Implementation of La3+ ion substituted M-type strontium hexaferrite powders for enhancement of magnetic properties

Journal Pre-proofs Implementation of La3+ ion substituted M- type strontium hexaferrite powders for enhancement of magnetic properties M.M. Hessien, Nader El-Bagoury, M.H.H. Mahmoud, Mohammed Alsawat, Abdullah K. Alanazi, M.M. Rashad PII: DOI: Reference:

S0304-8853(19)32935-X https://doi.org/10.1016/j.jmmm.2019.166187 MAGMA 166187

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Journal of Magnetism and Magnetic Materials

Received Date: Revised Date: Accepted Date:

21 August 2019 14 November 2019 20 November 2019

Please cite this article as: M.M. Hessien, N. El-Bagoury, M.H.H. Mahmoud, M. Alsawat, A.K. Alanazi, M.M. Rashad, Implementation of La3+ ion substituted M- type strontium hexaferrite powders for enhancement of magnetic properties, Journal of Magnetism and Magnetic Materials (2019), doi: https://doi.org/10.1016/j.jmmm. 2019.166187

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Implementation of La3+ ion substituted M- type strontium hexaferrite powders for enhancement of magnetic properties M. M. Hessien1,2, Nader El-Bagoury1,2, M. H. H. Mahmoud1,2, Mohammed Alsawat1, Abdullah K Alanazi1, M.M. Rashad2 1Advanced

Materials and Applied Metallurgy Group, Faculty of Science, Taif University, P.O. Box 888, Taif 21974, Kingdom of Saudi Arabia 2Central

Metallurgical Research and Development Institute (CMRDI), P.O. Box: 87Helwan, Cairo, Egypt

Abstract Lanthanum replaced strontium M-type ferrite particles, Sr1-xLa2x/3Fe12O19 (where x=0.0, 0.1, 0.2 and 0.3) have been elaborated using tartrate precursor pathway. The manipulation of different synthesis conditions was assayed. Typical, Sr2+ ion surplus and La3+ ion substitution was discovered to develop the phase evolution and the microstructure of M-type hexagonal ferrites. Indeed, appropriate strontium hexaferrite single phase of was acquired at annealing temperature ≥1100 °C for with Sr1.1Fe12O19, Sr1.0La0.067Fe12O19 and Sr0.9La0.133Fe12O19samples. A secondary α–Fe2O3 phase was recognized at all temperature for samples with composition Sr1.0Fe12O19, and Sr0.8La0.2Fe12O19. The crystalline aspects were strongly premised on the La3+ ion content as well as the annealing temperature. The morphology of M-type hexagonal ferriteclearly indicates that the synthesized powders existed as a closed pack plate-like. Thesaturation magnetization and the coercivity were found to gradually increase with annealing temperature and Sr2+ ion surplus. Interestingly, coercivity value was highly gained with incorporation of La3+ ion.A high coercive force (Hc =2366.5 Oe) was fulfilled by inserting La3+ ion of 0.1 into pure SrFe12O19 phase.

Keywords: Sr-M Hexaferrite; Precursor Synthesis; Tartrate; Substitution; Magnetic property;Annealing Temperature; Lattice Parameters. 1

1. Introduction M-type Hexagonal ferrites and their solid solutions has been a subject of continuous interest for several decades due to its excellent functional properties. Mtype hexaferrite are widely used on practice as permanent magnets, magnetic recording media, multiferroics and electromagnetic absorbing material [1-6]. Now a day, M-type strontium hexaferrite SrFe12O19 has outstanding magnetic and electrical properties

