, the crystallite size of BaFe12O19 was calculated, and the average particle sizes were 26.52 nm, 27.17 nm, 19.17 nm and 23.67 nm. The result confirms that barium ferrite powder has a constant size of less than 30 nm. Four peaks at 2θ values of 35.52, 43.22, 57.21 and 62.84 degrees, corresponding to (110) (111) (210) and (211) planes of Barium ferrite have been observed. The FTIR spectra showed important signature absorption spectra of hexaferrite at 314 cm−1, 499 cm−1 & 628 cm−1. These peaks confirm the formation of barium hexaferrites. The SEM images of barium hexaferrite at 750°C showed large number of vertically grown barium hexaferrite nanorods with a grain size between 110 nm to 130 nm. Thus, barium ferrite is a good candidate in the use of electronics and communication sector.


Introduction
Barium ferrites (BaFe12O19), is an enduring magnet widely recognized for its magnetic importance in last few decades.BaFe12O19 is having magneto plumbite-type hexagonal structure crystal anisotropy along c-axis.Barium ferrite exhibits outstanding features like high saturation magnetization (72 emu/g), with good coercive force with minimum manufacture cost, high curie temperature (450 o C) with large chemical constancy and resistance to corrosion [1].They are alternatively mentioned as ferrite magnets and possess a different irreplaceability, finds wide-range application in magnetic recording media, computer data storage, fabrication of commercial permanent magnet, microwave devices, and electromagnetic shielding fields [2].
To obtain peak performance, it is critical to have enormously fine barium hexaferrite powder with a constantly maintained particle size distribution of approximately 0.1 micro meters, along with wellregulated magnetic properties.Hence it is required to make changes in the physical properties of component which sturdily dependent on the preparation technique.With this respect, several chemical processes carried out at low temperatures were explored to produce ultrafine BaFe12O19 Particles [3].
IOP Publishing doi:10.1088/1757-899X/1300/1/012012 2 Some of the previous methods executed for synthesis were co-precipitation, hydrothermal synthesis, sol-gel process, microemulsion method, citrate-precursor, glass crystallization, sonochemical activation, and mechanochemical activation.The key drawback of these methods is that, the size of the particle is inadequate and uniformly distributed for utilization such as recording media [4].
The present research aimed to investigate the influence of the Fe 3+ /Ba 2+ mole ratio and the inclusion of surfactants in the synthesis of nanocrystalline barium hexaferrite powder via the solid-state reaction technique.This investigation holds significance as it aids in understanding the strategies for regulating the synthesis of single-phase barium hexaferrite powder, characterized by a uniform ultrafine size, relatively at low calcination temperatures.This research work presents the findings for magnetic and structural characteristics of synthesized BaFe12O19 powder.

Sample preparation
The synthesis of Barium hexaferrite compounds followed the method described by (Asiri et al., 2018), via the conventional solid-state synthesis method, includes the mixing and combustion of high-purity reactants, viz.BaO (99.98% purity) and Fe2O3 (99.98% purity).[5].The sample mixture was thoroughly combined and finely ground using an agate mortar and pestle.The sample was further placed into an alumina crucible and subjected to 3 hours heating process at 750°C.The sample was cooled at room temperature and once again blended and ground before it was subjected to an additional 2-hours heating cycle at a temperature of 750°C inside the furnace.The experiment was repeated for final 1 hour heating at 750 o C [6].The procedure was completed to facilitate material blending and enhance the thermal transport mechanisms within the mixture.

