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141.
Abstract High-pressure studies of electroluminescence and photoconductivity are commonly carried out using liquid pressure systems. The wider application of a gas pressure system (with its substantial advantages) in this kind of studies is limited by the difficulties in the construction of a suitable sample cell. Such a cell, in addition to electric and optical access, must be provided with a high-pressure inlet, and the overall dimension of the cell should allow it to fit most standard cryostats. In this paper a high gas pressure optical cell is described which enables electroluminescence or photoconductivity measurements at pressures up to 1.0 GPa and at temperatures down to 1K. 相似文献
142.
K. Leinenweber J. Mosenfelder T. Diedrich E. Soignard T. G. Sharp J. A. Tyburczy 《高压研究》2013,33(3):283-292
A new series of high-pressure cells for in situ multi-anvil experiments is described. The cells are based on the conventional COMPRES cells, but modifications are made to improve the passage of X-rays. The modifications include cutting slits in parts of the assemblies that have very high X-ray absorption, such as lanthanum chromite and rhenium, the use of low-Z thermal insulation, such as forsterite, in place of zirconia, and the partial replacement of zirconia by MgO equatorial windows combined with a mullite octahedron. Details of the designs, thermal characterizations, and examples of the application of these cells are described. 相似文献
143.
采用微波等离子体化学气相沉积方法(microwave plasma chemical vapor deposition, MPCVD)在高沉积气压(34.5 kPa)下制备多晶金刚石,利用发射光谱(optical emission spectroscopy, OES)在线诊断了CH4/H2/O2等离子体内基团的谱线强度及其空间分布,并利用拉曼(Raman)光谱评价了不同O2体积分数下沉积出的金刚石膜质量,研究了金刚石膜质量的均匀性分布问题。结果表明:随着O2体积分数的增加,C2, CH及Hα基团的谱线强度均呈下降的趋势,而C2,CH与Hα谱线强度比值也随之下降,表明增加O2体积分数不仅导致等离子体中碳源基团的绝对浓度下降,而且碳源基团相对于氢原子的相对浓度也降低,使得金刚石的沉积速率下降而沉积质量提高。此外,具有刻蚀作用的OH基团的谱线强度却随着O2体积分数的增加而上升,这也有利于降低金刚石膜中非晶碳的含量。光谱空间诊断发现高沉积气压下等离子体内基团分布不均匀,特别是中心区域C2基团聚集造成该区域内非晶碳含量增加,最终导致金刚石膜质量分布的不均匀。 相似文献
144.
高压结晶PET/PC共混体系中生长在伸直链晶体内部球晶形态的观察 总被引:1,自引:1,他引:0
自从Wundedich等报道聚乙烯(PE)在高压结晶时可以生成伸直链晶体以来,相继很多有关聚合物体系的高压结晶行为方面的研究已见报道.研究结果表明,聚合物在高压下经历相转变时可产生非常丰富的微观结构,而球晶及伸直链晶体是其中最常见的两种结晶形态.但是,所观察到的这两种聚合物晶体都是分别存在,且独立生长的.到目前为止,尚未见到关于高压下球晶可以在伸直链晶体内部存在的报道. 相似文献
145.
In this contribution, photoluminescence and time-resolved photoluminescence spectra of Ca(NbO3)2 doped with Pr3+ obtained at high hydrostatic pressure up to 72 kbar applied in a diamond anvil cell are presented. At ambient conditions, the emission spectrum obtained in the time interval 0-1 μs is dominated by spin-allowed transitions from the 3P0 state. On the other hand, transitions from 1D2, characterized by a decay time equal to 30 μs dominate the steady-state luminescence.At pressures lower than 60 kbar, the continuous wave emission spectrum consists of sharp lines peaking between 600 and 625 nm, related to the 1D2→3H4 transition and three lines at 500, 550 and 650 nm related to emission transitions originating from the 3P0 level of Pr3+. The emission from the 1D2 excited state depends weakly on the pressure. Its decay time decreases from 33 μs at ambient pressure to less than 22 μs at 68 kbar. On the other hand, the 3P0 emission is strongly pressure dependent. At pressures of 60 kbar and higher, the Pr3+ emission intensity from the 3P0 state decreases. This is accompanied by a strong shortening of the luminescence decay time.The observed pressure quenching of the f-f emission transitions and the concomitant lifetime shortening have been attributed to increasing crossover from the 3P0 state of Pr3+ to a Pr3+-trapped exciton state. 相似文献
146.
