Characterization of Aluminum-Substituted Yttrium-Iron Garnet Nanoparticles Prepared Using the Sol-Gel Technique

This project presents preparation and characterization of aluminum substituted yttrium iron garnet (Al-YIG) nanocrystalline powders of compositional variation of Y3.0-xAlxFe5O12, where x was 0, 0.5, 1, 1.5, 2, 2.5 and 3. The samples were synthesized using sol–gel technique. The starting raw materials used to prepare Al-YIG samples were aluminum nitrate (Al(NO3)3.9H2O), yttrium nitrate (Y(NO3)3.6H2O) and iron nitrate (Fe(NO3)3.9H2O). They were weighed according to the formula above, then mixed and dissolved together in solution of citric acid (C6H8O7.H2O) for a month to form the gel form by using magnetic stirrer equipment at 350 r.p.m at room temperature. The sample was then dried at 110oC in an oven for a day to remove the unneeded water before it was calcined and crushed to obtain fine particles powder. The calcined powder at 600oC, 700oC, 800oC, 850oC and 900oC respectively, were characterized by x-ray diffraction analyzer (XRD) to confirm the garnet phase. All samples were characterized also by RF-Impedance (1 MHz-1.8 GHz) to investigate the magnetic properties. Finally, field emission scanning electron microscopy (FESEM) and energy dispersive x-ray analyzer (EDX) were used to study the surface morphology and the elemental analysis of Al-YIG samples. The results showed that, the best garnet phase appeared when the sintering temperature was 800oC and Al-YIG nano-crystalline samples with high purity and sizes ranging from 20 to 100 nm were obtained. The magnetic measurement results of Al-YIG samples prepared by sol-gel method, gave high values of real permeability, the highest value of 5.29 was given by Y3Fe5O12 sample at about 80 MHz which was attributed to the large grain size, the highest magnetic permeability observed was due to easy movement of domain walls; and it shifted to the high frequency with increasing the amount of aluminum. The widest useful working frequency range appeared for Y3Fe5O12 sample and, also shifted to reach high range with increasing the concentration of aluminum

Electromagnetic Characterization Of Sm-Yig And Sm-Yig-Pvdf Composites Prepared Using Modified Conventional Mixing Oxide Technique

Samarium substituted-yttrium iron garnet (Sm-YIG) nanoparticles were fabricated via a modified conventional mixing oxides (MCMO) method according to the Y3-xSmxFe5O12 system (0 ≤ x ≤ 3). In this research, utilization of an organic compound (ethanol) and metal oxides in conjunction with mixing the reactants directly without adding water are the key techniques of this method. Using ethanol solution instead of water could produce nanoparticles with better homogeneity and smoother surface structure. Single-phase garnet structure of Sm-YIG nanoparticles was produced at 1350 0C sintering temperature with an average particle size ranged from 25 to 39 nm. XRD results of Sm-YIG samples at x = 2 and 2.5, presented some unknown peaks which speculated to, the time or/and sintering temperature is/are not enough to form the garnet structure phase of the samples. The true density values of 5.245 and 6.221 g.cm-3 were calculated for pure yttrium iron garnet (YIG, x=0) and samarium iron garnet (SmIG, x=3) samples, respectively which reached around 99% of the theoretical density of the samples. Real permittivities of the Sm-YIG samples presented almost flat values ranged from 7 to 10 with loss factors around 0.1 to 0.3, for YIG (x=0) and SmIG (x=3) respectively, within 10 MHz to 1 GHz frequency range. The real permeability value 19.5 is presented by pure YIG at 13.4 MHz and declined rapidly to be around 2 at 1 GHz, and decreased with increasing x. The higher permeability resulted in lower permittivity and vice versa for all the Sm-YIG samples. This work was also carried out to prepare the 10 wt% Sm-YIG in Poly-vinylidene-fluride (PVDF) composite samples and study their electromagnetic properties. Sm-YIG samples prepared via MCMO method, PVDF powder and Ethyl-methyl-ketone (MEK) were used to prepare such composites. High permittivities of composite samples observed at lower frequency range indicated to the heterogeneous conduction in the multiphase structure of the composites. The real permeabilities presented almost flat values through all the range of the frequency from 10 MHz to 1 GHz, with value of 1.06 at x=0 and 1.13 at x=3, for 10 wt% Sm-YIG loading in the composites. MCMO technique appears to be another alternative to the conventional (manufactured) technique, due to the decreasing of the particle size with better homogeneity, high purity, reduction of the cost, and high yield in a nano-scale product compared to other preparations techniques. The numerical optimization method performed using MATLAB program is to estimate the effective complex permittivity and/or permeability of each component of the 10 wt% Sm-YIG-PVDF composite samples. It is found that, the optimum impedance values are very close to the measured ones for each composite. The optimized values of the complex permittivities and permeabilities for both components [Sm-YIG and PVDF] are within the estimated ranges. The optimization process eliminated the difference between the measured impedance and the calculated one from Maxwell-Garnett (MG) formula via a specific objective function. Results of a developed formula based on MG formula with a comparison of various theoretical models including the MG, Looyenga, Bruggeman and Sen-Scala-Cohen, have been carried out and discussed with comparisons to the measurements for the 10 wt% Sm-YIG-PVDF composite samples. This was to calculate the complex permittivity and permeability of such composite materials. The lowest mean error percentage values were detected from the developed MG formula for each composite, which was different from composite to composite depend on the mole fraction x. The developed MG model appears to add a new contribution to the theoretical models to calculate the effective permittivity and permeability of mixture ferrite-polymer materials, due to its accuracy as compared with others

Preparation of samarium iron garnet nanoparticles via modified conventional mixing oxides method

