首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 781 毫秒
1.
The solid solution ranges in the systems (Rb4?xKx)Cu16I7Cl13, (Rb4?xCsx)Cu16I7Cl13, Rb4Cu16(I7?xBrx)Cl13, and Rb4Cu16I7(Cl13?xBrx), have been examined and the electrical conductivity has been measured as a function of temperature and composition. In the system (Rb4?xKx)Cu16I7Cl13, room temperature conductivities increase from 0.32Scm?1 for x=0 to 0.47Scm?1 for x=0.40. On the other hand, the conductivities of the systems (Rb4?xCsx)Cu16I7Cl13 and Rb4Cu16I7(Cl13?xBrx) decrease with increasing x. The system Rb4Cu16(I7?xBrx)Cl13 shows no significant change of the conductivity on x.  相似文献   

2.
We report the room temperature spectroscopic ellipsometry study of Cu2ZnGeSe4 and Cu2ZnSiSe4 crystals, grown by modified Bridgman technique. Optical measurements were performed in the range 1.2–4.6 eV. The spectral dependence of the complex pseudodielectric functions as well as pseudo- complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity of Cu2ZnGeSe4 and Cu2ZnSiSe4 crystals were derived. The observed structures in the optical spectra were analyzed by Adachi's model and attributed to the band edge transitions and higher lying interband transitions. The parameters such as strength, threshold energy, and broadening, corresponding to the E0, E1A and E1B interband transitions, have been determined using the simulated annealing algorithm.  相似文献   

3.
Wf/Cu82Al10Fe4Ni4(30) composites and Wf/Cu82Al10Fe4Ni4(60) composites were prepared by penetrating casting method. Three-point bending test and dynamic compression test showed that Wf/Cu82Al10Fe4Ni4(30) composites possessed higher mechanical properties than Wf/Cu82Al10Fe4Ni4(60) composites. Microstructure observation of Wf/Cu82Al10Fe4Ni4(30) composites revealed that a small amount of tungsten diffused into the Fe–Ni solid solution precipitated on the surface of tungsten fibers. The damage occurred mainly within the tungsten fibers after three-point bending test and dynamic compression test in Wf/Cu82Al10Fe4Ni4(30) composites, indicating that the composites possessed high interface strength. Dislocation density was high and stacking faults emerged in Wf/Cu82Al10Fe4Ni4(30) composites after dynamic compression. Microstructure observation of Wf/Cu82Al10Fe4Ni4(60) composites revealed that long strip of tungsten grains occurred at the edge of tungsten fibers, within which damage mainly emerged after three-point bending test, indicating that strength of the edge of tungsten fibers was low in Wf/Cu82Al10Fe4Ni4(60) composites. The fibrous structure of tungsten fiber was coarse or even disappeared in some areas, and dislocation density was low in Wf/Cu82Al10Fe4Ni4(60) composites after dynamic compression.  相似文献   

4.
Tm3Cu4Sn4 has been studied by single - crystal X - ray diffraction analysis. The structure is of a new type with space group C2/m and Z = 2:a = 16.119(2), b = 4.3935(6), c = 6.896(1) A?, β = 115.88(2)°, Dx = 9.32 Mgm?3, μ(MoKα) = 52 mm?1, F(000) = 1045, R = 0.056 for 558 independant reflexions (Rw = 0.058). Tm3Cu4Sn4 is a monoclinic distorded variety of the Gd3Cu4Ge4 structure type. Seven other compounds were characterized: Sc3Cu4Ge4 and R. E3Cu4Sn4 where R.E. = Y, Gd, Tb, Dy, Ho, Er, isostructural with Gd3Cu4Sn4.  相似文献   

5.
Copper(II)metagermanate, CuGeO3, decomposes at high pressure to rutile-type GeO2 and Cu2GeO4. Very small single crystals of Cu2GeO4 can be obtained by direct high pressure synthesis from CuOGeO2 mixtures. The compound has a distorted spinel structure (Hausmannite structure, space group I41amd) with a = 5.593 A?, c = 9.396 A?, Z = 4.  相似文献   

