Synthesis of Strontitum Hexaferrites Nanoparticals

ABSTRACT
The SrFe12O19 is hard magnetic material (hexa-ferrite) with magneto plum bite structure . It has attract much attention in past few decades due to their Scientific & Technological applications & in the frequency rages of microwave to radio frequency. Due to used for high frequency application in multilayer chip inductor. This is due to high magneto crystalline anisotropy , High curie temperature, High Electrical resistivity & High Di-electric constant as well as high saturation ( Magnetization & Coericivity).
The Dielectric & Magnetic properties of hexa-ferrites materials in the nano regime are significantly different from their bulk materials.
The work in this thesis consists of three aspects,

Synthesis of strontitum hexaferrites nanoparticals by Non-convetional Citrate precursor method (chemical method).
Effect of Annealing Temperature on Magnetic properties of strontitum hexaferrites.
Effect of Structural , Electrical & optical properties have been studied.

These samples were characterized through X-Ray diffraction for its size & properties. The particle size was determined in scherrer’s formula. The samples were studied for their full report showing their magnetic properties based on the hysteresis loop formation for the samples prepared at the two temperatures through VSM . Electrical & optical properties have been examined through Impedance analyzer & Photo Luminance.
2. Literature Review
Since the Discovery of the M type hexagonal ferrites in 1950’s . It has being of great Interest due to its application as permanent magnetic materials & perpendicular Recording media. Due to its low cost, the main reason for its great success at moderate magnetic properties. Various works has been carried to develop hexa-ferrite by various methods and their properties has been investigated. On other hand extensive work has been done to understand the effect of various dopant. It is found the doping of metal ion, rare earth ion substantially effects their properties. Work carried out in past few years on different processing methods and different dopants are given below:
Structural and magnetic properties of La3+substituted strontium hexaferrite nanoparticles prepared by citrate precursor method [16]
Ankush Thakur,R.R. Singh, P.B. Barman , Lanthanum (La3+) doped The effects of La3+on magnetic properties have been analyzed using vibrating sample magnetometer and discussed. The results show that the coercivity has been improved by substitution of La3+on iron sites; coercivity value found to be increased with increase in La3+ . La 3+doped strontium ferrite, prepared by citrate precursor technique, have been analyzed by means of X-ray diffraction (XRD), FESEM,FTIR and inductance capacitance resistance meter bridge. The XRD analysis shows that crystalline ferrite phase with hexagonal structure. when the precursor calcined at 900°C for 5h. The crystallite size is found in the range of 31–38nm and the elemental composition has been examined by energy dispersive X-ray. The dc electrical resistivity has been found to be increased with increasing La3+content.

