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1.
Bruce King Yin Liu Suresh Baskaran Richard Laine John Halloran 《Particulate Science and Technology》1992,10(3):121-132
Yttrium aluminum garnet (YAG - Y3Al5O12) fibers have been prepared by dry spinning solutions of yttrium and aluminum carboxylate polymers (precursor route) and by dry spinning aqueous oxide sols (sol-gel route). Fibers from aqueous diphasic gels are prepared by mixing a colloidal alumina sol containing 50-nm hydrous alumina with a colloidal yttria sol containing 10-nm yttrium oxide, using polyvinylpyrrolidone as a spinning aid. Fibers by the precursor route are made from spinnable THF solutions of yttrium isobutyrate and aluminum isobutyrate or from aqueous solutions of polymeric aluminum formate and yttrium acetate.
The isobutyrate materials decompose between 200-400°C to an amorphous residue. Crystallization occurs abruptly between 875°C and 900°C, forming the YAG phase directly. The formate-acetate also decomposes to amorphous residues, which form YAG at 900°C. In the diphasic gel, YAG forms gradually between 1000 and 1200°C, with intermediate products YAP (YalO3 perovskite) and/or YAM (Y4Al2O9 monoclinic). At 1500°C, single phase YAG is obtained as pore-free fibers with 500 nm grains. 相似文献
The isobutyrate materials decompose between 200-400°C to an amorphous residue. Crystallization occurs abruptly between 875°C and 900°C, forming the YAG phase directly. The formate-acetate also decomposes to amorphous residues, which form YAG at 900°C. In the diphasic gel, YAG forms gradually between 1000 and 1200°C, with intermediate products YAP (YalO3 perovskite) and/or YAM (Y4Al2O9 monoclinic). At 1500°C, single phase YAG is obtained as pore-free fibers with 500 nm grains. 相似文献
2.
《Composites Part A》2001,32(8):1127-1131
Polycrystalline yttrium–aluminum garnet, Y3Al5O12 (YAG) fiber and α-alumina and YAG matrix composite fiber were prepared by the sol–gel method. α-Alumina and YAG matrix composite fiber with fine and homogeneous microstructure could be successfully fabricated by interpenetrating YAG in alumina matrix and adding α-alumina of seed particles to fibers. Effect of α-alumina seed particles and YAG on crystallization and microstructure of composite fiber were discussed. The size of alumina matrix of the composite fibers heated at 1600°C for 4 h was below 2 μm. The tensile of strength alumina fiber heat-treated at 1500°C was 0.2 GPa, while that of the composite fiber was 1.1 GPa. 相似文献
3.
Well-dispersed nano-crystalline transition alumina suspensions were mixed with yttrium chloride aqueous solutions, with the aim of producing by spray-drying Al2O3–Y3Al5O12 (YAG) composite powders of increasing YAG vol.%. Two samples were prepared, with different Y content, corresponding to 5 and 20 YAG vol.%, respectively. Both samples were then treated at either 600 or 1150 °C. The obtained powders were characterized by X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infra Red (FT-IR) spectroscopy and compared to three reference samples: commercial nano-crystalline transition alumina, YAG and Y2O3. YAG powders were obtained by co-precipitation route whereas Y2O3 powders were yielded by spray-drying of a yttrium chloride aqueous solution. Modification of physico-chemical properties of the surface of alumina nanoparticles were assessed by combining XPS and FT-IR spectroscopies. On the basis of the results obtained, a possible model is proposed for the structure of the obtained composites, in which Y basically reacts with more acidic hydroxyls of alumina, by forming Y-rich surface grains, the extension of which depends on the thermal treatment. 相似文献
4.
Yukiya Hakuta Tsukasa HaganumaKiwamu Sue Tadafumi AdschiriKunio Arai 《Materials Research Bulletin》2003,38(7):1257-1265
Phosphor YAG:Tb ((Y2.7Tb0.3)Al5O12) nano particles were synthesized by a hydrothermal method at supercritical conditions (400 °C and 30 MPa) using a flow reactor. Hydroxide sol solutions formed by stoichiometric aluminum nitrate, yttrium nitrate, terbium nitrate and potassium hydroxide solutions. The relationship between particle size and experimental variables including pH, concentration of coexistent ions and hydroxide sol were investigated. Particles were characterized by XRD, TEM and photo-luminescence measurements. Particle size of YAG:Tb became finer as pH was increased or potassium nitrate concentration of the starting metal salt solution was increased. By removing the coexisting ions (NO3−, K+) from the metal salt solution, single phase YAG:Tb particles with 20 nm particle size were obtained. The emission spectra of YAG:Tb particles of 14 nm shows a blue shift. 相似文献
5.
