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1.
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
2.
Doping possibilities of Al 2O 3 and YAG crystals grown from the melt alternatively doped with alkali earth, silicon, iron group or molybdenum ions under 98% Ar – 2% H 2 or 98% He – 2% H 2 protective atmosphere are described. Alkali earth and particularly Si ions evaporate slowly from the melt. Reduction of iron group ions was observed. Mo may enter YAG phase using a wet protective atmosphere. Al 2O 3 phase contains Mo ions if grown from the electrolyzed melt. 相似文献
3.
Ga 2O 3/SnO 2 coaxial nanowires were synthesized by thermal evaporation of GaN powders and then atomic layer deposition of SnO 2. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis results indicate that the Ga 2O 3 cores and the SnO 2 shells of the coaxial nanowires after thermal annealing are single crystals with monoclinic and simple orthorhombic structures, respectively, although the SnO 2 shells are amorphous before annealing. Our results also show that photoluminescence (PL) emission can be enhanced by thermal annealing in an H 2/N 2 atmosphere. EDX concentration profile suggests that the enhancement in the bluish green emission is due to the increase in the concentration of the Ga vacancies in the cores during the H 2/N 2 annealing. On the other hand, a red emission is newly formed while the bluish green emission is degraded by annealing in an oxygen or nitrogen atmosphere (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
The possibility of formation of molybdenum and tungsten polyoxides in the Mo–W–Al2O3–H2 system at T = 2400 K and P = 1 bar in a controlled Ar + H2 atmosphere has been investigated by the method of thermodynamic analysis. The formation of polyoxides is found to occur both due to the processes involving Al2O3 melt and in the absence of the latter. It is established that metals (Mo and W) and their mono-, di-, and even trioxides (in the latter case, mediated polymerization occurs) can be used as initial components to form polyoxides. It is shown that polyoxides themselves may interact with one of their main sources: Al2O3 melt. 相似文献
5.
The main chemical reactions between Mo and W polyoxides and Al2O3 melt in a controlled Ar + H2 atmosphere (T = 2400 K, P = 1 bar) during sapphire growth by horizontal directional solidification have been investigated. Under these thermodynamic conditions, the melt and products of its dissociative evaporation may actively react with the tungsten heater and molybdenum thermal screens of the crystallization system. It is shown that the polyoxides formed during evaporation do not directly interact with the melt; this interaction occurs only with participation of reagents exhibiting pronounced reducing properties (Al, H2, H, WO, Al2O, AlH, AlH2, AlH3). It is established that most of processes occur with participation of aluminum hydrides. A particular role of Mo(W) dioxide–W(Mo) polyoxide functional pairs in the interaction with the melt is determined. 相似文献
6.
Al 2O 3 and YAG crystals were purified from traces of iron by the growth in reducing atmosphere. Luminescence output of such materials was substantially increased, but some undesirable properties as transient colour centre formation in YAG: Nd and low damage threshol of ruby laser rods were observed. Minimum concentration of iron ions which drastically change spectral properties of oxide crystals seems to be ⪅ 10 −4 wt%. 相似文献
7.
Al 2O 3-Mo and Al 2O 3-W systems in a controlled Ar(95%) + H 2(5%) atmosphere at T = 2400 K and P = 1 bar have been calculated by the Monte Carlo method. It is established that the presence of hydrogen in these systems leads to the occurrence of OH, H 2O 2, HO 2, H 2O, AlOH, AlOOH, AlH, AlH 2, and AlH 3 components in the gas phase; aluminum hydrides are formed only through the interaction of hydrogen with melt evaporation products. The presence of reducing medium leads to a decrease in the free oxygen concentration by one to two orders of magnitude, which is expected to improve the quality of sapphire crystals. 相似文献
8.
Some gas phase processes during the vacuum vertical directed crystallization of α-Al 2 18O 3 are studied in this paper. An effect of these processes on the H, C, N concentrations in the crystals is discussed. The detected pulsations of partial H 2 and C 18O pressures are a result of bubble destruction at the melt-gas interface. The C 18O bubbles are formed because of chemical interaction between the melt and carbon-containing phases of container material. Besides the container wall, the H 2 bubbles can be generated also at the crystallization front supersaturated by H 2. The perfect α-Al 2O 3 and α-Al 2 18O 3 crystals grown under the same conditions have noticeable differences of their density, microhardness and lattice parameters. This is explained by an isotopic substitution effect. 相似文献
9.