involving

high

saturation

magnetization,

large

magneto-

crystalline anisotropy, magnetic hysteresis loss, high dielectric constant, excellent chemical stability, high Curie temperature, high corrosion resistance and cost performance [7-10]. Accordingly, due to these magnificent features, strontium hexaferrite is utilized in different industrial and household applications. Such extensive fields are included magnetic recording media, permanent magnets, information data storage, microwave absorbers or radar absorbing materials (RAM), and magnetic fluids [11-13]. Consequently, the improvement of magnetic properties can be monitored by controlling the synthesis strategies as well as substitution of strontium or iron sites or both by different ions. Such replacement consequence is considerable adjustment in the magnetic features to fit the specific applications. However, subrogate of Sr2+ by La3+ ion in SrFe12O19 ferrite has been formerly fabricated utilized hydrothermal pathway. Moreover, the formed ferrite exhibits much higher magnetocrystalline anisotropy. Furthermore, the Lasubstituted samples display an analogous magnetization to that of SrFe12O19 [14]. Chen et al [15] synthesized Sr1−xLaxFe12O19 (x = 0.05, 0.1, 0.15, 0.2) through sol gel pathway to study the microwave absorption properties. Ghimire et al [16] investigate the impact of Cu2+ and La3+-Cu2+ inserting on the magnetic characteristics of Sr1−xLaxFe12−xCuxO19 (x = 0.0–0.5) hexaferrite (SrM) synthesized using a facile auto-combustion route followed by sintering. They find a marked amelioration in the saturation magnetization and the coercivity in La3+-Cu2+ replaced SrM. Hexaferrites Sr1−x La x Fe12O19 (x = 0, 0.15, 0.25, 0.5) have been elaborated by microwave-assisted sol-gel method [17]. The phase of α- Fe2O3 appeared at x = 2

0.25 and x = 0.5. The coercive force of La3+- substituted Sr-M ferrite is upgraded to 5960.2 Oe at x = 0.25. Ghanbari el al [18] tailored La/Ni-substituted strontium hexaferrite Sr0.8La0.2Ni x Fe12-x O19 using co-precipitation technique.

Moreover,

Feng and Tan [19] enhanced the magnetoelectric properties of SrFe12O19 by replacement of 0.3 Sr2+ with 0.2 La3+ ion to produce La0.2Sr0.7Fe12O19. Besides, Bhat and Want [20] are ascribed the impact of lanthanum and magnesium substituted strontium hexaferrites, having the composition Sr1−xLaxMgyFe12−yO19 (x, y = 0, 0.05, 0.10, 0.15, 0.20) prepared based on the citrate precursor strategy. La–Mg incorporated SrFe12O19 is augments the dielectric and the magnetic properties which could confirm higher memory storage efficiency. Herein, in the present study, pure SrFe12O19 as well as Sr1-xLa2x/3Fe12O19 where x=0.1, 0.2 and 0.3 are fabricated using a facile tartaric acid precursor route. Meanwhile, the impact of Fe/Sr molar ratio, annealing temperature and La3+ ion concentration on the phase evolution, crystallite size, microstructure and magnetic properties are examined.

2.

Experimental

2.1. Materials and procedure Iron (lll) chloride anhydrous FeCl3 (Sigma Aldrich), lanthanum (III) nitrate hexahydrate; La(NO3)3.6H2O(ACROS), strontium chloride hexahydrate; SrCl2.6H2O (RIEDEL-DE HAEN), and tartaric acid; C4H6O6 (RIEDEL-DE HAEN) used in the present study were utilized without any further purification. In order to prepare the crystalline La ion-substituted SrFe12O19 powders (Sr1-xLa2x/3Fe12O19 where x= 0.1, 0.2 and 0.3), tartaric acid acted as a chelating agent and as a fuel. As shown in Fig. 1, aqueous solutions of a pre-calculated amount of different Sr2+, Fe3+ and La3+ ions ratios based on inexpensive chloride salts were prepared. The different series were recorded in Table 1. Then, the tartaric acid was inserted to the various aqueous solutions. The total volume of the mixture was adjustedto 500 ml. The solutions were gently stirred at temperature 80oC to achieve a good homogeneity until dryness. Thereafter, the formed sticky gel was completely dried in the oven at 110°C overnight to evaporate the liquid content and to 3

produce the gelling mass precursors. Eventually, the formed precursors were annealed in a static atmosphere furnace up to the required annealing temperature from 1000 to 1200৹C for 2 hours.