Ultra-Small YPO4-YAG:Ce Composite Nanophosphors with a Photoluminescence Quantum Yield Exceeding 50%
Yige Yan Adel Mesbah Lhoussain Khrouz Corinne Bouillet Chantal Lorentz Nicholas Blanchard Anne C. Berends Marie Anne van de Haar Frédéric Lerouge Michael R. Krames Ovidiu Ersen Frédéric Chaput Stephane Parola 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(26):2208055
Synthesis of high quality colloidal Cerium(III) doped yttrium aluminum garnet (Y3Al5O12:Ce3+, “YAG:Ce”) nanoparticles (NPs) meeting simultaneously both ultra-small size and high photoluminescence (PL) performance is challenging, as generally a particle size/PL trade-off has been observed for this type of nanomaterials. The glycothermal route is capable to yield ultra-fine crystalline colloidal YAG:Ce nanoparticles with a particle size as small as 10 nm but with quantum yield (QY) no more than 20%. In this paper, the first ultra-small YPO4-YAG:Ce nanocomposite phosphor particles having an exceptional QY-to-size performance with an QY up to 53% while maintaining the particle size ≈10 nm is reported. The NPs are produced via a phosphoric acid- and extra yttrium acetate-assisted glycothermal synthesis route. Localization of phosphate and extra yttrium entities with respect to cerium centers in the YAG host has been determined by fine structural analysis techniques such as X-ray diffration (XRD), solid state nuclear magnetic resonance (NMR), and high resolution scanning transmission electron microscopy (HR-STEM), and shows distinct YPO4 and YAG phases. Finally, a correlation between the additive-induced physico-chemical environment change around cerium centers and the increasing PL performance has been suggested based on electron paramagnetic resonance (EPR), X-ray photoelectron spectrometry (XPS) data, and crystallographic simulation studies. 相似文献
6.
《Vacuum》2013
Interactions between Y2O3–Al mixture studied by solid-state reaction method were investigated in present paper. Interactions between Y2O3–Al mixture was characterized by differential thermal and thermogravimetric analyses and X-ray diffraction, Y2O3–Al mixture and yttrium aluminum garnet (YAG) powder as final reaction product were characterized by scanning electron microscopy. The results show Al is isolated with Y2O3 by aluminum oxide layer in air, and no opportunity of directional reaction between Y2O3–Al systems. With temperature increasing to ∼569 °C, aluminum partly turned into transitional aluminas, Y2O3 reacts with transitional aluminas instead of aluminum to form yttrium aluminum monoclinic (YAM) and yttrium aluminum perovkite (YAP) phases after calcination at 600 °C, 800 °C separately, and pure YAG powder is obtained after calcination at 1200 °C. From the point of view of reaction temperature, the reaction between Y2O3 and transitional aluminas is easier than that of Y2O3 and Al or α-Al2O3. 相似文献
7.
《Advanced Powder Technology》2014,25(1):450-456
Y-doped ultrafine AlN powders were synthesized by a carbothermal reduction nitridation (CRN) route from precursors of Al2O3, C and Y2O3 prepared by a sol–gel low temperature combustion technology. The Y dopant reacted with alumina and thus forming yttrium aluminate of AlYO3, Al3Y5O12 and Al2Y4O9, which formed a liquid at about 1400 °C and promoted the transformation of Al2O3 to AlN and the growth of AlN particles. Compared with the conventional solid CRN process, Y dopant reduced the synthesis temperature by 150 °C, and Al2O3 transformed to AlN completely at 1450 °C. The content of Y dopant had little effect on the synthesis temperature of AlN whereas it influenced the phase of Y compounds in the products. As the Y/Al molar ratio was in the range of 0.007648–0.022944, the particle sizes of Y-doped AlN powders synthesized at 1450 °C were 150–300 nm. 相似文献
8.