Oxygen-containing germanium (Ge) single crystals with low density of grown-in dislocations were grown by the Czochralski (CZ) technique from a Ge melt, both with and without a covering by boron oxide (B 2O 3) liquid. Interstitially dissolved oxygen concentrations in the crystals were determined by the absorption peak at 855 cm −1 in the infrared absorption spectra at room temperature. It was found that oxygen concentration in a Ge crystal grown from melt partially or fully covered with B 2O 3 liquid was about 10 16 cm −3 and was almost the same as that in a Ge crystal grown without B 2O 3. Oxygen concentration in a Ge crystal was enhanced to be greater than 10 17 cm −3 by growing a crystal from a melt fully covered with B 2O 3; with the addition of germanium oxide powder, the maximum oxygen concentration achieved was 5.5×10 17 cm −3. The effective segregation coefficients of oxygen in the present Ge crystal growth were roughly estimated to be between 1.0 and 1.4. 相似文献
10.
Germanium (Ge) single crystals with an extremely low density of grown-in dislocations were grown by the Czochralski (CZ) technique with boron oxide (B 2O 3) liquid. Because attachment of particles floating on the melt surface to a growing Ge crystal leads to generation of dislocations during the growth, partial covering of the Ge melt surface with B 2O 3 liquid was attempted. Such attachment of particles was drastically suppressed or the particles were caught by the introduction of B 2O 3 liquid, and a particle-free Ge melt was realized in the central region of the melt surface. Ge single crystals were successfully grown from such melt, the grown-in dislocation density being 0–1×10 3 cm −2, which was remarkably lower than that in Ge crystals grown by a conventional CZ technique. The contaminations by B and O atoms of the grown crystal detected by SIMS analysis were very low. These Ge crystals have the potential for application to be applied as high-quality, dislocation-free substrates of GaAs solar cells for various usages including in space. 相似文献
11.
The changes in the main chemical reactions occurring upon the interaction between tungsten and the evaporation products of
Al 2O 3 melt are considered at a fixed temperature (2400 K). The concentrations of the components coexisting in equilibrium in a
closed system under isobaric-isothermal conditions are determined by stochastic simulation for low (× 10 −1−1 × 10 −3 bar) and high (1 × 10 −4 bar) vacuum. It is shown that the gas-liquid-solid system is in heterogeneous equilibrium for the basic component ratio W:
Al 2O 3 = 1: 1 in the entire pressure range under consideration. A detailed study of the chemistry of this system should facilitate
the choice of the optimal conditions for growing leucosapphire crystals from melt. 相似文献
12.
YAlO 3:Co (YAP:Co) single crystals have been obtained by the Czochralski method. The XPS spectra of YAP:Co annealed in reducing atmospheres: H 2, vacuum and vacuum plus H 2 are presented and discussed. As confirmed by magnetic measurements and the electron spectroscopy XPS the dopant concentration of Co is lower than a nominal one. The annealing processes removed colour centers due to relocation and some reduction of oxygen ions in the structure. The increased unit volume during the long annealing process may be caused by the change in some Co 3+ ions into Co 2+ ions. This explains the occurrence of the violet colour of the longtime annealed samples. The chemical shift analysis shows more ionic bond of Y–O than Al–O. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
Recharging processes of chromium ions were investigated for Mg 2SiO 4:Mg, Cr single crystals using annealing in O 2 and in air and γ‐irradiation, as compare to YAG :Ca, Cr single crystals. The formation of tetravalent Cr ions in the Mg 2SiO 4 :Mg, Cr is related not only to the initial Cr content in the melt, oxygen partial pressure and O 2‐ vacancy existing in the crystal, but also to the external field such as γ‐irradiation. The additional absorption after γ‐irradiation shows the decrease in intensity of the absorption of Cr 3+ and Cr 4+ ions in some part of the spectrum and increase in the other giving evidence on recharging effects between Cr 3+ and Cr 4+. There arises also color centers observed between 380 nm and 570 nm that may participate in energy transfer of any excitation to Cr 4+ giving rise to Cr 4+ emission. Opposite to forsterite crystal, absorption spectrum of YAG:Ca, Cr crystal after γ‐irradiation reveals only increase in the absorption of the Cr bands. The observed behavior of the absorption spectrum of YAG:Ca, Cr crystal under influence of γ‐irradiation suggests that γ‐irradiation ionizes only Cr ions. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
Hg 1−xCd xTe layers on CdTe substrates were grown from Te-rich melt solutions by a vertical dipping technique using a special quasi-closed system with ground-glass sealing. Results are good reproducibilities of the electrical properties after annealing in Hg-rich atmosphere ( p77 ≈ 2 · 10 16 cm −3 μ77 ≈ 500 cm 2 V −1 s −1) and of the x-value, respectively. A horizontal position of the substrate downwards to the melt solution yields, in difference to a vertical one, to homogeneous layer thicknesses. Short meltback steps before growth leads to sharper profiles of composition. 相似文献
15.
