Morphology and Magnetic Properties of Hexagonal Ferrite Sr₁₋ₓMₓFe₁₂₋ₓZnxO₁₉ (M= La, Dy, Nd, Yb)

A permanent magnet in the form of a ring or disc is one of the components in many devices. In this project, hard magnetic ferrite with formula Sr₁₋ₓMₓFe₁₂₋ₓZnxO₁₉ (x= 0.1, 0.3, 0.5, 0.7, 0.9) (M= La, Nd, Dy, Vb) is used because of the low cost, high energy, good electrical insulation, hard to demagnetize and easy to process. Substitutions from Lanthanide group and zinc oxide (non magnetic material) are used in order to get different microstructures according to the value of hysteresis properties. Hysteresis parameters are investigated such as the remanence, Br, energy product (BH)max and coercive force He Conventional sintering technique is used with sample being formed in disc shape. From XRD result, it was found that the substitution of Yb₂O₃,Nd₂O₃,La₂O₃,Dy₂O₃ and ZnO to the strontium ferrite magnet stabilizes the magnetoplumbite phase. The results for density, Curie temperature and grain size are better than non-substituted Sr-M. As a conclusion, improvement of the magnetic properties has been done to produce high performance of Sr-M in the future

Structural, phase development and magnetic behavior of polycrystalline yttrium iron garnet

The interest of this work is to investigate the influence of sintering temperatures on the structural, phase development and the magnetic properties of polycrystalline yttrium iron garnet (Y3Fe5O12, YIG). The samples were prepared using α-Fe2O3 and Y2O3 as starting powders by employing a high-energy ball milling (HEBM) technique using a SPEX8000D mill and milled for 9 h. The samples were sintered for 9 h from 500 °C to 1400 °C with increments of 100 °C. Particle size analysis was carried out using a Transmission electron microscope (TEM). The phase development and crystallography study were determined using X-ray Diffractometer (XRD). Field emission scanning electron microscope (FeSEM) was used to study the morphology and microstructural evolutions of YIG. Parallel evolution on magnetic permeability components and Curie temperature were characterized by impedance analyzer. Magnetization-hysteresis (M-H) curve parameters were obtained from a vibrating sample magnetometer (VSM). The change in particle size from nano to micro was also studied with respect to sintering temperatures, structural, phase development and magnetic properties

Study the iron environments of the steel waste product and its possible potential applications in ferrites

In this project, the permanent magnets ferrites have been prepared by recycle the steel waste product. Steel waste is an impure material that contains the iron oxides and impurities. The steel waste product is a form of flakes is grinding for several hours to form a fine powder. The iron oxides powders are separated from magnetic and non-magnetic particle using magnetic particle separation. The magnetic particles was again been purified by using the Curie temperature separation. The magnetic powder carried out from the purification was heated at 500 o C for 6 hours at 6 o C/ mins to form hematite, Fe 2 O 3. The constitute amount of BaCO 3 and Fe 2 O 3 derived by steel waste product are mixed by using mechanical alloying to prepare the barium hexaferrites (BaFe 12 O 19). The samples were sintered at different temperature 600/800/1000/1200 o C for 6 hours at 6 o C/ mins. The composition of FeO, Fe 3 O 4 and Fe 2 O 3 of the steel waste product was carried out using X-ray Fluorescence (XRF) and Energy Dispersive Spectroscopy (EDAX). The crystallography of sample is observed by using X-ray Diffraction (XRD). Microstructure of samples was carried out by using Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscopy (AFM). The saturation magnetization, Curie temperature and density are also observed. The results show the purification process yields high purity of hematite, Fe 2 O 3. The common characteristics of the steel waste product are its low cost, availability and thus the potential for large production volumes, need for recycling, and tendency to further oxidation in the production of ferrites

Thermal and frequency stability of dielectric ceramic Ba6-3xNd8+2xTi18O54 (x=0.15, 0.25)

A new dielectric material, barium neodymium titanate (BNT) ceramic can provide good thermal and frequency stability on the dielectric properties. The synthesis of BNT ceramics with x=0.15 and 0.25 was carried out using wet solid state method. The ceramics were characterized by X-ray diffraction to identify the phase. The shifting of XRD peaks revealed higher content of neodymium ions inside the compound. Surface morphology of the ceramics was determined using FESEM. Different compositions influenced the grain growth of the ceramics. BNT ceramics with higher neodymium content showed higher porosity, and higher resistance to shrinkage. The dielectric properties at low frequency from 40 Hz to 1 MHz were measured using Impedance Analyzer. The polarization effect inside the material was discussed and compared. BNT ceramics with x=0.15 has higher dielectric constant. These BNT ceramics showed frequency and thermal stability with respect to the dielectric constant

Preparation and characterization of Sr1−xNdxFe12O19 derived from steel-waste product via mechanical alloying

Steel waste product had been used as the main source of raw material in the preparation of permanent magnets ferrites. Steel waste product is an impure material that contains the iron oxide and impurities. The steel waste product is a form of flakes is grinding for several hours to form a fine powder. The iron oxide powder is separated from magnetic and non-magnetic particle using magnetic particle separation. The magnetic particle was again been purified by using the Curie temperature separation technique. The magnetic powder was carried out from the purification and oxidize at 500 °C for 6 hours at 2 °C/ mins to form the hematite, Fe2O3, used as a raw powder to prepare SrFe12O19. Microstructure of Nd-doped strontium ferrites, Sr1-xNdxFe12O19, with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5, were prepared through a mechanical alloying technique. Several characterizations have been done, such as X-ray Diffraction (XRD) and Field emission scanning electron microscopy (FESEM). The magnetic properties of coercivity (Hc) and the energy product BHmax of samples are carried out. The magnetic properties of samples were investigated with an expectation of enhancing the magnetic properties by substitutions of Nd3+ ions on Fe3+ ion basis sites. The saturation magnetization Ms revealed magnetic behavior with respect to Nd3+ doping concentration, showing a decrease. The coercivity Hc increased with increasing Nd3+ doping concentration

