Yttrium Iron Garnet Nanopowders Research Articles

Size-Dependent Magnetic and Magneto-Optical Properties of Bi-Doped Yttrium Iron Garnet Nanopowders

Bi-doped yttrium iron garnet nanopowders were successfully synthesized by a combustion method at different synthesis conditions, and the evolution of their structural, magnetic, and magneto-optical properties has been studied by various methods. X-ray diffraction analysis revealed that crystallite size increases with increase as in annealing time (tA) well as in annealing temperature (TA) and varied from 15.2 nm (TA = 650 °C, tA = 0.5 h) to 44.5 nm (TA = 800 °C, tA = 12 h). The magnetic hysteresis loops exhibit behavior characteristic of soft magnetic materials; herewith, the saturation magnetization demonstrates a growing trend with increasing crystallite size (D). The behavior of the coercivity indicates that, at room temperature, the transition between single-domain and multidomain states occurs at D = 35.3 nm. It was found that the size effect in the MCD spectra is clearly observed for the samples with crystallite sizes less than 42.2 nm for an intersublattice charge-transfer transition and a crystal-field tetrahedral transition. The influence of cation redistribution on the observed changes has been discussed.

Microwave-Assisted Synthesis of Yttrium Iron Garnet Nano Powders for Low Temperature Sintering

Yttrium iron garnet (YIG) nano powders have been successfully synthesized by a chemical co-precipitation plus microwave heating method. The particle sizes of the synthesized YIG powders ranged from 15 nm to 30 nm. Their heating behaviors indicated that small YIG nano crystallites in the synthesized powders started to melt and form liquid phase at a low temperature about 947°C. By using the synthesized powders as the starting materials, the dense YIG ceramics were sintered at the temperature of about 1050–1100°C, which was much lower than the sintering temperature for the powder derived from traditional solid reactions. The liquid phase from melting of small particles promoted the diffusion and re-crystallization, resulting in the low temperature sintering of YIG ceramics.

Structural and magnetic properties of Ni-doped yttrium iron garnet nanopowders

Abstract We present a study about the structural and magnetic properties of Ni-doped yttrium iron garnet nanopowders synthesized by sol-gel. The Rietveld refinement of the X-ray diffractograms indicates the replacement of Fe by Ni in the tetrahedral (d) and octahedral (a) sites of yttrium iron garnet (YIG) structure. The lattice parameter showed variation associated to the effects of Ni inclusion and structural defects, such as, oxygen vacancies. The morphological analysis evidence particles with a cylindrical shape and the Energy Dispersive Spectroscopy results corroborate the presence of Ni. The average porosity suggests that the replacement of Fe by Ni does not substantially change the textural properties of the particles. The Fourier transform infrared and Raman spectroscopies showed the characteristic absorption bands of YIG and confirmed the substitution in the a-sites and d-sites. The saturation magnetization was studied from the hysteresis loops measurements and present variations with the dopant concentration, associated to the replacement of Fe by Ni and to the oxygen vacancies occurrence. Changes in the coercive field for different dopant concentration were associated to the particle size and pinning centers existence.

An insight into formation mechanism of rapid chemical Co-precipitation for synthesizing yttrium iron garnet nano powders

The rapid chemical co-precipitation method is supposed to be a stable way to synthesize high quality cubic yttrium iron garnet (YIG) nanopowders. In this paper, focusing on clarifying its formation mechanism, the thermal behaviors and the elemental distributions of the chemical co-precipitated precursors have been analyzed by simultaneous differential scanning calorimetry plus thermal gravimetric analysis (DSC-TGA) and energy disperse spectroscopy (EDS) mapping technique on a transmission electronic microscope. The results indicated that the homogeneity of Y and Fe elemental distributions in the precursor powders determines the process through which the cubic YIG phase would form: one experiences the intermediate tetragonal YIG phase; the other takes YFeO3 as the intermediate phase. The homogenous distributions of Y and Fe elements in the precursor powders at the scale below 50 nm forms the intermediate tetragonal YIG phase rather than YFeO3, which leads to reduction of the formation temperature for synthesizing the single phase YIG. The obtained YIG nanopowders with the average particle size below 100 nm show excellent magnetic properties with saturation magnetization of 26 emu/g and coercive field of 45 Oe. This clear formation mechanism of YIG nanopowders is suitable for optimizing the processing conditions for the chemical precipitation synthesis of YIG nanopowders at large scale.

Synthesis of YIG Nanopowders by Sol-Gel Method

Yttrium iron garnet (YIG) nanopowders were synthesized by sol-gel method using Fe(NO3)3·9H2O, Y(NO3)3·6H2O as raw materials. The influence of heat treatment, the citric acid to metal nitrates molar ratio (CA / MN) and PH value on the synthesized powders were investigated using scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). YIG powders with average grain size of 80~90nm were synthesized after calcining at 1000°C for 4h.

Phase evolution and magnetic properties of Al substituted yttrium iron garnet nanopowders and plasma-sprayed coatings

Aluminum-substituted yttrium iron garnet (Al-YIG) nanostructured powders were synthesized using a citrate–nitrate gel combustion process. Atmospheric plasma-spray (APS) technique was employed to spray deposit the combustion derived feedstock powders. Nevertheless incongruently melting YIG resulted into a two-phase microstructure, Al-YIG powder resulted into a nanostructured garnet single phase when sprayed through thermal plasma. Room temperature saturation magnetization ( M S) and Curie temperature ( T C) of the Al-YIG powders decreased as a function of increasing Al content. As-sprayed YFe 3.8Al 1.2O 12 coating has a room temperature M S of 6.2 emu/cc and is increased to 7.3 emu/cc after post-deposition heat treatment at 1000 °C/1 h. Microstructural characteristics of single splats were analyzed in order to understand the feedstock effect on deposit.

Microwave-induced combustion synthesis of yttrium iron garnet nano-powders and their characterizations

Yttrium iron garnet nano-powders were successfully synthesized by microwave-induced combustion process. The process takes only 30 min to obtain as-received yttrium iron garnet nano-powders. The resultant powders annealed at different temperature and were investigated by XRD, SEM, VSM, TG/DTA and a surface area measurement.