A. Sacchetti T. Corridoni E. Arcangeletti P. Postorino 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):301-305
We report a high-pressure Raman study on two members of the La1-xCaxMnO3-δ manganite family (x = 0.20, δ = 0 and δ = 0.08). The results obtained for the δ = 0 sample show a different behavior in
the low and high pressure regime which is ascribed to the onset of a new pressure-activated interaction previously invoked
in other manganite compounds. The comparison of our results with literature data gives further support to the identification
of the Jahn-Teller sensitive stretching mode and shows that pressure-induced octahedral symmetrization is more effective in
systems exhibiting a lower metallic character. On the contrary the new interaction sets in at a pressure which decreases on
increasing the metallic character of the system indicating an important role of the Mn–Mn hopping integral in its activation. 相似文献
147.
A. Sacchetti M. Weller H. R. Ott Y. Ōnuki 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):307-313
We report a study of the low-temperature high-pressure phase diagram of the intermetallic compound PrCu2, by means of molecular-field calculations and 63,65Cu nuclear-quadrupole-resonance (NQR) measurements under pressure. The pressure-induced magnetically-ordered phase can be
accounted for by considering the influence of the crystal electric field on the 4f electron orbitals of the Pr3+ ions and by introducing a pressure-dependent exchange interaction between the corresponding local magnetic moments. Our experimental
data suggest that the order in the induced antiferromagnetic phase is incommensurate. The role of magnetic fluctuations both
at high and low pressures is also discussed. 相似文献
148.
K. Knorr L. Ehm M. Hytha B. Winkler W. Depmeier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):297-303
The high-pressure behaviour of PbS was investigated by angular dispersive X-ray powder diffraction up to pressures of 6.8
GPa. Experiments were accompanied by first principles calculations at the density functional theory level. By combining both
methods reliable data for the elastic properties of rock-salt type α- and high-pressure β-PbS could be obtained. β-PbS could be determined to crystallise in the CrB-type (B33), with space group Cmcm. The reversible ferro-elastic α/β transition is of first order. It is accompanied by a large volume discontinuity of about 5% and a coexistence region of the
two phases. A gliding mechanism of {001} bilayers along one of the cubic 〈110〉 directions governs the phase transition which can be described in terms of group/subgroup relationships via a common subgroup, despite its reconstructive character. The quadrupling of the primitive unit cell indicates a wave vector
(0, 0,π/
a
) on the Δ-line of the Brillouin zone.
Received 11 October 2002 Published online 14 February 2003
RID="a"
ID="a"Also at: Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 16253 Praha 6, Czech Republic e-mail: knorr@min.uni-kiel.de
RID="b"
ID="b"Present address: University of Cambridge, Cavendish Laboratory (TCM), Madingley Road, Cambridge CB3 0HE, UK
RID="c"
ID="c"Present address: Johann-Wolfgang Goethe Universit?t, Mineralogisches Institut, Kristallographie, Senckenberganlage 30, D 60054 Frankfurt a.M.,
Germany 相似文献
149.
G.G.N. Angilella F. Siringo R. Pucci 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):323-327
We argue that an ionic lattice surrounded by a Fermi liquid changes phase several times under pressure, oscillating between
the symmetric phase and a low-symmetry dimerized structure, as a consequence of Friedel oscillations in the pair potential.
Phase oscillations explain the tendency towards dimerization which has been recently reported for the light alkali metals
under high pressure. Moreover, a restoring of the symmetric phase is predicted for such elements at an even higher density.
Received 17 January 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: giuseppe.angilella@ct.infn.it 相似文献
150.
L. C. Li W. D. Xia H. L. Zhou Z. P. Zhou B. Bai 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):75-81
At atmospheric pressure, an intensified charge-coupled device (ICCD) camera
with a narrow-band filter is used to capture the unsaturated images of a
magnetically rotating arc. Comparison of its configurations with different
arc current and external axial magnetic field (AMF) strength shows that the
strong electromagnetic force may impel the arc to diffuse. Under the fully
diffuse mode, the plasma is distributed throughout the electrode gap and no
anode attachment can be seen in the cross-section of the torch. The fully
diffuse plasma runs more steadily and its intensity distribution is more
uniform, while its voltage fluctuation is reduced significantly.
Using a commercial CFD (computational fluid dynamics) code FLUENT, the fluid
flow and heat transfer of the fully diffuse plasma in an assumed magnetron
torch have been simulated for qualitatively discussing the AMF effects.
Numerical results show that the AMF significantly impels the plasma to
retract axially and expand radially. As a result, the plasma intensity
distribution on the cross section of the torch gets to be more uniform. 相似文献