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1.
Refractive indices of the nanocrystalline Y 3Al 5O 12 ceramic and a garnet single crystal of the same composition have been measured. In the visible and near IR range (0.4–1.064 μm), the prism method was used; in the medium IR range (2–6.2 μm), the interference method with the use of thin plates was applied. The refractive indices of these crystalline materials are practically the same over the entire spectral range studied and are described by the approximate formula proposed earlier for a single crystal. The parameters of the continuos-wave lasing in the nanocrystalline Y 3Al 5O 12 ceramic doped with Nd 3+ and Yb 3+ ions measured recently are presented. 相似文献
2.
Microhardness and fracture toughness of highly transparent Y 3Al 5O 12-and Y 3Al 5O 12: Nd 3+-based nanocrystalline ceramics are measured for the first time. For the Y 3Al 5O 12: Nd 3+ laser ceramics, the use of a longitudinal scheme with a diode-laser pumping at a wavelength of 1.3186 mm ( 4 F 3/2 → 4 I 13/2 channel) enabled one to attain an output power of continuous-wave lasing of ~3.7 W with 35% efficiency. 相似文献
3.
The influence of the size of Y2O3 powder particles on the structure formation and densification of Nd3+:Y3Al5O12 laser ceramics has been studied. It is shown that the use of 50- and 100-nm yttrium oxide particles makes it possible to synthesize single-phase yttrium aluminum garnet at temperatures of 1200 and 1500°C, respectively, whereas in the case of 5000-nm yttrium oxide particles 2-h exposure at a temperature of 1500°C yields only 80 wt % of the Nd3+:Y3Al5O12 phase. Bulk swelling of pressed samples during sintering of 2.94Y2O3-0.06Nd2O3-5Al2O3 powders with the size ratio of the initial particles R(Al2O3/Y2O3) ~ 5 is observed. The application of different-sized powders (R ~ 2.5) provides quantitative ratios between phases in the 3Y2O3-5Al2O3 system at which shrinkage in a temperature range of 20–1500°C is dominant. Laser ceramics 0–2 at % Nd3+:Y3Al5O12 have been obtained by the solid-phase sintering of oxide powders (R ~ 2.5). The slope efficiency for 1 at % Nd3+:Y3Al5O12 laser ceramics is found to be 33%. 相似文献
4.
The microhardness and fracture toughness of laser nanocrystalline ceramics based on the cubic oxides Y 2O 3 and Y 3Al 5O 12 are determined experimentally. It is shown by comparative measurements that the fracture toughness and microhardness of Y 2O 3 ceramics exceed the corresponding parameters of Y 2O 3 single crystals by factors of 2.5 and 1.3, respectively. The fine morphology of grains and grain boundaries in fractures is investigated. It is ascertained that changes in the mechanical properties of the nanocrystalline ceramics under study are related to both the sizes and structure of grains and the structure of grain boundaries. It is suggested that twinning processes determine the mechanisms of formation of nanocrystalline ceramics. 相似文献
5.
Transparent 0.1 at.%Cr,1.0 at.%Nd:YAG (Y 3Al 5O 12) ceramics were fabricated by a solid-state reaction and vacuum sintering with CaO as a charge compensator and tetraethyl orthosilicate (TEOS) as a sintering aid using high-purity powders of Al 2O 3, Y 2O 3, Nd 2O 3 and Cr 2O 3. The mixed powder compacts were sintered at 1800 °C for 5 h and 30 h under vacuum. The optical transmittance of the Cr,Nd:YAG ceramics sintered at 1800 °C for 5 h and 30 h is ∼63% and ∼78% in the infrared wavelengths, respectively. The two samples exhibit pore-free structures and the average grain size is about 10 and 20 μm. For the sample sintered at 1800 °C for 5 h, the dominant fracture mechanism is the transgranular fracture. With increase of holding time up to 30 h, the ratio of intergranular fracture surfaces increase and more Cr 3+ ions in the Cr,Nd:YAG ceramic transform to Cr 4+. High-quality Cr 4+,Nd 3+:YAG transparent ceramics may be a potential self-Q-switched laser material. 相似文献
6.
Silica submicron spherical particles coated with an yttrium aluminum garnet (Y 3Al 5O 12, YAG) layer doped with Eu 3+ were prepared by the sol–gel method. The structure and morphology of samples determined by the X-ray powder diffraction measurements and transmission electron microscope images, respectively, indicated that well-crystallized garnet nanocrystallites were formed with successive coating cycles. Similar trends were deduced from the evolution of the luminescence spectra. The ratio of integrated intensities of the 5D 0 → 7F 2 and 5D 0 → 7F 1 transitions was used to analyze the structural variations in the surroundings of the Eu 3+ ion. The effect of coating was analyzed by comparing the luminescence properties of the Y 3Al 5O 12:Eu 3+ nanocrystalline powders and composite Y 3Al 5O 12:Eu 3+/SiO 2 materials. 相似文献
7.