6.
Multi-stage evaporation is a well-established method for the controlled growth of chalcopyrite thin films. To apply this technique to the deposition of Cu2ZnSnS4 thin films we investigated two different stage sequences: (A) using Cu2SnS3 as precursor to react with Zn-S and (B) using ZnS as precursor to react with Cu-Sn-S. Both Cu2SnS3 and ZnS are structurally related to Cu2ZnSnS4. In case (A) the formation of copper tin sulphide in the first stage was realized by depositing Mo/SnSx/CuS (1 < x < 2) and subsequent annealing. In the second stage ZnS was evaporated in excess at different substrate temperatures. We assign a significant drop of ZnS incorporation at elevated temperatures to a decrease of ZnS surface adhesion, which indicates a self-limited process with solely reactive adsorption of ZnS at high temperatures. In case (B) firstly ZnS was deposited at a substrate temperature of 150 °C. In the second stage Cu, Sn and S were evaporated simultaneously at varying substrate temperatures. At temperatures above 400 °C we find a strong decrease of Sn-incorporation and also a Zn-loss in the layers. The re-evaporation of elemental Zn has to be assumed. XRD measurements after KCN-etch on the layers prepared at 380 °C show for both sample types clearly kesterite, though an additional share of ZnS and Cu2SnS3 can not be excluded. SEM micrographs reveal that films of sample type B are denser and have larger crystallites than for sample type A, where the porous morphology of the tin sulphide precursor is still observable. Solar cells of these absorbers reached conversion efficiencies of 1.1% and open circuit voltages of up to 500 mV.  相似文献   

7.
Cu2MnTi3S8 and Cu2NiTi3S8 compounds were prepared by high-temperature synthesis. The crystal structure of these quaternary phases was investigated by X-ray powder diffraction. The compounds are described in the thiospinel structure (space group ) with the lattice constants a = 1.00353(1) nm (Cu2MnTi3S8) and a = 0.99716(1) nm (Cu2NiTi3S8). The atomic parameters were calculated in anisotropic approximation (RI = 0.0456 and RI = 0.0520 for Cu2MnTi3S8 and Cu2NiTi3S8, respectively).  相似文献   

8.
The Cu4SO4(OH)6 was synthesized by a simple hydrothermal reaction with a yield of ~ 90%. Using Cu4SO4(OH)6 as the starting material, novel fishbone-like Cu(OH)2 was produced by a direct reaction of Cu4SO4(OH)6 with NaOH solution. The Cu(OH)2 consists of many needle-like nanorods parallel to each other and perpendicular to the direction of backbone, forming fishbone-like structure. Using the fishbone-like Cu(OH)2 as the sacrificial precursor, CuO with similar size and morphology was obtained through a simple heat treatment. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, X-ray photoelectron spectroscopy, BET nitrogen adsorption, and UV-Vis absorption spectroscopy were employed to characterize the as-prepared samples. The conversion of the Cu4SO4(OH)6 to the fishbone-like Cu(OH)2 was visualized by time-dependent SEM images. A mechanism was also proposed based on the observed results.  相似文献   

9.
We report the existence of silver halide-rich glasses of a type not previously recognized. These contain only monovalent halides and represent perhaps the simplest ionic glasses yet realized. Despite the lack of the usual oxyanion matrix the new glasses show room temperature conductances which equal or exceed those of the best Ag+ glasses yet reported. Cu+ analogues have also been prepared. At the high conducting extreme apparently lies a vitreous state analog of the well-known crystalline conductor RbAg4I5. A crystalline analog of the latter FIC, CsAg4 (I0.45Cl0.55)5 forms metastably on careful devitrification of the glass. Like its prototype, it has a very high conductivity and exhibits a sharp Cp anomaly at low temperatures, ?77°C, in the vicinity of which the activation energy for conductance changes abruptly.  相似文献   

10.
The paper reports the effect of the addition of small amount of Al on the microstructure and properties of HITPERM class rapidly solidified Fe44Co44Zr7B4Cu1 glassy alloy. Using three dimensional atom probe measurements we present evidence for the formation of Cu clusters on annealing in the metallic glass matrix of the Al containing alloy Fe43Co43Al2Zr7B4Cu1. Such clusters are otherwise absent in the parent alloy under similar conditions. The Cu clusters provides heterogeneous nucleation sites for the formation of bcc α′-FeCo phase leading to an increase in number density of this nanocrystalline phase and thereby enhancing the magnetic properties.  相似文献   

11.
In this study we investigated the optical properties of Cu2ZnSnSe4 monograin powders that were synthesized from binary compounds in the liquid phase of flux material (KI) in evacuated quartz ampoules. The monograin powder had p-type conductivity. Radiative recombination processes in Cu2ZnSnSe4 monograins were studied using photoluminescence spectroscopy. The detected low-temperature (T = 10 K) photoluminescence band at 0.946 eV results from band-to-impurity recombination in Cu2ZnSnSe4. The ionization energy of the corresponding acceptor defect was found to be 69 ± 4 meV. Additional photoluminescence bands detected at 0.765 eV, 0.810 eV and 0.860 eV are proposed to result from Cu2SnSe3 phase whose presence in the as-grown monograins was detected by Raman spectroscopy and SEM analysis. Considering photoluminescence results, it is proposed that the optical bandgap energy of Cu2ZnSnSe4 is around 1.02 eV at 10 K.  相似文献   