T. Yu. Kolomiets G. B. Tel’nova A. A. Ashmarin V. I. Chelpanov K. A. Solntsev 《Inorganic Materials》2017,53(8):874-882
Using high-temperature X-ray diffraction, differential scanning calorimetry, and electron microscopy, we have studied the formation of yttrium aluminates and Nd:YAG (YAG) activated garnet nanoparticles during the thermal decomposition of a poorly crystallized carbonate precursor prepared in the NH4Al(OH)2CO3–(Y,Nd)(ОН)CO3 nanosystem and the development of the morphological structure of powders during heating to a temperature of 1350°C. The results demonstrate that heat treatment in the temperature range 850–950°C leads to the formation of metastable nonstoichiometric YAlO3 with a garnet-like structure, which reacts with Al2O3 at a temperature of 1000°C to form YAG. The cubic cell parameter a and X-ray density of YAG crystals with the composition Y2.97Nd0.03Al5O12 synthesized at 1200°C are 1.2009 nm and 4.565 g/cm3, respectively, and the average particle size is 108 nm. Using carbonate route, we prepared transparent Nd:YAG ceramics with a relative density of 99.7%, X-ray density of 4.562 g/cm3, and crystallite size in the range 1–7 μm. 相似文献
9.
Continuous alumina gel fibres were prepared by sol–gel method. The spinning sol was prepared by mixing aluminum nitrate, lactic acid and polyvinylpyrrolidone with a mass ratio of 10:3:1· 5. Thermogravimetry–differential scanning calorimetry (TG–DSC), Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibres. The Al2O3 fibres with a uniform diameter can be obtained by sintering gel fibres at 1200 °C. 相似文献
10.
M. G. Ivanov Yu. L. Kopylov V. B. Kravchenko K. V. Lopukhin V. V. Shemet 《Inorganic Materials》2014,50(9):951-959
Undoped and Nd- or Yb-doped laser-grade yttrium aluminum garnet and (Y,La)2O3 ceramics with a transmittance above 80% in the 1-μm lasing region have been prepared by solid-state reactions using nonagglomerated Y2O3 and Al2O3 nanopowders. The Y2O3 nanopowders were prepared via laser evaporation, chemical precipitation from urea solutions, and grinding of commercially available Y2O3 in a purposedesigned laboratory-scale attritor at stirrer rotation rates of up to 1500 rpm. The YAG ceramics were prepared using commercially available Al2O3. After grinding, all of the powders had a particle size on the order of a hundred nanometers. Green compacts produced from the nanopowders were sintered in a vacuum furnace between 1615 and 1750°C to give highly transparent ceramic samples. 相似文献
11.
O. P. Krivoruchko T. V. Larina A. V. Ishchenko E. V. Pestryakov M. A. Merzliakov 《Inorganic Materials》2017,53(5):540-547
This paper presents results of a detailed study of fundamental aspects of the formation of 2D and 3D nanostructured YSZ:Yb3+ ceramics with a cubic structure through a key synthesis step in aqueous solutions of zirconium-containing hydroxy nanoparticles (1–2 nm) modified by Y3+ and Yb3+ ions, with the use of a sol–gel method and subsequent calcination of the resultant xerogels at temperatures above 350°C. As starting chemicals for the synthesis of ceramic powders, we used zirconyl, yttrium, and ytterbium nitrates and chlorides and aqueous ammonia. Using mixed solutions of these salts and a procedure developed by us, we synthesized sols, gels, and xerogels. To examine the effect of temperature on solid-state transformations, the xerogels were calcined according to a predetermined program in a muffle furnace at temperatures in the range from 350 to 1350°C (rarely, up to 1650°C). We focused primarily on ceramic powders close in composition to 0.86ZrO2 · 0.10Y2O3 · 0.04Yb2O3. The ceramics were characterized by high-resolution transmission electron microscopy, electron microdiffraction, electronic diffuse reflectance spectroscopy, energy dispersive X-ray microanalysis, and X-ray fluorescence analysis. 相似文献
12.
《Materials Letters》2005,59(2-3):355-360
The Al2O3–ZrO2(Y2O3) composite powder was synthesized through a sol–gel process using aluminum sec-butoxide and zirconium butoxide as precursors. The as-received powders in an amorphous phase were crystallized with c-ZrO2 at around 980 °C. As the calcination temperature increased, the c-ZrO2 crystalline phase was transformed to t-ZrO2 at about 1200 °C. However, the Al2O3 phase in the Al2O3–ZrO2(Y2O3) composite powders still existed in an amorphous phase up to 1050 °C. In the sintered body using the calcined powders at 400 °C, the Al2O3 phase was crystallized in an α-phase at 1200 °C during the sintering for 2 h. Using the sol–gel Al2O3–ZrO2(Y2O3) powder, a typical nano-composite having a nano-crystalline phase (less than 20 nm) can be successfully obtained by a pressureless-sintering process even at 1200 °C for 2 h.Using the sol–gel Al2O3–ZrO2(Y2O3) powder, a typical nano-composite having a nano-crystalline phase (less than 20 nm) can be successfully obtained by a pressureless-sintering process even at 1200 °C for 2 h. The values of relative density and Vickers hardness were comparatively high value with about 96.2% and 1100 Hv, respectively, even though it was made at low temperature. In the composite sintered at 1400 °C, the hardness value was saturated with 1570 Hv and the values of fracture toughness were almost same with about 6 MPa m1/2. 相似文献
13.