This work is concerned with the preparation of samarium iron garnet (Sm3Fe5O12) nanoparticles via an improved technique named: Modified Conventional Mixing Oxides (MCMO) method. This material was characterized by XRD, FESEM, EDX and TEM. Metal oxides and ethanol solution were used as raw materials to prepare Sm3Fe5O12 (SmIG) material. Single-phase SmIG nanoparticles with an average particle value of 25 nm and average crystallite size value of 44 nm have been synthesized at 1350 °C via the MCMO method. SmIG powders with grain sizes below 1 μm and high purity have been presented by FESEM and EDX results, respectively. Lattice constant value of 12.535 A° and density value of 6.221 g.cm-3, were calculated for the SmIG sample. The latter has reached around 99% of its theoretical density. The MCMO method appears to be an attractive route due to the enhancement of structural properties of the interested sample with high yield in the nano-scale product as compared to other preparation techniques

Garnet ferrite (Y3Fe5O12) nanoparticles prepared via modified conventional mixing oxides (MCMO) method

This paper is presented an improvement in the conventional mixing oxides method as a way of trying to improve the manufactured technique to prepare ferrite materials. In this study, yttrium iron garnet (YIG) nanoparticles was synthesized by a modified mixing oxides (MCMO) method. In this research, utilization of an organic compound (ethanol) and metal oxides in conjunction with mixing the reactants directly without adding water are the key techniques of this method. The sample powder was characterized by using x-ray diffraction (XRD) to confirm the garnet phase. Microstructure observation of the sample has been carried out via field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Well defined single-phase garnet structure, with an average particle size of 39 nm was formed at 1350 °C. Density value of 5.245 g.cm-3, was calculated for YIG sample, which is reached around 99% of its theoretical density. MCMO technique appears to be another alternative to the conventional (manufactured) technique, due to the decreasing of the particle size with better homogeneity, high purity, reduction of the cost, and high yield in a nano-scale product compared to other preparations techniques

Preparation and characterization of aluminum substitute yttrium iron garnet nanoparticles by sol–gel technique

This paper presents preparation and characterization of aluminum substituted–iron garnet (Al-YIG) nanocrystalline powder. The samples were synthesized using sol–gel technique. The gel was prepared from Al(NO3)3.9H2O, Y(NO3)3.6H2O and Fe(NO3)3.9H2O. They were mixed and dissolved together in C6H8O7.H2O for a month to formation the gel form by magnetic stirrer equipment at 350 rpm. The sample was then dried at 110⁰C in an oven for a day to remove the unneeded water before it was calcined and crushed to obtain a fine particles powder. The calcined powder at 700⁰C, 750⁰C, 800⁰C, 850oC and 900⁰C was characterized by X-ray diffraction analysis (XRD) to confirm the garnet and the best garnet phase. Finally, Scanning Electron Microscopy (SEM) was used to study the morphology of sample. The results showed that, the best garnet phase appeared when the sintering temperature was 800⁰C and (Al-YIG) nanocrystals with sizes ranging from 50 to 100 nm were formed

Preparation and characterisation of PVDF Sr₂.₅Yₒ.₅Fe₅O₁₂ particles composite

Polyvinylidene fluoride (PVDF)-Sr2.5Y0.5Fe5O12 (SrYIG) particles film is investigated under scanning electron microscopy (SEM) technique for its surface morphology and physical compatibility studies. Films were prepared via powdersolution- gel-film phases with magnetic stirring at about 200 r.p.m and heating at about 90°C for 1 hour before the hot gel is poured into a dish for formation of thick film followed with atmospheric cooling for another 24 hours. Four samples were prepared with different SrYIG filler content of 0, 1, 5 and 10 wt%. The thick films were coated with gold for SEM analysis. SEM images were taken with JEOL 6400 scanning electron microscope and energy dispersive X-ray (EDX) analyses were also done with the same equipment. Magnetic characteristics were done on Agilent 4291B RF Impedance/Material Analyzer from 1MHz to 1.8GHz. SEM images showed that PVDF in cyclopentanone has surface that is relatively smooth. PVDF with magnetic fillers lost its smoothness and have granulated-like surface morphology instead. There is no clear evidence that the PVDF rejected the magnetic fillers though EDX analysis does not show existence of magnetic particles in the PVDF films. Magnetic properties of PVDF films were reduced when SrYIG fillers were introduced into the films

Formation of carbon nanotubes catalyzed by metal and bi-metal via pulsed laser depositon technique

Carbon nanotubes were formed by laser ablation using graphite containing a metal and bi-metal catalyst as a target. The Nd:YAG laser with 532 nm wavelength, 10.54 W was used to irradiate the target to form the carbon nanotubes. The pressure inside the chamber was kept at 4 Torr. Web-liked carbon nanotubes were found on the substrate after 30 minutes laser irradiation. The SEM images showed that the diameter of the carbon nanotubes formed by metal and bi-metal catalyst in the ranging 35-150nm. The yield of carbon nanotubes depended on the metal catalyst, NiCo was found is an effective catalyst for the growth of Carbon nanotubes

Formation of carbon nanotubes catalyzed by metal and bi-metal via pulsed laser depositon technique

Carbon nanotubes were formed by laser ablation using graphite containing a metal and bi-metal catalyst as a target. The Nd:YAG laser with 532 nm wavelength, 10.54 W was used to irradiate the target to form the carbon nanotubes. The pressure inside the chamber was kept at 4 Torr. Web-liked carbon nanotubes were found on the substrate after 30 minutes laser irradiation. The SEM images showed that the diameter of the carbon nanotubes formed by metal and bi-metal catalyst in the ranging 35-150nm. The yield of carbon nanotubes depended on the metal catalyst, NiCo was found is an effective catalyst for the growth of Carbon nanotubes