Papers by Keyword: Yttrium Aluminum Garnet

Abstract: Yttrium aluminum garnet (YAG) is an important material which require high temperature of 1600°C in its solid-state reaction. To lower this temperature, mechanical activation process has applied to the system which make the crystal arrangement broken thus make it more reactive. This process results in homogeneous and fine particle distribution of Al₂O₃ and Y₂O₃ compared to manually mixed powders. Moreover, milling process also reduce the particle size of the Al₂O₃ and Y₂O₃ from 4694 nm and 349 nm down to 274 nm. This also lessen the crystallite size of Al₂O₃ and Y₂O₃ from 1010 and 164 Å to 310 and 50 Å respectively. Then, after calcination at 1100°C, the milled powders form YAG phase in the opposite of manually mixed powders which form YAM phase. YAG formed have nearly round shape with finer grain compared to manually mixed powders which still has large grain of Al₂O₃ and Y₂O₃. This formation temperature is much lower than the require conventional solid-state reaction.

Abstract: Yttrium aluminum garnet is abbreviated as YAG, which has many excellent high temperature characteristics. YAG structural materials and functional materials are promising candidates. In this paper, YAG porous ceramic materials with different mechanical properties are prepared by adjusting the parameters of the sintering process to provide reference for the preparation of high-performance porous ceramics. From the experimental results, the following conclusions can be drawn: when the sintering temperature is 1450°C and the holding time is 2h, the YAG gradient porous ceramics have no deformation and shrinkage, have a regular good shape, and have good strength after sintering. The sintering rate was 8 °C/min and carbon emission temperature is 800°C, the structure of the YAG gradient porous material is good, the pores are uniform, and the strength of the sintered sample is high, The porosity is 25.7%, the compressive strength is 8.12MPa.

Abstract: This paper reports the quantitative characteristics of photoluminescence of phosphors powders based on yttrium-aluminium garnets. It contains spectra of excitation, spectra of luminescence with initiating through radiation of xenon lamps and chip with a different power, and kinetic characteristics.

Abstract: Finely-dispersed phosphors of Y₂O₃:Eu and Y₃Al₅O₁₂:Eu have been synthesized with the help of Pechini method and the method of self-propagating high-temperature synthesis (SHS). During the synthesis of phosphors on the basis of Y₂O₃ carried out with Pechini method the size of crystallites increases with the enlargement of concentration of yttrium, but it decreases when the method of SHS is applied. The structure of phosphors on the basis of Y₃Al₅O₁₂ (YAG) is strongly amorphized. This fact agrees with the data of XRD and with the prevalence of the band with λ_max = 613 nm in the spectra of this phosphor. The enlargement of yttrium concentration in it promotes the amorphisation of yttrium aluminum garnet and the decrease of a crystal phase content. The sample of Y₃Al₅O₁₂:Eu synthesized with Pechini method has the maximum intensity, while in conditions of excitement with “high-level” X-ray radiation which corresponds to the radiation of industrial medical X-ray apparatus, the phosphor of Y₂O₃:Eu synthesized with the help of SHS showed the largest intensity. Colloid solutions prepared with the use of the samples synthesized by SHS method revealed a higher steadiness and a lower disposition to the sedimentation process. The samples of Y₂O₃:Eu phosphor possessing the smallest size of particles and the highest intensity of X-ray luminescence are the most suitable for the creation of pharmacological drugs used for photodynamic therapy.

Abstract: In this paper, yttrium aluminum garnet-magnesium aluminate spinel with good mechanical strength was fabricated by directional solidification, and its microstructure and mechanical properties were investigated. MgAl₂O₄-Y₃Al₅O₁₂ eutectic rods were grown by a float zone method. The composition of the grown ingots was determined by the X-ray diffraction technique and electron probe microanalysis. The crack growth characteristics were examined in directionally solidified YAG/spinel eutectics. The residual stresses were determined in MgAl₂O₄/Y₃Al₅O₁₂ eutectics using piezospectrosocopic probes. The crack growth behaviors show that residual stresses play a key role in the crack growth.

Abstract: In the present work, compressive creep characteristics of directionally solidified MAS-YAG (MgAl₂O₄/Y₃Al₅O₁₂) were investigated at high temperature. The compressive creep strength of a crystal grown at a rate of 5 mm/min and a flow rate of 1.2 mm/min at 1500 °C under a strain rate of 1.0 × 10^-4 was only 400 MPa, which is slightly higher than that of crystals grown under different conditions. The compressive creep strength of an oxide eutectic fabricated by the directional solidification method is higher than that of a polycrystalline sintered eutectic with the same composition. The creep behavior at high temperature was studied and the mechanisms of deformation by dislocation motion were revealed by Transmission Electron Microscopy (TEM) observations.

Abstract: Yttrium aluminum garnet (YAG) with a chemical composition of Y₃Al₅O₁₂ is an important advanced structural and functional material.The preparation conditions were a pH of 9, a titration rate of 10ml/minute and a reaction time of 60 minutes. The analysis shows that the YAG precursor does not have an obvious characteristic crystalline diffraction peak, the characteristic diffraction peak of YAG was found after the calcination of the YAG precursor at 1100¡æ for 1 hour, the characteristic diffraction peak of YAG is strong, which indicates that the YAG crystalline phase is integrated and pure. The pore microstructure of porous YAG ceramics marked differed with an increase in the sintering temperature, the compressure strength of porous YAG ceramics is increased with an increase in the sintering temperature, the compressure strength shows the opposite rule with the prosity, which indicaties the mechanical properties of materials are effacted with the densification effect of materials.

Abstract: Ultrafine spherical yttrium aluminum garnet (YAG) powders have been synthesized via homogeneous precipitation method using urea as the precipitant. The precursor powders were calcinated at 1000°C or 1100°C for 4 hrs and then were studied by means of FE-SEM, XRD, FT-IR and TG-DTA. The result shows that the amount of ammonium sulfate has a significant effect on morphology and particle size of powders. Pure phase and spherical YAG particles with 350 nm in diameter can be obtained when the molar ratio of ammonium sulfate to aluminum nitrate is about 0.75 and the concentration of the metallic ions is 0.008M.

Abstract: Submicron single-phase yttrium aluminum garnet (Y₃Al₅O₁₂, YAG) powders were fabricated by solid-state reactive heat-treating a mixture of pyrolysis product, heat-treating isopropyl aluminum at 500°C, and yttria (Y₂O₃) powders. The powders were mixed by ball milling for 2~3 h doped with 5wt% aluminium fluoride (AlF₃), and then heat-treated at 1200°C for 2~5 h. Characterized by XRD, mixing the powders by ball milling and doped with AlF₃ lowered the heat-treating temperature and made the forming of YAG phase be single.

Abstract: This study used numerical simulation to investigate the growth conditions of yttrium aluminum garnet (YAG) single crystals by the vertical Bridgman method, and discusses the process performed with or without the installation of a submerged heater (SH). The maximum flow velocity of the melted material surrounding the melt/crystal interface can be decreased, and the deflection of the melt/crystal interface can be changed under various furnace temperature gradients and distances. The minimum of the maximized flow rate indicates that the natural convection can be decreased and controlled. In this manner, the growth rate of crystals increases in an identical environment.