Nonhydrolytic sol-gel synthesis and characterization of YAG 总被引:1,自引:0,他引:1
Eduardo José Nassar Paula Fabiana dos Santos Pereira Evelisy Cristina de Oliveira Nassor Lilian Rodrigues Ávila Katia Jorge Ciuffi Paulo Sergio Calefi 《Journal of Materials Science》2007,42(7):2244-2249
Yttrium–aluminum oxides are interesting compounds, which are widely used as hosts for lasers and phosphors due to their stable
physical and chemical properties. The manufacture of YAG has been investigated thoroughly. YAG powders are traditionally synthesized
through the reaction of aluminum and yttrium powders at high temperatures. The work reported here involved an investigation
into the preparation of YAG by a nonhydrolytic sol-gel route and the influence of heating time at low temperatures to obtain
YAG from inorganic precursors (yttrium and aluminum chloride). AlCl3, YCl3 and ethanol were reflux reacted under an argon atmosphere. Europium III chloride was added as a structural probe. The powder
was treated at 800 °C for 1, 2, 4, 8 and 16 h. The YAG structure was analyzed by X-ray diffraction (XRD), nuclear magnetic
resonance (NMR), thermal analysis (TA) and photoluminescence (PL). The XRD revealed only peaks corresponding to the YAG phase.
PL data showed that the YAG phase was formed in 2 min with samples pretreated at 50 °C. For the samples pretreated at 800 °C,
the YAG phase appeared in 30 s. The excitation spectra presented a maximum of 394 nm corresponding to the 5L6 level, while the emission spectra of Eu III ions showed characteristic transition bands arising from the 5D0 → 7F
J
(J = 1, 2, 3, 4) manifolds at maximum excitation. The magnetic dipole 5D0 → 7F1 transition exhibited greater intensity than the electric dipole 5D0 → 7F2 transition. This methodology proved efficient for obtaining YAG phase. 相似文献
14.
Kazuaki Kanai Yoshifumi Fukui Takahiro Kozawa Akira Kondo Makio Naito 《Advanced Powder Technology》2017,28(1):50-54
Here, we report on the effect of BaF2 powder addition on the mechanical synthesis of Ce3+-doped Y3Al5O12 (Y2.97Al5O12:Ce0.033+, YAG:Ce3+) phosphors for white light emitting diodes. The YAG phosphors were synthesized by the mechanical method using an attrition-type mill. When BaF2 was added at 6 wt% to the raw powder materials and milled, the synthesis of YAG:Ce3+ was favorably achieved at the vessel temperature of 255 °C, which was about 1200 °C lower than the YAG phosphor synthesis temperature by solid-state reaction. The synthesized YAG:Ce3+ phosphor revealed the maximum internal quantum yield of 57%. 相似文献
15.
Sub-micrometer-sized powders of Y3Al5O12:Tb phosphor (dSEM = 320 nm) were prepared by flame-assisted spray pyrolysis of aqueous precursors in a premixed propane/air flame and in situ deposited onto quartz substrates. Phosphor screens with densities of up to 0.7 mg cm−2 could be produced within 20 min. As-deposited coatings were amorphous and required a thermal post-treatment. After annealing in an oven for 2 h (T ≥ 900 °C), the yttrium aluminum garnet phase (YAG:Tb) was obtained. Alternatively, the phosphor coatings were treated by an impinging flame in the same setup used for the deposition. Quasi-amorphous Y3Al5O12:Tb coatings demonstrated bright green photoluminescence upon flame annealing at T ≈ 1100 °C for just several minutes and could outperform YAG:Tb when excited in the wavelength ranges 205–220 nm and 230–260 nm. For example, brightness of emission from the quasi-amorphous coatings was up to five times higher than that of the fully crystalline YAG:Tb phosphor at a technically important wavelength of 254 nm. 相似文献
16.
