YAG Nanopowders Research Articles

The influence of nonradiative relaxation on laser induced white emission properties in Cr:YAG nanopowders

The influence of nonradiative relaxation on laser induced white emission properties in Cr:YAG nanopowders

Synthesis and Characterization of Rare Earth doped YAG Nanopowders via Combustion Synthesis

Synthesis and Characterization of Rare Earth doped YAG Nanopowders via Combustion Synthesis

Influence of isomorphic substitution of Y3+ ions by Gd3+ ions on structural and luminescent properties of Yb:YAG nanopowders

In this work the influence of sequential isomorphic substitution of Y3+ by Gd3+ on crystal structure, morphology and luminescence spectra of (Y1−x−yGdxYby)3Al5O12 nanocrystals (size 30–40 nm) synthesized via low temperature polymer-salt method was investigated. Prepared nanopowders were studied by XRD, SEM methods of analysis, FT-IR and luminescence spectroscopy. The garnet cubic crystal structure of prepared nanoparticles remains at the replacement of 50% Y3+ by Gd3+ ions. The substitution of Y3+ ions by Gd3+ increases the volume of unit cell of garnet crystals and significantly disorders their crystal structure. It was shown that the controlled partial substitution (up to 50%) of Y3+ ions by Gd3+ in Yb:YAG materials leads to significant broadening of the main emission band of Yb3+ ions (λmax. = 1030 nm) that can be promising for development of ultrashort pulsed laser media.

Er:YAG/Yb:YAG nanopowders‐derived Er/Yb co‐doped yttrium aluminosilicate (YAS) fibers fabricated by UV‐curable nanocomposites for 1.5‐µm single‐frequency fiber lasers

AbstractThe rare‐earth (RE)‐doped yttrium aluminosilicate (YAS) glass fibers have demonstrated their unique advantages in single‐frequency lasers due to their high solubility of RE ions and high gain per unit length. However, the RE‐doped YAS fiber is usually fabricated by RE:YAG crystal or ceramic rods and melting‐in‐tube method, which depend heavily on RE:YAG crystal or ceramic rods and, thus, cannot adjust the fiber compositions effectively; there is little research on the multiple RE ions co‐doped YAS fiber deriving from RE:YAG crystal or ceramic rods. In present work, we developed a novel method to fabricate Er/Yb co‐doped YAS fibers efficiently. The Er:YAG and Yb:YAG nanopowders were fabricated by the coprecipitation method, and then the nanopowders were dispersed into liquid organic resin to form a novel UV‐curable nanocomposite, after curing, debinding, purifying, and drawing process, an Er/Yb co‐doped YAS fibers was fabricated, the absorption coefficients of the fiber was measured to be 17 dB/cm at 976 nm (2F7/2ground level to2F5/2level of Yb and4I15/2ground level to4I11/2level of Er) and 3.2 dB/cm at 1530 nm (4I15/2ground level to the high states of4I13/2of Er). A 1.5‐µm single‐frequency laser was constructed with the 2‐cm Er/Yb co‐doped YAS fiber. The longitudinal mode spacing was calculated to be 2.2 GHz with an effective cavity length of 4.5 cm, and the spectral signal‐to‐noise ratio was higher than 60 dB. To the best of our knowledge, it is the first time that Er/Yb co‐doped YAS fibers are fabricated using the UV‐curable nanocomposites. It indicates that this proposed technology is critical for the fabrication of various types of RE ions co‐doped YAS fibers and their applications in single‐frequency fiber lasers.

Preparation of YAG nanopowders and ceramics via coprecipitation: Effects of treatment modes of precipitates

Effects of treatment modes of precipitates in the coprecipitation method on the resulting YAG nanopowders and ceramics are investigated. Three treatment modes for precipitates, namely, single water washing, water–ethanol washing, and water washing–ethanol immersion, are conducted to prepare the YAG nanopowders. The average particle size (∼62 nm) and distribution (mainly ranging from 30 to 110 nm) of the powders obtained by the three modes are similar. However, the dispersity of the three powders shows large differences. The nanopowder obtained via water washing–ethanol immersion possesses optimal dispersity without any agglomeration, whereas that obtained via single water washing comprises substantially hard agglomerations. The relative density, Vickers hardness, and optical in-line transmittance of the ceramics prepared via water washing–ethanol immersion, respectively, reach 99.85%, 14.1 ± .4 GPa, and 77.8% at 1064-nm wavelengths after spark plasma sintering. These results are markedly superior to those of the ceramics prepared using the two other modes (97.43%, 6.8 ± .7 GPa, and 17.2% at 1064-nm wavelengths and 98.97%, 10.2 ± .5 GPa, and 47.8% at 1064-nm wavelengths, correspondingly). Therefore, water washing–ethanol immersion is a sensible and advisable treatment mode of precipitates for preparing YAG nanopowder and ceramics via coprecipitation.

