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1.
A new concept of the structure of yttrium-aluminum garnet (Y 3Al 5O 12) has demonstrated the possibility of forming inversion twins in the (111) plane. The twinning processes are shown to be responsible
for stress relaxation during the growth and plastic deformation of Y 3Al 5O 12 single crystals. This way of stress relaxation can be used to describe the plastic deformation of other crystals, at least
cubic ones. 相似文献
2.
The immiscibility boundary and the critical point of SiO 2-Nd 2O 3 system glass were determined as a function of Al 2O 3 addition. The critical temperature of the immiscibility boundary was observed to decrease with the addition of Al 2O 3. Using the regular solution model, the observed decrease of the immiscibility boundary was directly related to the decrease of the concentration fluctuation of Nd 2O 3 in SiO 2. It is concluded that the Al 2O 3 addition to Nd 2O 3 containing silica glass is beneficial in decreasing the concentration quenching effect, deterioration of the optical efficiency due to clustering of rare earth element, because Al 2O 3 addition diminishes the concentration fluctuation of Nd 2O 3 in silica glass. 相似文献
3.
The phase separation and crystallization behavior in the system (80 − X)SiO 2 · X(Al 2O 3 + P 2O 5) · 5B 2O 3 · 15Na 2O (mol%) glasses was investigated. Glasses with X = 20 and 30 phase separated into two phases, one of which is rich in Al 2O 3-P 2O 5-SiO 2 and forms a continuous phase. Glasses containing a larger amount of Al 2O 3-P 2O 5 ( X = 40 and 50) readily crystallize and precipitates tridymite type AlPO 4 crystals. It is estimated that the phase separation occurs forming continuous Al 2O 3-P 2O 5-SiO 2 phase at first, and then tridymite type AlPO 4 crystals precipitate and grow in this phase. Highly transparent glass-ceramics comparable to glass can be successfully obtained by controlling heat treatment precisely. The crystal size and percent crystallinity of these transparent glass-ceramics are 20-30 nm and about 50%, respectively. 相似文献
4.
A new concept of the role of twinning in processes of plastic deformation is proposed which suggests mechanical twinning to be the main mechanism of solid-state reactions under the deformation mixing of components, in particular, the grinding of aluminum oxide (Al 2O 3) and yttrium oxide (Y 2O 3) powders, as a result of which yttrium-aluminum garnet (Y 3Al 5O 12) particles are formed. 相似文献
5.
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
6.
By rapid quenching in a twin roller apparatus, glass was found to occur widely in the systems of Li 2O with Al 2O 3, Ga 2O 3, Bi 2O 3 and in mixed systems. Examination of the resulting flakes by X-ray powder diffraction, differential thermal analysis, and capacitance data revealed the occurrence of glass, glass transitions, crystallization exotherms and the nature of some of the crystallization paths.The log ionic conductivity of the glasses was found to follow a linear relationship with the Li concentration. Evidence was observed for three new metastable crystalline phases, one in the Li 2OAl 2O 3 system and two in the Li 2OBi 2O 3 system. The latter system also showed evidence for the occurrence of two glasses at almost all compositions. 相似文献
7.
Single crystals of rare earth (RE) selenates of the compositions Nd(HSeO 4) 3, Sm(HSeO 4) 3, and Nd 2(SeO 4) 3 · 5H 2O are synthesized and studied by X-ray diffraction analysis at T = 297 and 180 K. It is established that Nd and Sm hydrogen selenates are isostructural to one another and to the corresponding
hydrogen sulfates. Neodymium selenate pentahydrate is not isostructural to the analogous RE sulfates, although their structural
motifs are similar.
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Translated from Kristallografiya, Vol. 49, No. 5, 2004, pp. 835–840.
Original Russian Text Copyright ? 2004 by Zakharov, Troyanov, Kemnitz. 相似文献
8.