Characterization
The X-ray Diffraction study was conducted for the synthesized sample of barium ferrite with goniometer (Ultima 3 theta-theta gonio, under 40kv/30mA-X-ray, 2/ -scanning mode, fixed monochromator) by referring the method of Vinnik et al., 2020.Data was compiled within the angular range extended from 10 to 80 degrees (2θ), with increase of 0.02 degree.In the initial stage of indexing the powder diffraction pattern, Miller indices (h k l) were assigned to each analysed peak.This indexing process was achieved using two different methods and datasets.To achieve this, it is required to determine a division constant, so that the values in the third column can be converted into numbers at this point the constant is 43 (135.694-93.053).(The Scherrer equation, used in X-ray diffraction and crystallography, serves as a mathematical tool to determine the size of sub-micrometer particles or crystallites within a solid.)The four peaks 2 values of 35.52, 43.22, 57.21 and 62.84 degrees.Corresponding to (110) (111) (210) (211) planes of Barium ferrite have been observed.To understand the morphology of the hexaferrite surface morphology was studied using SEM by the method describe by Mosleh et al., 2016.The SEM images of barium hexaferrites at 750 o C showed large number of vertically grown barium hexaferrites developed in the powder sample.Fourier transform infrared (FTIR) analysis was carried out using the method of Carol Trudel et al., 2019.The infrared spectra of all samples were captured using a Perkin Elmer (Model 783) IR spectrometer in a KBr medium at ambient room temperature.To investigate the ferrite phase formation the synthesized BaFe12O19 hexaferrite particles were characterized by Fourier transform infrared (FTIR) analysis.Infrared spectra of the calcinated samples were recorded at room temperature, layer the mid-IR range from 4000 cm -1 to 400 cm -1 .

SEM
The microphotographs of Barium hexaferrite powder are presented in Figure 2. The SEM images of barium hexaferrites at 750 o C showed large number of vertically grown barium hexaferrites developed in the powder sample.The grain size of the sample under investigation is observed and they are 116 nm, 127 nm.This indicates that the grain size ranges from 110 nm to 130 nm.

FTIR
The infrared spectra for all the samples were obtained using a Perkin Elmer (Model 783) IR spectrometer in a KBr medium at standard room temperature.To investigate the ferrite phase formation the synthesized BaFe12O19 hexaferrite particles were characterized by Fourier transform infrared (FTIR) analysis.The infrared spectra of the calcinated samples were attained at room temperature within the mid-IR of 4000 cm -1 to 400 cm -1 .Figure 3 shows FTIR spectra of BaFe12O19 hexaferrite particles calcinated at 750 o C for this.The absorption bands in the range of 350 cm -1 to 600 cm -1 are symbolic presence of hexaferrite.The peaks assign to magnetite, stretching vibration of FeO at tetrahedral and octahedral site confirms the synthesis of hexaferrite.Theoretical considerations suggests that there are three fundamental IR active modes to hexagonal structure [7].The three characteristics absorption bands around 314 cm -1 ,499 cm -1 and 628 cm -1 are due to oxygen vibrations in perpendicular to octahedral cation oxygen axis and spinal block as a whole [8].Typically, the vibration band specific to the spectral range from 430 cm -1 to 590 cm -1 shows the presence of hexagonal ferrite [9].The frequency bands falling within the 550-580 cm -1 range parallel to the vibrations of the bond between the oxygen ion and the tetrahedral metal ion (O-M tetra), while those in the 430-470 cm -1 range are associated with the bond between the oxygen ion and the octahedral metal ion (O-M octa) [10].The spectra showed a noticeable change in bond position, arising from alterations in the bond distance between Fe 3+ and O 2-ions in both tetrahedral and octahedral complexes.[11].

Conclusions
X-ray diffraction analysis affirms the presence of a singular BaFe12O19 phase.The Debye Scherrer formula was applied to determine the crystalline size of BaFe12O19, resulting in average particle sizes as 26.52 nm, 27.17 nm, 19.17 nm, and 23.67 nm.The result confirms that barium ferrite powder uniformed size less than 30 nm.The FTIR spectra show the important signature absorption points of hexaferrites at 314 cm -1 , 499 cm -1 & 628 cm -1 .These points confirm the formation of barium hexaferrites.The SEM images of barium hexaferrite at 750 o C showed large number of vertically grown barium hexaferrite nanorods.The grain size of the sample is lies between 110 nm to 130 nm.