The utilization of liquid-phase epitaxy for growing thin yttrium-aluminium garnet films is discussed. By transfer method from lead solvents films were obtained with a composition Y 3Al 5O 12: Nd 3+ on substrates with composition Y 3Al 5O 12, and films Y 3Al 5O 12: Er 3+, Y 3Al 5O 12: Er 3+, Ga 3+ (about 40 wt% of erbium) on substrates Y 3Al 5O 12: Nd 3+ Characteristics are given for simultaneous induced emission generation of the system film-substrate at 77 K Er 3+ ion (λ gen = 1.6602 μ) being a component of the film, and Nd 3+ ion, being a component of the substrate (λ gen = 1.061 μm). The results obtained are discussed. 相似文献
8.
In order to find a new glass host and optimize erbium doping for IR glass optical amplifiers in photonic applications, a study on the optimization of the emission of erbium ions in the SiO 2–Al 2O 3 glass by codoping with Y 2O 3 is performed. It is first attempted to make a new sol–gel glass host based on SiO 2, Al 2O 3, and Y 2O 3 doped with Er 3+ ions of the composition (1− x)SiO 2– xAl 2O 3– yY 2O 3:0.65Er 2O 3 (in mol%), x varies from 0 to 65, and y from 0 to 4. The optimal proportion in mol% of SiO 2 and Al 2O 3 for the Er 3+ emission (at a fixed optimal concentration of 0.65) was 65 – 35. The effect of Y 2O 3 content on photoluminescence, decay curve profiles and lifetime of the 4I 13/2 level of Er 3+ in SiO 2–Al 2O 3 glass is observed. The largest quantum efficiency and the higher emission intensity are observed in the sample with 65Al 2O 3 and 4Y 2O 3. The emission intensity at 1530 nm is two times higher than in glasses without Y 2O 3. A shift of 3 nm to shorter wavelengths is observed. The emission spectral profiles are flatter and broader for the glasses containing Al and Y (bandwidth of 59.5 nm). The decay curves show strong difference profiles for the different samples. The increase of the lifetime value τ (about ms) of the 4I 13/2 level of Er 3+ in the SiO 2–Al 2O 3 with the Y 2O 3 is discussed. 相似文献
9.
The absorption spectra of the undoped Y 2SiO 5 and Eu 3+-doped Y 2SiO 5 crystals grown by the Czochralski technique were compared before and after annealing and, similarly, the unannealed and annealed crystals after γ-ray irradiation. The absorption bands of Eu 2+ ions with peaks at 300 and 390 nm were observed in the as-grown Y 2SiO 5:Eu 3+ crystal. These peaks were more intense in H 2-annealed and irradiated Y 2SiO 5:Eu 3+ crystals. The additional absorption peaks at 260 and 320-330 nm which were attributed to F color centers and O − hole centers were observed in irradiated undoped Y 2SiO 5 and Y 2SiO 5:Eu 3+ crystals, respectively. 相似文献
10.
The Pr 3+-doped Y 4Al 2O 9 powders were synthesized by sol–gel method. Powder X-ray diffraction and SEM techniques were used to check for Y 4Al 2O 9 powders. The Li + co-doping with Pr 3+ has an influence on the sintering temperature and morphology of the Y 4Al 2O 9 powders produced from the gel. The emission spectra under different excitations, e.g., the 488 nm line of an argon-ion laser, X-ray and UV light, were investigated. The luminescence intensity of Y 4Al 2O 9:Pr 3+ could be increased with Li + co-doping. Luminescence properties of Pr 3+ ions in the two samples have some difference. In the Y 4Al 2O 9:Pr 3+, the emission at 490 nm from 3P 0 is dominant, while, the Y 4Al 2O 9:(Pr 3+ + Li +) system was characterized by a red emission at 607 and 610 nm corresponding to the 1D 2 → 3H 4 inner transition of Pr 3+ ions; and these two emissions show different excitation band from the 4f5d state. 相似文献
11.
YAG crystals doped with 0.01 wt% Cr were grown by Czochralski method using 98% Ar + 2% H 2 protective atmosphere. Four colour varieties of the crystals were prepared in the dependence of the Al 2O 3 :Y 2O 3 ratio in the melt and the sign of electrical potential above the melt level. New absorption bands were attributed to the O − centre (400 to 480 nm), F centre (357, 500, and 833 nm) or Cr 3+ at another site than octahedral (455, and 612 nm). 相似文献
12.
Optically transparent garnet single crystals were grown from Lu 3Al 5O 12 melts containing different RE 3+ ions. The distribution coefficient of Nd 3+ ions is found to be a function of the growth rate. Lu 2O 3–Al 2O 3 system studies have been partially carried out. Measurements of the lattice data, absorption spectra and comparison with some properties of Y 3Al 5O 12 single crystals have also been made. 相似文献
13.