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Synthesis of strontium hexaferrite nanoparticles prepared using co-precipitation method and microemulsion processing [17]
ADrmota,A.Žnidaršič andAKošak : , Strontium hexaferrite (SrFe12O19) nanoparticles have been prepared with co-precipitation in aqueous solutions and precipitation in microemulsion system water/SDS/n-butanol/cyclohexane, calcined in a wide temperature range, from 350 °C to 1000 °C in a static air atmosphere. The influence of the Sr2+/Fe3+molar ratio and the calcination temperature to the chemistry of the product formation, its crystallite size, morphology and magnetic properties were investigated. It was found that the formation of single phase SrFe12O19with relatively high specific magnetization (54 Am2/kg) was achieved at the Sr2+/Fe3+molar ration of 6.4 and calcination at 800 °C for 3h with heating/cooling rate 5 °C/min.The specific magnetization (DSM-10, magneto-susceptometer) of the samples was measured.
Preparation and investigation of magnetic properties of MnNiTi-substituted strontium hexaferrite nanoparticles[18]
M. Mozaffari, A. Arab,M.H. Yousefi, J. Amighian
M-type strontium hexaferrite powders with substitution of Mn2+, Ni2+and Ti4+ions for Fe3+ions has been prepared via the conventional ceramic method. In order to get nanoparticles, the obtained powders were milled in a high energy SPEX mill for 1h. XRD investigations of the unmilled and milled powders show that the prepared samples are all single phase hexaferrite. Lattice parameters and mean crystallite sizes of the powders were determined from the XRD data and Scherrer’s formula. TEM was used to analyze their structures, magnetizations and coercivities of the samples in a magnetic field of 15kOe have been determined from the hysteresis loops. It was found that magnetizations of the milled samples were smaller than the magnetization of the unmilled samples.
Synthesis, magnetic and dielectric properties of Er–Ni doped Sr-hexaferrite nanomaterials for applications in High density recording media and microwave devices [19]
Muhammad Naeem Ashiqa,,Muhammad Javed Iqbalb, Muhammad Najam-ul-Haqa,Pablo Hernandez Gomezc,Ashfaq Mahmood Qureshia
A sol–gel combustion method has been successfully employed for the synthesis of Sr-hexaferrite nanomaterials doped with Er3+and Ni2+at strontium and iron sites, respectively. A Simple and economic method has been used for synthesis of materials. The main aim for substitution of Er–Ni in Sr-hexaferrite is to improve magnetic properties and to reduce the crystallite size. We are able to improve the saturation magnetization and remanence with the doping of Er–Ni. Crystallite size is in the range 16–14nm, which is much smaller than that reported earlier. Dielectric constant is reduced which makes the material suitable for microwave devices.
Crystallization kinetics of strontium hexaferrite: Correlation to structural, morphological, dielectric and magnetic properties [20]
Ankush Thakur,R. R. Singh,P. B. Barman
Citrate precursor technique has been used to synthesize strontium hexaferrite and reported here. The crystallization process for ferrite phase formation has been investigated by TG/DTG/DTA for three different heating rates in air atmosphere. The thermal process mainly consists of three essential steps; first removal of water residues; second decomposition of organic compound and the third step is crystallization of SrF12O19. The activation energy of reaction is, 157 KJ/mole, evaluated using non-isothermal kinetic model. The precursor and crystallized SrF12O19samples have been characterized for structural, chemical, morphological, dielectric and magnetic properties Using XRD, FTIR, FESEM,LCR meter bridge and VSM respectively.
Influence of annealing temperature and doping rate on the magnetic properties of Zr–Mn substituted Sr-hexaferrite nanoparticles [21]
Muhammad Javed Iqbala,Muhammad Naeem Ashiqb,Pablo Hernández-Gómezc,José María Muñoz Muñozc,Carlos Torres Cabrerac
A series of M-type strontium hexaferrite samples having nominal composition SrZrxMnxFe12−2xO19(wherex=0.0–0.8) has been synthesized by the co-precipitation method. All the samples synthesized were of single magnetoplumbite phase. The particle size was found to be in the 40–65nm range for the samples annealed at 1193K while the samples annealed at 1443K were in the 100–200nm range. The saturation magnetization increase with temperature and reached maxima for the samples annealed at 1393K and then start to decrease while the coercivity decreases regularly with temperature.
Structural evolution and magnetic properties of SrFe12O19nanofibers by electrospinning [22]
Xiangqian Shen,Mingquan Liu,Fuzhan Song,Xianfeng Meng
The SrFe12O19/poly (vinyl pyrrolidone) (PVP) composite fiber precursors were prepared by the sol-gel assisted electrospinning with ferric nitrate, strontium nitrate and PVP as starting reagents. M-type strontium ferrite (SrFe12O19) nanofibers were derived from calcination of these precursors at 750–1,000°C.The composite precursors and strontium ferrite nanofibers were characterized by FTIR , XRD, SEM & VSM .After calcined at 750°C for 2h the single M-type strontium ferrite phase is formed by reactions of iron oxide and strontium oxide produced during the precursor decomposition process. The nano fiber morphology, diameter, crystallite size and grain morphology are mainly influenced by the calcination temperature and holding time. The SrFe12O19nano fibers characterized with diameters of around 100nm and a necklace-like structure obtained at 900°C for 2h, which is fabricated by nano sized particles about 60nm with the plate-like morphology elongated in the preferred direction perpendicular to thec-axis, show the optimized magnetic property with saturation magnetization 59Am2kg−1and coercivity 521kAm−1. It is found that the single domain critical size for these M-type strontium ferrite nanofibers is around 60nm.
Structural, dielectric and magnetic properties of Cr–Zn doped strontium hexa-ferrites for high frequency applications [23]
G. Asghar, M. Anis-ur-Rehman
M-type strontium hexa-ferrite nano particles with composition SrFe12−2xCrxZnxO19(X=0.0, 0.2, 0.4, 0.6, 0.8) were prepared by co-precipitation method and are reported for the first time. X-ray diffraction analysis confirmed the successful substitution of Cr and Zn ions in the strontium hexa-ferrite lattice. Structural morphology studied by SEM revealed that Cr–Zn doping inhabits the grain growth. Dielectric measurements were taken as a function of frequency in the range (10kHz to 3MHz). Both dielectric constants and dielectric losses were found to be decreasing with the increase in Cr–Zn concentration. As Cr–Zn doping favored the decrease in dielectric losses to a large extent (0.32–0.02) so the strontium hexa-ferrite with these dopants is very useful for high frequency applications.
Influence of the iron content on the formation process of substituted Co–Nd strontium hexaferrite prepared by the citrate precursor method [24]