Polymer–Salt Synthesis of Yb:YAG Nanopowders and Study of Their Structure and Luminescent Properties

Polymer–Salt Synthesis of Yb:YAG Nanopowders and Study of Their Structure and Luminescent Properties

Synthesis of yttrium aluminum garnet (Y3Al5O12, YAG) powder with nano and submicro size and high infrared transmittance using flame aerosol synthesis method

In this study, the flame aerosol synthesis (FAS) method was used to synthesize a yttrium aluminum garnet (Y3Al5O12, YAG) nanopowder. The dominant reaction route in the FAS method is the liquid route; this shaped the primary morphology of the YAG nanopowder into hollow and solid spheres. The effects of precursor concentration and annealing parameters were systematically investigated. At a precursor concentration of 0.4 mol L−1 and an annealing temperature of 1400 °C, the YAG nanopowder exhibited excellent infrared transmittance. Compared to other conventional synthesis methods, the FAS method has the advantages of high yield, low cost, and ease of obtaining a nanosized powder. The FAS method is thought to be one of the best choices for the large-scale production of YAG powders.

Laser induced broadband Vis and NIR emission from Yb:YAG nanopowders

The laser induced broadband emission (LIBE) of (YbxY1−x)3Al5O12 nanocrystals was investigated in vacuum using the focused infrared laser beam. The samples were prepared via Pechini's technique. The different shapes of LIBE spectra were observed. The LIBE characteristics including an order of the process, rise and decay times, were independent on the type of emission spectra and concentration of Yb3+ ions. Intensity of the emission spectra decreased/increased with time after switching off/on the laser excitation, while the shape of the emission spectra remained approximately the same. This is consistent with the colour of the emission, which remains white even after significant decrease in intensity. For the first time, the generation of broadband emission begins after reaching a certain “time threshold” in range 0–10 s, and disappearing afterwards. Beforehand, several possible LIBE mechanisms have been proposed for different materials, however they don’t cover all aspects of this phenomenon. In the present article, the intervalence charge transfer (IVCT) model is considered as general for RE doped phosphors. The features of LIBE have been described within this model.

Oxidation resistance, residual strength, and microstructural evolution in Al2O3-MgO–C refractory composites with YAG nanopowder

The decisive role of nanostructured yttrium aluminium garnet (YAG;Y3Al5O12) powder addition on oxidation resistance, residual strength and microstructural evolution were studied in Al2O3-MgO–C refractory composites. Oxidation index and rate constant calculations indicated that the oxidation resistance was almost 70 % improved for the nano-YAG containing refractories oxidized in air at 1600 °C. Residual compressive strength (Rc) estimations showed that there was nearly 75 % strength retained in these oxidized refractories fortified with nano-YAG. Residual bending strength (Rb) estimations based on cyclic thermal shock, exhibited that there was almost 70 % thermal shock resistance enhancement in refractories reinforced with nano-YAG, showed a good agreement between Rb and Rc values. These beneficial properties were attributed to the formation of a well-sintered framework of YAG/Spinel bonding grains throughout the dense oxidized layer microstructure of these new class of refractories. The concept of interfacial toughening and implications of these results to practical applications are discussed.

Полимерно-солевой синтез нанопорошков Yb:YAG и исследование их структуры и люминесцентных свойств

Experimental results of polymer-salt synthesis of Yb:YAG nanopowders and analysis of their structure and luminescent properties are presented. Infrared absorption spectra of synthesized materials are presented. The results of XRD analysis show that Yb:YAG nanocrystals with sizes of 18-35 nm form at a temperature of 900-1100 °С. The study on photoluminescence spectra and decay curves shows that properties of synthesized powders are close to properties of macroscopic materials produced by traditional high-temperature methods.