2.2. Physical properties X-ray diffraction (XRD) profiles were distinguished by a model Bruker AXS diffractometer (D8-ADVANCE) with Cu Kα ((λ = 1.54056 A˚) radiation, operating at 40 kV and 10 mA to evaluate the phase evolution depending on the JointCommittee on Power Diffraction Standards (JCPDS) in the 2θ range from 10০to 80০. The average crystallite size (Dxrd) was estimated using the line broadening of the X-ray peaks applying the well-known Debye-Scherrer equation [21]: Dxrd= n /  Cos θ

(1)

where, θ is the Bragg angle, n is the Scherrer constant, and  is the full width at half maximum of the diffraction peak. The manipulation of Fe/Sr content as well as La3+ ion concentration and theheating temperature on the crystallo-aspects characteristics of hexagonal ferrite particles was recognized based on the following equation [15]: 1

4 h2 + 𝑘2 + 𝑙2

(

=3 𝑑2

𝑎2

)

𝑙2

+ 𝑐2

(2)

Where h, k, and l are Miller indices and d is interplanar distance. The unit cell volume (V) was defined with the values of a and c, [15] 𝑉=

3 2

𝑎2𝑐

(3)

Scanning electron microscopy (SEM) was used to demonstrate the surface morphology and the average particle size. Vibrating sample magnetometer (VSM, 7410-

4

LakeShore, USA) was used to study the changes in the magnetic properties. Magnetic features were implemented at room temperature in a maximum applied field of 20 kOe.

3. Results and Discussion 3. 1. Characterization of X-ray diffraction Fig. 2 evinces the phase evolution of strontium hexaferrite precursor elaborated using tartrate precursor strategy at Fe/Sr molar ratio 12/1 annealed at different temperatures from 1000 to 1200oC for 2h. Plainly, hexagonal SrFe12O19 (JCPDS # 801198) was recognized as a dominant phase. Diffraction peaks at 2θ values of 34.17o, 32.31o, 31.085, 30.34o, 37.15o, 63.16o and 56.8o corresponded to the strongest diffraction planes (114), (107), (0 0 8) (110), (203), (2200) and (2011) of hexagonal SrFe12O19 were distinguished. However, in all cases, a cubic α–Fe2O3 (JCPDS # 89-0599) was realized as a secondary phase. Diffraction planes (104), (110), (116), (024) and (012) at 2 θ values of 33.17o, 35.66o, 54.06o, 49.46o and 24.14o reflected the presence of α–Fe2O3 phase were emerged. Fig. 3 elicits the phase progression with Sr2+ ion surplus (Fe/Sr content was 12: 1.1) at various annealing temperatures. Clearly, fine crystalline M-type strontium hexaferrite was manifested by the disappearance of diffraction peaks linked to α–Fe2O3. Subsequently, the manipulation of La3+ ion on the crystal development of SrFe12O19 powders, samples with formula Sr1-xLa2x/3Fe12O19 where x=0.1, 0.2 and 0.3 were prepared at annealing temperatures 1000, 1100 and 1200 °C for 2h. Figs 4, 5 and 6 demonstrate the diffraction profiles of the Sr1-xLa2x/3Fe12O19 compositions at assorted temperatures 1000, 1100 and 1200oC, respectively. At low temperature 1000oC, the peaks imputed to α–Fe2O3 were predestined with M-type phase. Meanwhile, with La3+ ion concentration of Sr0.8La0.133Fe12O19 (x= 0.2) and Sr0.3La0.2Fe12O19 (x= 0.3), magnetite (Fe3O4 JCPDS No.:74-0748) was observed. At ≥ 1100 °C, a well-crystallized single M type hexaferrite phase was noticed. The absence of secondary phases indicates that the lanthanum ions were diffused completely into SrM crystal.

5

Debye–Scherrer equation was used to determine the crystallite size of the Sr1. xLa2x/3Fe12O19 phase