J. Wojewoda-Budka N. Sobczak B. Onderka J. Morgiel R. Nowak 《Journal of Materials Science》2010,45(8):2042-2050
The systematic microstructure and thermodynamic studies of the reactions between liquid aluminum and dense polycrystalline
yttria (Y2O3) substrates at 1,273 K are reported in this article. The microstructure observations showed the presence of three reaction
product zones extending ~1 mm into the oxide substrate of typical C4 (Co-Continuous-Ceramic-Composites) structure. The first
zone starting from the drop side was composed of fine crystalline precipitates of the Al5Y3O12 (YAG) phase dispersed in the Al3Y matrix. The second zone was built of larger AlYO3 (YAP) crystals. The third zone formed elongated oxide precipitates (YAP) surrounded by the Al2Y intermetallic channels. The thermodynamic calculation indicated that, depending on the amount of the yttrium dissolved in
aluminum, the YAG (up to 5 at.% Y), YAP (5–13 at.% Y), or Al2Y for higher content of yttrium might form at 1,273 K, while the Al3Y phase might appear during cooling. 相似文献
17.
《Optical Materials》2014,36(12):2155-2159
Ce-doped Al2O3−YAG (Y3Al5O12, yttrium aluminum garnet) eutectic, a resin-free phosphor for white light emitting diodes (WLEDs), was successfully grown by the Czochralski method. X-ray diffraction and scanning electron microscopy show that this material has a typical eutectic structure of interpenetrating sapphire and garnet phases, as well as lamellar spacing in the order of tens of microns. The eutectic has a higher Ce3+ segregation coefficient than YAG single crystal. The photoluminescence properties of this eutectic were also investigated. Results show that it is characterized by a wide excitation band, and that the luminous efficiency of a eutectic-packaged LED is higher than that of a phosphor powder-packaged LED. The findings indicate that the Al2O3−YAG eutectic is a promising phosphor for WLED applications. 相似文献
18.
《Optical Materials》2005,27(1):21-27
Y2O3 optical planar waveguides are fabricated by the sol–gel method and the dip-coating technique. High purity yttrium alkoxide (yttrium 2-methoxyethoxide) is used as starting material for the Y2O3 sol and acetylacetone is added to improve the stability of the sol. Highly concentrated sol up to 0.8 M is prepared and six stacked layers are enough to support four propagation modes at wavelength from 488 to 632.8 nm. The cubic phase of Y2O3 is crystallized after an annealing treatment at 700 °C. X-ray diffraction is conducted on the films for their structural analysis. Optical properties of the waveguides are determined by multi-wavelength m-lines spectroscopy and attenuation coefficient measurement. The attenuation coefficient of the prepared Y2O3 waveguiding thin films is in the range between 1 and 2 dB/cm at 632.8 nm. 相似文献
19.
Compact, crack-free alumina film was fabricated using an alumina sol with a high Al2O3 content. With the addition of ethylacetoacetate (CH3COCH2COOC2H5, EAcAc), the stable sol could be prepared with a molar ratio of aluminum sec-butoxide (Al(O-sec-Bu)3, ASB) to water up to 1:25. It was found that EAcAc could notably decrease the surface tension of the liquid in the gel pores. The EAcAc modification layer on the colloidal particle retarded greatly the densification of the Al2O3 gel film and provided a long-lasting structural relaxation during heating. Therefore, the formation of cracks was effectively prevented in this alumina material. The alumina gel film contained a high Al2O3 content and there was a rather small mass loss during sintering. The critical thickness of Al2O3 sol-gel film was eight times higher than that could be achieved via the general sol-gel route and a film thicker than 0.8 μm was prepared by a single-step dipping operation. 相似文献
20.
An yttrium aluminum garnet (YAG) precursor precipitate was synthesized by urea method using yttria (Y2O3) and aluminum nitrate (Al(NO3)3·9H2O) as raw materials. The fresh wet precipitate was dried by supercritical carbon dioxide (CO2) fluid and the resulting powder was calcined at temperatures from 600 to 1600 °C. Crystallization of YAG was detected at 800 °C, and completed at 900 °C. HRTEM images of the YAG product obtained above 900 °C revealed crystallographically specific oriented attachment along the [1 1 2] direction. Based on the observation of the particle morphology a possible growth mechanism of YAG nanoparticles was presented. The fast increase on the average crystallite size of YAG at temperatures from 900 to 1300 °C is attributed to the crystallographically specific oriented attachment growth process. As the growth process proceeds at higher temperatures, oriented attachment based growth becomes less important because of the increase on particle size, and the self-integration assisted by the Ostwald ripening becomes dominant. 相似文献