Optimizing co-precipitated Nd:YAG nanopowders for transparent ceramics

Nd:YAG transparent ceramics were obtained by vacuum sintering from nanopowders synthesized by co-precipitation method. The co-precipitated powder was optimized by studying calcination temperature (from 800 to 1300 °C) of the precursor and ball-milling time (from 0 to 24 h). Influences of calcination temperature and ball-milling time on comprehensive properties of nanopowders were studied in detail. Influences of sintering conditions (sintering temperature and holding time) on transmittance and microstructure were also investigated. The conclusions based on a comprehensive study of the whole ceramics processing from the powders synthesis to Nd:YAG ceramics sintering. The co-precipitated powder calcined at 1250 °C with ball-milling for 12 h demonstrates relatively better comprehensive properties. The 1.0 at% Nd:YAG ceramic sample with the thickness of 1.3 mm sintered at 1775 °C for 20 h has the highest in-line transmittance of 76.0% at 1064 nm. • Nd:YAG transparent ceramics were fabricated by vacuum sintering of co-precipitated nanopowders. • Influences of calcination temperature and ball-milling time on properties of Nd:YAG nanopowders were studied. • Influences of sintering conditions on transmittance and microstructure Nd:YAG ceramics were investigated.

Influence of ammonium sulfate on YAG nanopowders and Yb:YAG ceramics synthesized by a novel homogeneous co-precipitation method

Homogeneous and dispersed Y3Al5O12 (yttrium aluminum garnet, YAG) nanopowders were synthesized via a homogeneous co-precipitation method from the mixed solutions of yttrium nitrate, aluminum nitrate and a small amount of ammonium sulfate using hot urea as the precipitant. The method has the superiorities that co-precipitation of cations is ensured and continuous decomposition of the hot urea is achieved to obtain the narrow size distribution particles. The addition of small amount of ammonium sulfate surfactant, although has no influence on YAG garnet phase formation, has significant effect on dispersion, particles distribution and sinterability of the resultant YAG and Yb:YAG powders. Compared with the undoped sample, the green body of Yb:YAG doped with ammonium sulfate has higher total shrinkage, linear shrinkage rate and relative density through sintering at 1600 °C. The resultant Yb:YAG powders can be sintered into transparent ceramics at 1700 °C through vacuum sintering. The influence of the sulfate ions on characteristics of the resultant powders was thoroughly studied.

Effect of ammonium carbonate to metal ions molar ratio on synthesis and sintering of Nd:YAG nanopowders

Using the nanopowders synthesized by a reverse co-precipitation method, neodymium doped yttrium aluminum garnet (Nd:YAG) transparent ceramics were fabricated by vacuum sintering method. The influence of ammonium carbonate to metal ions (NH4HCO3/M3+) molar ratio (R value) on the properties of Nd:YAG precursors and powders, as well as the densification, microstructure, and transmittance of the resultant ceramics was systematically investigated. The results show that the precursors have similar compositions and the calcined powders have pure Y3Al5O12 (YAG) phase. However, the R value is closely related to the morphologies of the precursors and powders. It is found that the powder with R = 3.0 has strongest agglomeration and the powders with R = 3.2–4.0 show better dispersity. Using these powders as starting materials, the corresponding ceramics were sintered at 1720 °C for 20 h in vacuum. As a result, the ceramic with R = 3.2 obtains the best transmittance of about 72% at the wavelength of 1064 nm. The grain growth exponent and activation energy of the Nd:YAG ceramics fabricated from the powder with R = 3.2 were also studied.

Non-Calcined Nd:YAG Nanopowders Sintering to Transparent Ceramic

Non-Calcined Nd:YAG Nanopowders Sintering to Transparent Ceramic

High efficiency synthesis of Nd:YAG powder by a spray co-precipitation method for transparent ceramics

A spray co-precipitation method was developed to efficiently synthesize Nd:YAG nano-powders. The effects of spray speeds and solution concentrations on the crystallization processes of calcined precursors have been studied. The results indicated that the pure phase of YAG could be obtained by three different crystallization processes owing to different homogeneity levels of Y and Al mixing. Pure YAG powder was obtained at 850 °C and the phase purity persisted to 1600 °C. Using the obtained powders, transparent ceramics with the in-line transmittance up to 80.2%@400 nm and 83.1%@1064 nm were fabricated by gel-casting method and hot isostatic pressing sintering. Furthermore, the microstructure and laser properties of the transparent ceramics have been measured. The maximum laser output of 7.015 W has been obtained with an oscillation threshold and a slope efficiency of 0.235 W and 59.4%, respectively.

Synthesis of high quality Ce:YAG nanopowders by graphene oxide nanosheet-assisted co-precipitation method

(Ce0.04Y2.96)Al5O12 phosphor nanoparticles were prepared by a modified co-precipitation method with graphene oxide (GO) nanosheets used as dispersing agent. The GO concentration is controlled at 0, 0.005, 0.01, 0.02, and 0.03 g/L. The addition of lamellar GO nanosheets in the precipitant solution possibly enhances both the dispersity of precursor particles and the crystallinity of phosphor nanoparticles. Pure Ce-doped YAG phase is obtained by calcining the precipitate at 1000 °C for 3 h. The (Ce0.04Y2.96)Al5O12 phosphor nanoparticles have an average size of 64 nm and there is no significant change on particle size with increase of the GO concentration in precipitant solution. The luminescence property of (Ce0.04Y2.96)Al5O12 phosphor nanoparticles varies with different concentrations of GO. The photoluminescence emission intensity of the optimum sample with 0.02 g/L GO is about 1.6 times higher than the sample without using GO.