based on the main peak (107) in the XRD data. Evidently, it was

perceived that the crystallite size of Sr1-xLa2x/3Fe12O19 powders was found to increase with increment the annealing temperature from 1000 to 1200 °C for all La ion content as recorded in Table 2. The increasing of the crystallite size with raise the annealing temperature was corresponded to the grain development as well as the reduction of internal stress. Particularly, the crystallite size was also predicated on La ion concentration. The crystallite size at Sr0.9La0.067Fe12O19 (x= 0.1) was higher than at SrFe12O19 (without substitution) at all annealing temperature. Beyond x= 0.1, the crystallite size was decreased with increasing of La ion content. Indeed, it was found to decrease from 146.6nm for the sample Sr0.9La0.067Fe12O19 (x= 0.1) to 105.4 nm for sample Sr0.7La0.2Fe12O19 (x= 0.3) at annealing temperature 1000oC. The decreasing in the crystallite size with La ion content can be attributed to phase transition and the difference between ionic radii of La3+ and Sr2+ ions. These results indicate clearly that pure single phase SrFe12O19 has larger crystallite size than the substituted phase. Otherwise, Table 2 summarizes the distinction of the lattice constants, aspect ratio c/a and unit cell volume with raising the annealing temperature and La3+ ion concentration. For instance, the lattice constants a, c and unit cell volume were increased with increasing the annealing temperature for pure SrFe12O19 and Sr0.9La0.067Fe12O19 phases as the result of the formation of M-type hexaferrite and the ordered of the ions in the ferrite lattice. The unit cell volume (V) and the a and c parameters were found to be decreasing with increasing temperature of annealing by increasing the x value of the samples Sr0.8La0.133Fe12O19 and Sr0.7La0.2Fe12O19, respectively. The maximum contraction of the lattice parameters was observed after annealing the precursors at 1200 °C. Consequently, this evidences that the crystal structure becomes more compact with a high La substitution. The aspect ratio c/a was used to define the M-hexagonal structure type [21]. The M-type structure can be portended if the ratio is noticed in the range 3.917 and 3.963. As can be seen in Table 1, the aspect ratios of the produced samples (≈ 3.9126

3.920) were within the ratio range of M-type [22-24]. The change in lattice parameters can be attributed to the difference between ionic radii of La3+ (1.172 Å), Sr2+ (1.18 Å) and Fe3+ (0.64 A˚) ions as well as the interaction between rare earth and surrounding ions [25] whereas the overall change of the lattice parameters can be attributed to the average radius of the replaced ions. Equivalent amounts of La3+ ions were substituted for the Sr2+ ions have almost the same ionic radii but there was a possibility that a few of the La3+ ions (larger atomic radii) might have been substituted for the Fe3+ ions. Thus, a discrepancy between the enhancing and lowering in the lattice parameters was occurred, consequently causing irregular changes in a and c.

3.2. Microstructure The microstructure and the grain size distribution of investigated polycrystalline pure and La doped M-type strontium hexaferrites has been investigated by SEM and their images are shown in Figs. 7-8. Plainly, the pictures evince that the synthesized strontium hexaferrite powders possessed a closed pack plate-like hexagonal particles. This type of structure is good for the microwave absorbing devices and the photocatalytic and highly efficient adsorbents for most of the organic dye applications [26]. However, on surplus La3+ ion concentration in M-type hexaferrites, the size of grains became slightly larger and agglomerated. At high La3+ion content with various x values of 0.2 and 0.3, the large lamellar formations of plate-like structure with smaller crystals were exhibited in all samples as represented in Figs 7e-f and Figs 8a-f. Indeed, the micrographs for the sample with x = 0.2 (Figs 7e-f) revealed the topotactic formation of large hexagonal plates, with only a small fraction of smaller grains. The sample with x = 0.3 exhibited hexagonal crystals with different sizes ranging from hundreds nm to 3 μm and to smaller crystals, and irregular lamellar masses as presented in Fig.8. Moreover, the grain size of strontium hexaferrite was enhanced with the annealing temperature and the La3+ ion ratio. The SEM micrograph also demonstrates that the samples produced at the same conditions have different values of porosity and density. This was due to the change in grain size. The sample Sr0.9La0.067Fe12O19 (x=0.1) had minimal porosity while sample 7