The vitrification and crystallization behavior of melts produced at 1400 °C in the ternary system of K 2O-B 2O 3-TiO 2 is investigated. It is shown that there are two fields of compositions (indicated in mol%) which allow obtaining the glass-ceramic materials with continuous glassy matrix after the cooling of molten compositions. In the first field [TiO 2] = 25-57, [K 2O] = 30-50 and [B 2O 3] = 0-25, the glass-ceramics consisted of the potassium-titanium-borate glassy phase and different crystalline potassium titanates (K 4Ti 3O 8, K 2Ti 2O 5, K 2Ti 4O 9, K 2Ti 6O 13). The ratio of TiO 2:K 2O in the obtained titanates increases with [TiO 2] and [B 2O 3]. In the second field, [TiO 2] = 7-37, [K 2O] = 0-25 and [B 2O 3] = 52-93, the obtained glass-ceramics consisted of a similar vitreous phase, as mentioned above, and TiO 2 crystals. During the cooling of the melts, short whiskers-like crystals of anatase formed in the compositions with relatively low [TiO 2] and relatively high [K 2O], whereas long fiber-shaped crystals of rutile appeared with the compositions characterized with relatively high [TiO 2] and relatively low [K 2O]. The possible application of the obtained glass-ceramic materials as a source of fibrous TiO 2, for composite reinforcement, and as solid lubricants is discussed. 相似文献
9.
For the synthesis of ceramics and single crystals of yttriumaluminium garnet, a batch consisting of Y 2O 3 and Al 2O 3 is first treated thermally in order to obtain the garnet phase Y 3Al 5O 12. It is possible to make a choice of the optimum technological parameters of the batch if the amounts of all oxide phases, present during the synthesis, are well known. A combined X-ray quantitative method is suggested for this purpose. The initial oxides and a garnet phase are determined by the method with external standard. The rest two impurity oxide phases are determined as binary system. The specific diffraction characteristics of the present compounds were taken into account. The amounts of all phases in the batch, treated thermally from 1373 to 2075 K at every 100 K are shown. 相似文献
10.
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
11.
SiO 2-BaO-ZnO-xB 2O 3-(10−x) Y 2O 3, (0 ≤ x ≤ 10) glasses are synthesized. The effect of Y 2O 3 on the structural and optical properties of glasses has been investigated using different characterization techniques. The results are discussed in light of non-bridging oxygens (NBO), optical basicity and heat-treatment of glasses. The band gap has been calculated for as cast and heat-treated glasses. The band gap energy is found to decrease with the increasing content of Y 2O 3 in the glasses and heat-treatment. The presence of the crystalline phase in the glass matrix showed remarkable effect on band gap which decreases to semiconducting range. 相似文献
12.
Y 3Al 5O 12, yttrium aluminum garnet (YAG) single crystals are extensively used as host materials for solid‐state lasers. The materials in nano sizes are of immense importance due to their fascinating physical and chemical properties. Nanocrystals of Nd doped YAG were synthesized by low temperature glycol route. This method consists of a mixing of nitrates in an aqueous media at reasonably low temperatures. The Nd doping concentration was optimized and kept at 2 mol%. The prepared material was annealed at different temperatures. Single phase Nd:YAG nanocrystals were obtained at 850 °C. The prepared nanocrystals were characterized by XRD, SEM and TEM techniques for the crystalline phase, crystalline size and structure. The crystalline sizes were obtained in the range of ∼20–30 nm. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
Glasses in the Al 2O 3-SiO 2 and Nd 2O 3-Al 2O 3-SiO 2 systems were prepared by the sol-gel method. The gel-glass evolution was studied using near-infrared (NIR) and ultraviolet-visible (UV-VIS) spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). The results obtained indicate a relationship between the sample compositions, the treatment temperature and the Al coordination. In the samples of the Nd 2O 3-Al 2O 3-SiO 2 system the densification of the structure, when the treatment temperature increases, leads to the segregation of neodymium oxide particles. 相似文献
14.
Diffusion coefficients of various polyvalent ions (Sn 2+, As 3+, As 5+, Sb 3+, Sb 5+, Cr 3+, Ti 4+, V 4+, V 5+ and Fe 3+) were measured in melts with the basic compositions of 10CaO·10 BaO·10Al 2O 3·70SiO 2 and 10CaO·10BaO·15Al 2O 3·65SiO 2 by means of square-wave voltammetry. At temperatures in the range of 1300-1600 °C, linear correlations between log D and 1/ T were observed. At 1400 °C, the diffusion coefficients obtained are compared with those obtained from other glass melt compositions. 相似文献
15.