The effects of pH and excess Al3+ content on the microstructure and phase evolution of YAG polycrystals

Abstract YAG precursors were synthesized via a surfactant-free co-precipitation method using ammonium hydrogen carbonate as precipitant. The effect of final pH on Y/Al molar ratio was investigated. Moreover, the effects of excess aluminum ion content on the phase evolution and characteristics of YAG powders synthesized at pH value of 8 were explored. The chemical composition of the precursor, the phase transformation process and the characterization of the products were investigated by means of ICP, XRD, FTIR, TG-DTA, BET, FESEM, TEM and EDX analysis. The results showed that relatively high Y/Al ratio reduced the kinetics of YAG transformation and decreased homogeneity of the precursor while low Y/Al ratio did not alter the process features. Pure YAG nanopowders with particles mean diameter of 45 nm were obtained by calcination at 1000 °C for 2 h, with the addition of 15% mole of the excess aluminum source at pH value of 8.

Post-treatment of nanopowders-derived Nd:YAG transparent ceramics by hot isostatic pressing

Abstract Neodymium doped yttrium aluminum garnet (Nd:YAG) transparent ceramics were fabricated from Nd:YAG nanopowders synthesized via a reverse precipitation method by vacuum sintering and successive hot isostatic pressing (HIP) post-treatment. The powders obtained by calcining the precursor at 1100 °C for 4 h and then ball milling for 2 h with 0.5 wt% TEOS as sintering aid were used to fabricate Nd:YAG ceramics. The green bodies were vacuum sintered at 1500–1800 °C for 10 h, followed by the HIP at 1600 °C for 3 h in 200 MPa Ar atmosphere. Influence of the calcination temperature on the phase, morphology and particle size evolution of the nanopowders, as well as the optical transparency and microstructure of the obtained Nd:YAG ceramics before and after the HIP post-treatment was investigated in detail. It was found that for the post-treated 1800 °C-vacuum-sintered Nd:YAG ceramic sample, the in-line transmittance increased from 48.0% up to 81.2% at the lasing wavelength of 1064 nm.

Synthesis of yttrium aluminum garnet nanoparticles in confined environment, and their characterization

Nanopowders of yttrium aluminum garnet (YAG, Y3Al5O12) have been prepared by thermal treatment of hydroxides obtained by synthesis in a confined environment constituted by water/Cetyltrimethylammonium bromide (CTAB)/1-butanol/n-heptane.The phase behavior of the above system has been investigated on varying the water/CTAB molar ratio (R) at constant 1-butanol/CTAB and heptane/CTAB molar ratio. The dispersed aqueous phases were constituted by solutions of ammonia and of yttrium and aluminum nitrates, respectively. Measures of Kinematic Viscosity, Electrical Conductivity and Small Angle X-ray Scattering have been carried out. It was found that, on increasing the ammonia solution content the system evolves from a water in oil microemulsion to a bicontinuous one to a lamellar system and then it return to be bicontinuous, the yttrium and aluminum nitrate solution stabilizes the bicontinuous phase preventing the formation of the lamellar phase.The precursor synthesis was performed by mixing two microemulsions containing reactants at the same R, 20 and 70, respectively. The YAG nanopowders obtained from precursor calcination have been characterized by means of Wide Angle X-ray Scattering and Transmission Electron Microscopy.The obtained nanopowders were constituted by nanoparticles showing strong differences in terms of size and aggregation that depend on the microemulsion structure.

Low temperature synthesis and characterization of YAG nanopowders by polyacrylamide gel method

Yttrium aluminum garnet (YAG, Y3Al5O12)nanopowders were synthesized by a polyacrylamide gel method at a much lower temperature of 900°C than using the traditional methods. This synthesis process was thoroughly investigated including an examination of the phase transformation, the particle size and agglomeration degree at different molar ratios of monomer to the precursor salt and the calcination temperature. A high mole ratio of monomer to the precursor salt led to low formation temperature of YAG, resulting from the high homogeneity and reduced particle size of the precursor. Consequently, weak-agglomerated YAG nanopowder with an average particle size of 35nm can be prepared at a calcination temperature of 900°C for 2h. The as-prepared YAG nanopowder showed excellent sinter-ability.