Sr0.7La0.2Fe12O19 (x=0.3) had maximal porosity. It was concluded that the porosity and grain size increases with increasing substitution contents [27-28]. SEM micrograph shows that sample with x = 0.0 exhibited hexagonal crystals with average grain size around 5 μm. A slight decrease in the average grain size to around 3 μm for x=0.1. The average grain size of irregular plate-like structure grains increased with increasing x up to around 13 μm for x=0.3. Samples with larger grains (x=0.3) have high porosity due to the formation of large cavities between irregular plate-like grains [27-28]. Qualitative elemental analyses through energy-dispersive X-ray interpretation (EDX) were also performed on powder samples of Sr0.8La0.2Fe12O19 produced byannealing at 1100ºC to illustrate the behavior and the distribution of each element during the formation process. The EDX analysis maps for Fe, Sr, O and La elements are given in Fig. 9 while the EDX spot analysis of Sr0.8La0.2Fe12O19 annealed at 1100 ºC is manifested in Table 3. It can be recognized that Fe, Sr, O and La elements are distributed between the plate – like structure (hexaferrite) and the small crystals, with larger concentration of Fe and Sr in the plate – like structure phase. Sr was mostly presented in the plate – like structure while La was mostly presented in the small crystals and with little concentration in the plate – like structure. These results prove that the plate – like structure were formed from the aggregation of the small crystals that were observed around the single plate – like crystals.

3.3. Magnetic measurement Figs. 10-13 identify the compositional dependencies of magnetic hysteresis loops of pure and La substituted M-type hexaferrite samples measured by VSM. Table 4 summarizes the magnetic parameters such as saturation magnetization (Ms), remnant magnetization (Mr), squareness ratio Mr/Ms and intrinsic coercivity (Hc).The results revealed that the magnetic particular of hexagonal powders were found to evidence the high conditional upon the temperature and the lanthanum ion ratio. In all cases for pure 8

and substituted La3+ ion, the Ms and Hc were found to gradually increase and attain the utmost values at 1200°C. Maximum saturation magnetization (Ms= 62.8 emu/g) and maximum coercive force (2366.5 Oe) were gained at annealing temperature 1200oC for Sr0.9La0.067Fe12O19 sample. The La3+ substituted Sr2+ ion led to the change of Fe3+ to Fe2+ at 2a sites as the result of an enhancement of the Fe3+–O–Fe2+ super-exchange interaction in the hyperfine field at 12 k, 2b sites, consequently, saturation magnetization was increased. It is known that, M-type hexaferrite possesses five sublattices: three octahedral sites (2a, 12k and 4f2), one tetrahedral site (4f1), and one trigonal-bi-pyramidal site (2b) [7,8,17,19]. The magnetic moment of strontium hexaferrite originates from Fe3+ ions occupying the five various sublattices of hexaferrite. Fe3+ ions in the 4f1 and 4f2 sites have down spins, whereas these in the 2a, 2b and 12k sites have up spins. Hence, the net magnetic moment is the changes between the magnetic moments with up spin and down spin. Thereby, the mutation of Ms value related to the ion content concerns on the replacement of magnetic Fe3+ ions by nonmagnetic ions and the discriminatory site occupancy of nonmagnetic cations [14,15,25,29]. The net magnetization increases if the nonmagnetic La3+ ions is substituted with Fe3+ ions in the spin-down sites (4f1 and 4f2) [14,15,25,29]. Therefore, Ms increases at the La3+ concentration of x =0.2 in this study. If the nonmagnetic La3+ ions occupy the spin-up sites (2a, 2b and 12k) or the La3+ ions substituted by the Fe3+ ions in the spin-up sites, the net magnetic moment and/or magnetization decreases [14,15,25,29]. In this study, Ms thus decreases with increasing La3+ ion concentration (x=0.4 and 0.6). Interestingly, the Hc was highly increased with the influence of La3+ ion, especially with small substitution, at all studied annealing temperature. Hc was increased from 1100 Oe for the unsubstituted Sr1.1Fe12O19 to 2366.5 Oe for sample with x = 0.1 (Sr0.9La0.067Fe12O19). A gradual decrease in Hc was presented with increasing La3+ ion substitution x > 0.1 (Sr0.8La0.133Fe12O19 and Sr0.7La0.2Fe12O19) but still higher than that for un-substituted Sr1.1Fe12O19. In all cases, lanthanum substituted strontium hexaferrite had higher coercivity than un-substituted strontium hexaferrite. It can be concluded that the increase of coercivity in Sr0.9La0.067Fe12O19 is attributed to enhancement in magnetic crystalline 9