The atomic layer chemical vapor deposition (ALCVD) deposited Al 2O 3 and ZrO 2 films were investigated by ex situ X-ray photoelectron spectroscopy. The thickness dependence of band gap and valence band alignment was determined for these two dielectric layers. For layers thicker than 0.9 nm (Al 2O 3) or 0.6 nm (ZrO 2), the band gaps of the Al 2O 3 and ZrO 2 films deposited by ALCVD are 6.7±0.2 and 5.6±0.2 eV, respectively. The valence band offsets at the Al 2O 3/Si and ZrO 2/Si interface are determined to be 2.9±0.2 and 2.5±0.2 eV, respectively. Finally, the escape depths of Al 2p in Al 2O 3 and Zr 3p3 in ZrO 2 are 2.7 and 2.0 nm, respectively. 相似文献
16.
Conditions for the flux synthesis of Pb 3Ga 2Ge 4O 14 and Ba 3Ga 2Ge 4O 14 single crystals and their solid solutions Pb 3 − x
Ba xGa 2Ge 4O 14 are studied. Structural analysis showed that the Ga 3+-and Ge 4+-cation positions in flux-grown Pb 3Ga 2Ge 4O 14 and Ba 3Ga 2Ge 4O 14 single crystals are not mixed.
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Translated from Kristallografiya, Vol. 49, No. 2, 2004, pp. 325–328.
Original Russian Text Copyright ? 2004 by Bezmaternykh, Vasil’ev, Gudim, Temerov.
This work was presented at the National Conference on Crystal Growth (NCCG-2002, Moscow). 相似文献
17.
Ta 2O 5, Ta-Nb-O, Zr-Al-Nb-O, and Zr-Al-O mixture films or solid solutions were grown on Si(1 0 0) substrates at 300 °C by atomic layer deposition. The equivalent oxide thickness of Ta 2O 5 based capacitors was between 1 and 3 nm. In Zr-Al-O films, the high permittivity of ZrO 2 was combined with high resistivity of Al 2O 3 layers. The permittivity, surface roughness and interface charge density increased with the Zr content and the equivalent oxide thickness was between 2.0 and 2.5 nm. In the Zr-Al-Nb-O films the equivalent oxide thickness remained at 1.8-2.0 nm. 相似文献
18.
The crystallization conditions for the NaH 2PO 4, NaH 2PO 4 · H 2O, and NaH 2PO 4 · 2H 2O solid phases have been established from the analysis of the phase diagram of solubility of the ternary Na 2O-P 2O 5-H 2O system in the temperature range from 0 to 100°C. Based on these data, the methods for growing sodium dihydrogenphosphate
single crystals of the above compositions are developed. The initial components for preparing mother solutions were H 3PO 4 and NaOH solutions taken in certain weight ratios. For the first time, NaDP, NaDP · H 2O, and NaDP · 2H 2O single crystals were grown on a seed by the method of temperature decrease. The habits of the NaDP and NaDP · H 2O single crystals are determined.
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Translated from Kristallografiya, Vol. 47, No. 5, 2002, pp. 937–944.
Original Russian Text Copyright ? 2002 by Soboleva, Voloshin. 相似文献
19.
Neodymium (Nd) doped lutetium gallium garnet (Nd:Lu 3Ga 5O 12, Nd:LuGG) single crystal was successfully grown by the optical floating-zone method for the first time to our knowledge. Its absorption and luminescence spectra at room temperature were measured. By using the J–O theory, the spectral parameters of Nd:LuGG were calculated, which indicated that Nd:LuGG should possess comparable and even better laser properties than Nd:YAG. The maximum output power of 855 mW at 1062 nm was achieved with slope efficiency of 23.4% under a pump power of 5.2 W, and optical conversion efficiency of 16.4%. All the results show that Nd:LuGG is a potential laser material. 相似文献
20.
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
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