Strontium hexa ferrite samples of different composition were prepared by the self-combustion method and heat-treated in air at 1100°C for 2h: SrFe12O19(S0), Sr0.7Nd0.3Fe11.7Co0.3O19(SS), Sr0.7Nd0.3Fe10.7Co0.3O19(SM) and Sr0.7Nd0.3Fe8.4Co0.3O19(SL). The phase identification of the powders was performed using XRD. Only sample SL (with the lowest iron concentration) shows well-defined peaks of the hexaferrite phase with no secondary phases. Nd–Co substitution modifies saturation magnetization (MS) and coercivity (Hc) but only samples with low Fe3+content (SL and SM) show the best magnetic properties, indicating that the best results for applications of this ferrite will be obtained with an iron deficiency in the stoichiometric formulation.
Sol–gel hydrothermal synthesis of strontium hexaferrite nanoparticles and the relation between their crystal structure and high coercivity properties [25]
Thi Minh Hue Dang1, Viet Dung Trinh1, Doan Huan Bui1, Manh Huong Phan2and Dang Chinh Huynh1
Hard magnetic strontium hexaferrite SrFe12O19nanoparticles were synthesized by the sol–gel hydrothermal method. The factors affecting the synthesized process, such as the mole proportion of the reactants, pH, temperature, the hydrothermal conditions and the calcination process, have been investigated. The crystal structures of these materials were refined by Rietveld method. The obtained materials have single crystal phase, equal nano-size, plate shape and high anisotropy. The high magnetic coercivity of 6.3 kOe with the magnetization at 11.1 kOe of 66 emu g−1at room temperature was observed for the strontium hexaferrite nanoparticles. For other nanoparticles (SrLnxFe12-xO19and SrFe12O19/CoFe2O4) synthesized on the basis of SrFe12O19the complex completion of the crystal structure distortion and the interaction between magnetic phases were observed.
Low-Temperature Hydrothermal Synthesis of Ultrafine Strontium Hexaferrite Nanoparticles [26]
Darinka Primc1,Miha Drofenik1,2and Darko Makovec1
Ultrafine strontium hexaferrite (SrFe12O19) nanoparticles have been synthesized by the hydrothermal treatment of an appropriate suspension of Sr and Fe hydroxides in the presence of a large excess of OH–at temperatures between 130 and 170 °C. To avoid the parallel formation of any undesired hematite (α-Fe2O3) during the synthesis, a large excess of Sr in the starting composition (Fe/Sr = 3) had to be used. When the treatment was performed below 170 °C, ultrafine nanoparticles were formed. The TEM images show they have a disc-like shape, approximately 12 nm wide, but only around 4 nm thick. The EDS analysis showed their composition corresponded to SrFe12O19. When the temperature of the hydrothermal treatment exceeded 170 °C, larger hexagonal platelet crystals appeared as a consequence of Ostwald ripening. The evolution of the size and morphology of the nanoparticles with the temperature of the hydrothermal treatment was also monitored by XRD and measurement of the magnetic properties.
A Simple Method for Synthesis of Strontium Ferrite Nanoparticles and their Polymeric Nanocomposites [27]
G. Nabiyounia*, A. Yousofnejada, M. Seraja, S. Farshad Akhtarianfarb ,D. Ghanbarib
Hard magnetic SrFe12O19(SrM) nanoparticles were synthesized by a facile sonochemical reaction. The magnetic nanoparticles were then added to acrylonitrile-butadiene-styrene, polystyrene, polycarbonate,and poly sulfone to make magnetic nanocomposites. The magnetic properties of the samples were also investigated using an alternating gradient force magnetometer. The strontium ferrite nanoparticles exhibited ferrimagnetic behaviour at room temperature, with a saturation magnetization of 39 emu/g and a coercivity of 5070 Oe.The distribution of the SrFe12O19nanoparticles into the polymeric matrixes increases the coercivity.
Magnetic, physical and electrical properties of Zr–Ni-substituted co-precipitated strontium hexaferrite nanoparticles [28]
Muhammad Javed Iqbala ,Muhammad Naeem Ashiqa,Pablo Hernandez-Gomezb, Jose Maria Munozb
A series of Zr–Ni-substituted strontium hexaferrite materials, SrZrxNixFe12−2xO19(x=0.0–0.8), was synthesized by the co-precipitation method and the crystallite size determined to be in the range of 30–47nm. The saturation magnetization increased from 72 to 98kAm−1while coercivity decreased from 1710 to 428Oe with Zr–Ni substitution. This improvement in both these properties makes these materials suitable for applications in recording media. The increase in resistivity suggests that the synthesized materials can be useful for application in microwave devices.
Structural and electromagnetic characteristics of substituted strontium hexaferrite nanoparticles [29]
Ali Ghasemia,,Akimitsu Morisakob
Substituted strontium ferrite SrFe9(Mn0.5Co0.5Zr)3/2O19has been prepared from sol–gel method. X-ray diffraction (XRD), transmission electron microscope (TEM) and vector network analyzer, were used to analyze the structure and dynamic magnetic properties. Powders of sample show a hexagonal fine platelet structure and narrow particle size distribution. Based on microwave measurement on reflectivity, SrFe9(Mn0.5Co0.5Zr)3/2O19may be a good candidate for electromagnetic compatibility and other practical applications at high frequency.