anisotropy field due to substitution of La [29]. Therefore, the best substitution level was to be x = 0.1 (Sr0.9La0.067Fe12O19) and annealing temperature 1200 °C to have the highest coercivity and high saturation magnetization. For application of hexagonal ferrite in the recording media, high coercivities are averted to ease re-recording for most recording media involved DC, DVD and video tape. However, for identification cards and credit cards, high coercivity is demanded to avoid the risk of data becoming deteriorated when the cards are exposed to aberrant magnetic fields [30]. Moreover, the coercivity with ≥ 100 Oe is acrucial conditions for EM materials for the defeat of electromagnetic interference (EMI) security, and microwave. On the other hand, the lower Ms and Hc arise at Fe/Sr molar ratio 12/1 (SrFe12O19, Table 4) were imputed to the formation of large amounts of intermediate α-Fe2O3, as XRD analysis, as well as the low crystallinty of SrFe12O19. The saturation magnetization Ms of the powders demonstrated a steady increase with the annealing temperature. The increase of Ms with the annealing temperature was imputed to the enhancing the crystallinity of M-type ferrite and the phase homogeneity with increment the temperature. For increasing Fe/Sr molar ratio 12/1.1, improvingthe saturation magnetization (Ms), the remanance magnetization (Mr) as well as the coercivity (Hc) was noticed which was lower than the obtained via co-precipitation route [29]. This improvement was linked to the increase of the phase evolution of strontium hexaferrite where a single phase was indexed at ≥1100°C as well as the growth of grain size [32-33]. The squareness ratio Mr/Ms is essentially a measure of squareness of the hysteresis loop. The results showed that sample with Fe/Sr molar ratio 12/1 (SrFe12O19) had very low value ≈ 0.1. This could be due to the increase in the fractions of the non-magnetic α– Fe2O3 phase and uncompleted formation of hexaferrite. For samples Sr1.1Fe12O19 and Sr1xLa2x/3Fe12O19

(x= 0.1, 0.2 and 0.3), the Mr/Ms increased with increasing annealing

temperature. Moreover, the Mr/Ms value increased with increasing La3+ ion substitution. Maximum Mr/Ms (≈ 0. 49) was observed at 1200°C for sample Sr0.7La0.2Fe12O19. It is

10

reported that if Mr/Ms ratio ≥ 0.5, then the hexaferrites are in single domain while if the squareness ratio is ≤ 0.5, then the hexaferrite are in multimagnetic domains [34].

4. Conclusions On brief, the results can be epitomized as follows -

Strontium hexaferrite compounds Sr1-xLa2x/3Fe12O19 (x= 0.1, 0.2 and 0.3) with and without La substitution have been synthesized by tartaric acid precursor method

-

The lattice parameters a and c are found to diminish with augment La3+ content due to the smaller ionic radius of La3+ ions compared with Sr2+ ions

-

The aspect ratio c/a was in the range 3.917 and 3.963 which approved M-hexagonal structure type

-

The nonmagnetic La3+ ions subrogate Sr2+ ions, which will restrain the superexchange interactions and weaken the magnetic ions interaction, subsequently, will enhance the magnetic crystalline anisotropy.

-

The synthesized strontium hexaferrite powders manifested a closed pack plate-like hexagonal particles

-

EDX spot analysis were distinguished that Fe, Sr, O and La elements were distributed between the plate – like structure (hexaferrite) and the small crystals, with larger concentration of Fe and Sr in the plate – like structure phase.

-

Surplus La3+ ion concentration in M-type hexaferrites was improved the saturation magnetization and the coercivity

-

Such produced powders are the good nominate in manifested purposes involving recording media, microwave absorbing devices and household applications

Acknowledgement 11

This study was funded by the Deanship of Scientific Research, Taif University, Saudi Arabia (research project number 6071 - 439 - 1).