Garnet crystals of the composition Gd 3Ga 5O 12:Nd 3+ (concentration series C Nd = 1–10 at. %) were grown from flux. In terms of spectroscopy, these crystals, unlike those grown from melts, form medium with a single activator center. For the first time, continuous-wave lasing was excited by diode pumping with the use of Gd 3Ga 5O 12:Nd 3+ crystals at the wavelengths λ 3 = 1.3315 and λ 4 = 1.3370 μm of the 4F 3/2 → 4I 13/2 channel and also the simultaneous generation at two wavelengths, λ 1 = 1.0621 and λ 2 = 1.0600 μm, of the 4F 3/2 → 4I 11/2 channel. 相似文献
14.
The activation of Y 2O 3, Gd 2O 3and (Y 0.7,Gd 0.3) 2O 3 with Eu 3+ ions at temperatures lower than 1000 °C is studied using different starting compounds. The activator ions are introduced during the crystallization or precipitation of the precursor. Phosphors prepared from hydroxides and activated at 900 °C exhibit luminescence with high efficiency under 254 nm Hg-line excitation. Strong emission is observed even in samples activated at 700 °C. Luminescence intensity, emission and excitation spectra are compared to these of Y 2O 3:Eu produced by the industry. 相似文献
15.
CsI single crystals were grown from the melt scavenged by Y 3+ (YCl 3) addition in 6.7·10 −4–6.7·10 −3 mol·kg −1 range. The addition of the scavenger amounts comparable with the total concentration of the oxygen‐containing admixtures in molten CsI results in complete destruction of the latter. Because of this, the intensity of the band with a maximum at 2.8 eV in radioluminescence spectra caused by the oxygen‐containing admixtures (anion vacancies) considerably decreases, and the fraction of the slow 2μs‐component corresponding to these admixtures becomes lower than 0.01 (0.007). The addition of larger quantities of YCl 3 leads to the appearance of a wide band with a maximum at 2.8 eV caused by cation vacancies, and the intensity of the slow 2μs‐component increases to 0.02. The maximum ratio of two faster components with the decay constants equal to 7 and 30 ns reaches 0.65:0.33 at Y 3+ concentration in CsI melt equal to 6.7·10 ‐3 mol·kg ‐1, the effective luminescence time of fastest components is ca 14 ns. The dependence of the ‘Fast/Total ratio’ on Y 3+ concentration passes through its maximum (0.81) corresponding to the equivalence of Y 3+ and O 2− concentrations in the growth CsI melt. 相似文献
16.
Absorption and luminescent properties of a Pb 3Ga 2Ge 4O 14:Nd 3+ crystal have been studied. The refractive indices are measured in the range from 0.405 to 1.064 μm, and the molecular refraction is calculated. 相似文献
17.
Luminescence characteristics of Yb 3+, La 3+ codoped yttrium oxide nanopowders were investigated. The grain size and the crystallinity of (Yb 0.05Y 0.90La 0.05) 2O 3 nanopowders increase with the increase of calcination temperature. The average grain size of the nanopowders calcined at 1100 °C is 66 nm and its cooperative up-conversion luminescence centered at 498 nm was detected due to nanometer size effect and perfect crystallinity. However, the cooperative up-conversion luminescence of (Yb 0.05Y 0.90La 0.05) 2O 3 transparent ceramics was not detected. 相似文献
18.
The luminescence behavior of composite materials consisting of nanocrystals of Y 3?xAl 5O 12:Tb (YAG:Tb 3+) embedded into silica xerogel has been studied. Blue and green luminescence of the materials is due to a cross-relaxation effect in Tb 3+ ions doped into a YAG lattice. The materials with YAG:Tb 3+ nanocrystals immobilized in silica exhibit enhancement of Tb 3+ luminescence in comparison with the macrocrystalline YAG:Tb 3+ powder. The Tb 3+ luminescence intensity of a composite material dried at room temperature can be improved when higher aliphatic alcohols are applied in a one-pot procedure during a sol–gel synthesis. On the other hand, the Tb 3+ luminescence is quenched in the presence of Ag nanoparticles in the material. The composite material (YAG:Tb 3+ in silica) exhibits thermal stability at higher temperatures and achieves the highest emission intensity after having been annealed at 700 °C. 相似文献
19.
(Er,Yb):YAl 3(BO 3) 4 single crystals of optical quality, up to 15 × 10 × 10 mm 3 in size, have been grown from a (Er 0.023Yb 0.116Y 0.862)Al 3(BO 3) 4 solution in a Y 2O 3-B 2O 3-K 2Mo 3O 10 melt. The initial borate concentration was 17 wt %, and the flux cooling rate increased from 0.08 to 0.12°C/h in the range 1060–1000°C. The physical properties of the single crystals grown are good enough that they can be used as laser elements in systems with diode pumping and radiation near 1.5 μm. 相似文献
20.
Crystals of solid solutions (R xY 1-x) 3Al 5O 12 (where R is rare earth ion Er 3+, Yb 3+, Tb 3+, Ho 3+, Tm 3+) with garnet structure were grown. The temperature dependencies of magnetic susceptibility for these crystals were obtained. On the basis of measurement of magnetic susceptibility a non-destructive technique for determining the concentration of rare earth ions in yttrium-aluminum garnets was developed. 相似文献
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