Fe and Fe 3O 4 thin films were grown by radio frequency magnetron sputtering. Fe 2O 3 was used as the target and hydrogen was introduced together with Argon gas to provide a certain reducing atmosphere. By varying H 2/Ar flow ratio, the changes in composition and structure of the thin films from (110) Fe to (111) Fe 3O 4 were observed by X-ray diffraction. The valence states of Fe in the thin films were analyzed by X-ray photoelectron spectroscopy. Magnetization measurements indicate that the Fe thin films grown with low H 2/Ar flow ratios possess large coercive force. It was ascribed to the increasing boundary density and the increasing amount of Fe oxides such as FeO distributed at the boundary. 相似文献
16.
(Ba, Sr)RuO 3 oxide electrodes have been studied for high dielectric (Ba, Sr)TiO 3 film in DRAM capacitors. Metal organic chemical vapor deposition (MOCVD) is used for large-scale deposition and provides better step coverage properties. In this work, methoxyethoxytetramethylheptanedionate (METHD) precursor and solvent [ n-butylacetate(C 6H 12O 2)] were mixed together into a single solution source. Post deposition annealing is carried out in oxygen atmosphere using rapid thermal annealing (RTA) to investigate the effect of organic impurities such as carbon during deposition. After annealing, resistivity of the BSR film decreased drastically compared to the as-deposited film. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis were used to describe this phenomenon accurately. The decrease in carbonate with increasing annealing time was confirmed by XRD analysis. 相似文献
17.
High-purity silica plates were implanted with 2 MeV Cu + ions at various ion fluences: 0.7 × 10 16, 3 × 10 16 and 6 × 10 16 ions/cm 2. After implantation, thermal treatments were performed at 400 °C and 900 °C in either an oxidizing (air) or a reducing (50% H 2 + 50% N 2) atmosphere for 1 h. All the samples were studied by electron paramagnetic resonance, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy (HRTEM), Rutherford backscattering spectrometry and optical absorption. The advantages of the reducing atmosphere (RA) over the oxidizing atmosphere (OA) are clearly observed. When annealed in a RA, the surface plasmon resonance is more intense and a narrower size distribution of the Cu nanoparticles is obtained. The existence of CuO nanoparticles was confirmed by HRTEM, and while both annealing atmospheres favor the formation of CuO nanoparticles, this process is strengthened when the sample is annealed in an OA. 相似文献
18.
Spectral properties of YAG and YAP grown in vacuum or under Ar H 2 protective atmosphere were compared. The latter contained small amounts of argon which was detected by a laser mass spectral analysis. Ar impurity evokes brown colour of unannealed crystals and strenghtens anomalous red colour of annealed (Particularly in O 2) YAP crystals doped with Nd + Cr or Nd + Mo. The same red coloration of the doped YAGs is less stable. 相似文献
19.
Thermodynamic parameters of melts (ΔH S, A 0, A 1) in the system Anorthite‐Diopside and Bi 2O 3‐Bi 4B 2O 9 have been calculated by a rigorous application of solution thermodynamics. The data are internally consistent and yield values of ΔH S for Anorthite = 133 kJ/mole, Diopside = 81 kJ/mole, Bi 2O 3 = 19 kJ/mole and Bi 4B 2O 9 = 39 kJ/mole. The activity of Anorthite and Diopside in an anorhtitic melt deviates negative from ideality, whereas a diopsidic melt behaves almost ideal. In a “Bi 2O 3” melt the activity of the Bi 2O 3 component is strongly positive, that of Bi 4B 2O 9 is strongly negative. The opposite is observed for the “Bi 4B 2O 9” melt. All calculated liquidi except the Bi 4B 2O 9 liquidus closely match the experimental ones. In contrast to the experimental liquidus the calculated Bi 4B 2O 9 liquidus has an inflection point. The crest of the metastable spinode (solvus) for a “Bi 2O 3” melt is close to the liquidus indicating melt separation at undercooling. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
Spectroscopic and laser properties of YAG:Nd and YAP:Nd grown from the nonstoichiometric melts or those containing Mo and Fe impurity were compared. YAG:Nd grown from the melt with surplus of Y 2O 3 and annealed in H 2 at ∼ 1400 °C have an increased laser performance. Mo admixture in hydrogen annealed YAP:Nd laser crystals suppresses effectively the detrimental action of iron impurity. 相似文献
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