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Table 1: Synthesis conditions of La substituted strontium hexaferrite powders Charge No 1

2

3

4

5

Conditions Charges in mol (M) 1.0 M SrCl2.6H2O + 12 M FeCl3 + 19 M C4H6O6

266.62 )g 𝑘

(

0.9 M SrCl2.6H2O + 0.133 M La(NO3)3.6H2O + 12 M FeCl3 + 19 M C4H6O6 0.8 M SrCl2.6H2O + 0.2 M La(NO3)3.6H2O + 12 M FeCl3 + 19 M C4H6O6

SrCl2.6H2O + ( 2851.65 ( 𝑘 )g

)g FeCl3 +

1946.52 𝑘

C4H6O6

293.282 )g SrCl2.6H2O + ( 𝑘 1946.52 2851.65 )g FeCl3 + ( 𝑘 )g 𝑘

SrFe12O19

(

1.1 M SrCl2.6H2O + 12 M FeCl3 + 19 M C4H6O6 1.0 M SrCl2.6H2O + 0.067 M La(NO3)3.6H2O + 12 M FeCl3 + 19 M C4H6O6

Target

Charges in gram (g)

Sr1.1Fe12O19

C4H6O6 266.62 )g 𝑘

(

28.87 )g 𝑘 1946.52 ( 𝑘 )g

SrCl2.6H2O + (

La(NO3)3.6H2O +

2851.65 )g 𝑘

FeCl3 + ( 239.96 )g 𝑘

(

57.74 )g 𝑘 1946.52 ( 𝑘 )g

2851.65 )g 𝑘

FeCl3 + ( 213.30 )g 𝑘

FeCl3 +

17

Sr0.8La0.133Fe12O19

C4H6O6

86.61 )g 𝑘 1946.52 ( 𝑘 )g

SrCl2.6H2O + (

La(NO3)3.6H2O +

k is an arbitrary scaling factor.

19

C4H6O6

SrCl2.6H2O + (

La(NO3)3.6H2O +

(

Sr0.9La0.067Fe12O

2851.65 ( 𝑘 )g

C4H6O6

Sr0.7La0.2Fe12O19

Table 2: Crystallite size, lattice parameters and unit cell volume on Sr1.1-xLa2x/3Fe12O19 crystalline powders at various temperatures from 1000 to 1200oC for 2h

Composition

Sr1.0Fe12O19

Sr1.1Fe12O19

Sr0.9La0.067Fe12O19

Sr0.8La0.133Fe12O19

Sr0.7La0.2Fe12O19

Temperature, (ºC)

Crystallite size, Dxrd, (nm)

a, (Å) ±4 x 10-4

c, (Å) ±4 x 10-4

c/a ±4 x 10-3

Unit cell volume, V, (Å3) ±4 x 10-3

1000

111

5.8725

22.9863

3.914

686.514

1100

134

5.8718

22.9954

3.918

686.627

1200

143

5.8628

22.9952

3.914

685.895

1000

123.8

5.8666

22.9638

3.914

684.459

1100

146.8

5.8733

22.9770

3.912

686.421

1200

162.6

5.8738

22.9784

3.912

686.762

1000

146.6

5.86536

22.96808

3.916

684.297

1100

173.9

5.87136

22.9841

3.913

686.176

1200

175.5

5.88484

23.03992

3.915

687.843

1000

133.0

5.87446

23.00576

3.916

687.548

1100

138.4

5.87158

23.00168

3.918

686.752

1200

159.6

5.869626

22.9975

3.918

686.1706

1000

105.4

5.87298

23.0024

3.917

687.1014

1100

131.5

5.87208

22.98944

3.915

686.504

1200

142.6

5.87082

22.98272

3.915

686.001

Lattice constant

18

Table 3: Spot Analysis Range of Constituent Elements in the Sr0.7La0.2Fe12O19Phase, wt-% Element,

Fe

O

Sr

La

Plate-Like

55.94 –

23.32 –

6.25 –

1.43 –

structure

66.15

34.26

8.35

1.90

small

68.72 –

27.1 –

0.79 –

2.39 –

crystals

78.15

35.03

2.53

5.21

All area

72.75-

15.42 –

4.42 –

3.99 - 5.21

(maps)

76.15

17.65

4.44

wt-%

19

Table 4: Effect of Fe3+/Sr2+ mole ratio, La3+ ion substitution and annealing temperature on the magnetic properties of strontium hexaferrite