Synthesis and characterization of magnetic properties of hard/soft nanocomposite permanent magnets

We report on an investigation of the magnetic properties of nanocomposite ferrite via different technique. Magnetic hard and soft ferrite, SrFe12O19/ Ni0.5Zn0.5Fe2O4 nanocomposites with mass ratio 4:1 were synthesised by using the mechanical alloying (750 rpm) method, physical mixing and high energy ball milling method. The nanocomposite ferrite was calcined at different temperatures from 500°C to 800°C to study the effect of calcination temperature on the magnetic properties of nanocomposite ferrite. The X-Ray Diffraction (XRD) result shows the double phase SrFe12O19 and Ni0.5Zn0.5Fe2O4 existed. The Transmission Electron Microscopy (TEM) image shows the particlesize is agglomerated, due to the attractive force. The magnetisation measurement was obtained at room temperature by using a Vibrating Sample Magnetometer (VSM). For mixing by mechanical alloying, nanocomposite ferrite at 800°C gives the larger value of magnetisation, Ms 46 emu/g which is higher than the Ms of a single phase of SrFe12O19, 37 emu/g. The remanence ratio, Mr/Ms of nanocomposite ferrite at 800°C gives the value more than 0.5, this proves that the exchange coupling exists with the higher value of Ms. For physical mixing, the highest magnetisation obtains are 51 emu/g at a temperature of 750°C. From this simple technique, we are able to attain good magnetic properties of nanocomposite ferrite nanoparticles with a particle size below 50 nm

Evolution of dielectric ceramic Ba6-3xNd8+2xTi18O54 (x=0.15) with microstructure at different sintering temperatures

The doping mechanism of neodymium ion on barium titanate could be promising a new material for applications in miniature microwave technology and mobile communication systems. Microstructural of Ba6-3xNd8+2xTi18O54, with x=0.15 ceramics at different sintering temperatures were investigated. The samples were prepared by the magnetic stirring method and sintered at a temperature range from 600°C to 1300°C. Sintering effects on the crystallite structure and surface morphology were studied and characterized by XRD and FESEM. The transformation of majority of the phase in the system from barium titanate to barium neodymium titanate was confirmed by XRD pattern due to change in sintering temperature. The change in sample densities was determined using Archimede’s method. Two activation energies of grain growth were observed by using estimated diffusion process. The activation energies were 0.0698 and 0.3348 eV for low sintering and high sintering temperatures respectively

Complex dielectric modulus and relaxation response at low microwave frequency region of dielectric ceramic Ba6-3xNd8+2xTi18O54

The desirable characteristics of Ba6-3xNd8+2xTi18O54 include high dielectric constant, low loss tangent, and high quality factor developed a new field for electronic applications. The microwave dielectric properties of Ba6-3xNd8+2xTi18O54, with x = 0.15 ceramics at different sintering temperatures (600–1300°C) were investigated. The phenomenon of polarization produced by the applied electric field was studied. The dielectric properties with respect to frequency from 1 MHz to 1.5 GHz were measured using Impedance Analyzer, and the results were compared and analyzed. The highest dielectric permittivity and lowest loss factor were defined among the samples. The complex dielectric modulus was evaluated from the measured parameters of dielectric measurement in the same frequency range, and used to differentiate the contribution of grain and grain boundary

Effect of PVP as a capping agent in single reaction synthesis of nanocomposite soft/hard ferrite nanoparticles

Nanocomposite magnets consist of soft and hard ferrite phases are known as an exchange spring magnet when they are sufficiently spin exchange coupled. Hard and soft ferrites offer high value of coercivity, Hc and saturation magnetization, Ms respectively. In order to obtain a better permanent magnet, both soft and hard ferrite phases need to be “exchange coupled”. The nanoparticles were prepared by a simple one-pot technique of 80% soft phase and 20% hard phase. This technique involves a single reaction mixture of metal nitrates and aqueous solution of varied amounts of polyvinylpyrrolidone (PVP). The heat treatment applied was at 800 °C for 3 h. The synthesized composites were characterized by Transmission Electron Microscope (TEM), Fourier Transform Infra-red (FT-IR), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD) and Vibrating sample magnetometer (VSM). The coexistence of two phases, Ni0.5Zn0.5Fe2O4 and SrFe12O19 were observed by XRD patterns. It also verified by the EDX that no impurities detected. The magnetic properties of nanocomposite ferrites for 0.06 g/ml PVP gives a better properties of Hc 932 G and Ms 39.0 emu/g with average particle size obtained from FESEM was 49.2 nm. The concentration of PVP used gives effect on the magnetic properties of the samples

DTA/TG, XRD and 27Al MAS NMR of yttrium aluminium garnet, Y3al5o12 by sol-gel synthesis

27Al magic angle spinning (MAS) NMR has been used at two fields (8.45 T and 14.1 T) to follow the optimisation of a sol-gel process to produce yttrium aluminium garnet, Y3Al5O12 (YAG), at moderate temperatures. 27Al MAS NMR is shown to be a highly sensitive tool to determine the presence of the impurity phase, yttrium aluminium perovskite, YAlO3. Single phase, polycrystalline YAG has been successfully synthesized, using this modified sol-gel process, at temperatures as low as 800◦C. Chemical shifts, quadrupolar coupling constants and asymmetry parameters are reported for the tetrahedral and octahedral aluminium sites of YAG