Composition

Sr1.0Fe12O19

Sr1.1Fe12O19

Sr0.9La0.067Fe12O19

Sr0.8La0.133Fe12O19

Sr0.7La0.2Fe12O19

Magnetic Properties Temperature, (ºC)

Saturation magnetization Ms, (emu/g)

1000

45.01

4.30

275.1

0.100

1100

47.63

4.73

375.2

0.099

1200

51.11

4.92

420.4

0.096

1000

47.97

5.56

389.3

0.116

1100

55.87

15.80

916.9

0.208

1200

60.07

16.04

1100.0

0.267

1000

51.6

16.51

840.1

0.320

1100

57.6

24.06

1874.2

0.418

1200

62.8

27.53

2366.5

0.438

1000

51.9

21.61

1229.7

0.416

1100

54.7

24.25

1522

0.443

1200

53.6

24.65

1782.4

0.460

1000

42.5

7.56

372.7

0.178

1100

50

9.40

472.4

0.188

1200

47.1

23.29

1674.6

0.492

20

Retentivity Coercivity Mr/Ms Mr,(emu/g) Hc,(Oe)

Fig. 1: Flow-sheet diagram for synthesis Sr1-XLa2x/3Fe12O19 using tartrate precursor strategy

21

Fig. 2: XRD patterns for composition Sr1.0Fe12O19 (La=0.0) from strontium-iron tartrate precursor

Fig. 3: XRD patterns for composition Sr1.1Fe12O19 (La=0.0) from strontium -iron tartrate precursor

22

Fig. 4: XRD patterns for composition Sr1.0La0.067Fe12O19 from strontium – lanthanum -iron tartrate precursor

Fig. 5: XRD patterns for composition Sr0.9La0.133Fe12O19 from strontium – lanthanum -iron tartrate precursor

23

Fig. 6: XRD patterns for composition Sr0.8La0.2Fe12O19 from strontium – lanthanum -iron tartrate precursor

24

Fig. 7: SEM micrographs of Sr1-xLa2x/3Fe12O19 crystalline powders (x=0, 0.1and 0.2) at various temperatures; (a,b) x=0.0 & 1100oC, (c,b) x=0.1 & 1100oC, (e,f) x=0.2 & 1100oC

25

Fig. 8: SEM micrographs of Sr0.7La0.2Fe12O19 (x=0.3) crystalline powders at various temperatures; (a,b) 1000oC, (c,b) 1100oC, (e,f) 1200oC

26

Fig. 9: The SEM mappings of Sr0.8La0.2Fe12O19 obtained at 1100°C for the distribution of (a) real image, (b) strontium, (C) iron, (d) oxygen, (e) lanthanum and (F) the associated EDX spectra

27

Fig. 10: Effect of calcination temperature on the hysteresis loop of Sr1.0La0.067Fe12O19.

Fig. 11: Effect of calcination temperature on the hysteresis loop of Sr0.9La0.133Fe12O19 28

Fig. 12: Effect of calcination temperature on the hysteresis loop of Sr0.8La0.2Fe12O19

Fig. 13: Variation of Saturation magnetization (Ms) and Coecivity (Hc) as function of La3+ ion content and annealing temperature 29

Author statement

M. M. Hessien: Conceptualization, Methodology, Investigation, Supervision Nader El-Bagoury: Visualization, Investigation M. H. H. Mahmoud: Data curation, Writing- Original draft Mohammed Alsawat: Formal analysis, Software Abdullah K Alanazi: Methodology, Validation M. M. Rashad: Writing- Reviewing and Editing

Conflict of Interest and Authorship Conformation

Please check the following as appropriate:

o

All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version.

o

This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue.

30

o

The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript

Dr. Mahmoud Hessien

Highlights  Surplus Sr2+ and La3+ incorporated SrFe12O19 improves the magnetic features.  The crystallo-aspects characteristics decreases with La3+ content.  EDX analysis confirm Fe, Sr, O and La atoms distributed between the plate shape.  Nonmagnetic La3+ ions enhance the magnetic crystalline anisotropy.  Such compounds are a good choice for recording media and household applications.

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