12.
Synthesis and upconversion luminescence properties of the new BaGd2(MoO4)4:Yb3+,Er3+ phosphor were reported in this paper. The phosphor powder was obtained by the traditional high temperature solid-state method, and its phase structure was characterized by the XRD pattern. Based on the upconversion luminescence properties studies, it is found that, under 980 nm semiconductor laser excitation, BaGd2(MoO4)4:Yb3+,Er3+ phosphor exhibits intense green upconversion luminescence, which is ascribed to 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transition of Er3+. While the observed much weaker red emission is due to the non-radiative relaxation process of 4S3/2 → 4F9/2 and 4F9/2 → 4I15/2 transition originating from the same Er3+. The concentration quenching effects for both Yb3+ and Er3+ were found, and the optimum doping concentrations of 0.5 mol% Yb3+ and 0.08 mol% Er3+ in the new BaGd2(MoO4)4 Gd3+ host were established.  相似文献   

13.
The crystal structures of the new compounds Na2Cu4S3 and KCu3Te2 have been solved. Na2Cu4S3 crystallizes in the K2Ag4S3 structure (space group: C2/m, a = 1563(3) pm, b = 386(2) pm, c = 1033(2) pm, β = 107.6o, N = 4), KCu3Te2 in the CsAg3S2 structure (space group: C2/m, a = 1645.3(9) pm, b = 429.4(4) pm, c = 866.1(6) pm, β = 111.86o, N = 4).  相似文献   

14.
A general empirical formula was found for calculating lattice thermal expansion for compounds having their properties extended for compound groups having different mean ionicity as well as more than one type of cation atoms with that of different numbers of them such as I2-IV-VI3 and I3-V-VI4. The difference in the valence electrons for cations and anions in the compound was used to correlate the deviations caused by the compound ionicity. The ionicity effects, which are due to their different numbers for their types, were also added to the correlation equation. In general, the lattice thermal expansion for a compound semiconductor can be calculated from a relation containing melting point, mean atomic distance and number of valence electrons for the atoms forming the compound. The mean ionicity for the group compounds forming I2-IV-VI3 was found to be 0.323 and 0.785 for the ternary group compounds of I3-V-VI4.  相似文献   

15.
Cu2ZnSnSe4 thin films with different substrate temperature and Cu flux were grown by thermal co-evaporation. Raman scattering, photoluminescence, and contactless electroreflectance (ER) measurements were performed. The Raman spectra of Cu2ZnSnSe4 show two main peaks at 170 and 192 cm− 1. The photoluminescence spectrum shows a peak below 1.0 eV. Franz-Keldysh oscillations (FKOs) were observed in the ER spectra. From the analysis of the FKOs, the bandgap energy of Cu2ZnSnSe4 thin films is estimated to be 1.07 eV at 90 K and 0.99 eV at room temperature. We conclude that the bandgap energy of Cu2ZnSnSe4 thin films is around 1.0 eV.  相似文献   

16.
Cu2ZnSnS4 (CZTS) and Cu2FeSnS4 (CFTS) nanoparticles were synthesized by thermal decomposition of metal precursors. Dispersion of the precursors in the solvent prior to reaction significantly lowered the temperature and time required for the reaction. Extensive characterization of the synthesized nanoparticles was done. Materials characteristics of the synthesized nanoparticles such as elemental composition, band gap and morphology were found to be similar to the nanoparticles prepared by conventional synthesis techniques.  相似文献   

17.
Significant changes in the local atomic structure and lattice dynamics were observed by pulsed neutron inelastic scattering measurements on YBa2Cu4O8 both around the superconducting transition temperature and around the spin-gap temperature. These observations and earlier results of numerical calculations on the enhancement of electron-lattice interaction by electron correlation lead to a novel picture of unconventional lattice-induced superconductivity related to antiferroelectric instability.  相似文献   

18.
C. Tablero 《Thin solid films》2012,520(15):5011-5013
The optoelectronic properties of Cu2ZnSnS4 and environmental considerations have attracted significant interest for photovoltaics. Using first-principles, we analyze the possible improvement of this material as a photovoltaic absorber via the isoelectronic substitution of S with O atoms. The evolution of the acceptor level is analyzed with respect to the atomic position of the nearest neighbors of the O atom. We estimate the maximum efficiency of this compound when used as a light absorber. The presence of the sub-band gap level below the conduction band could increases the solar-energy conversion with respect to the host.  相似文献   

19.
Ternary (Cu2TlX2) and quarternary (Cu3YTl2X4) compounds (with X = Se, Te and Y = Fe, Ga, Al) have been prepared and characterized. All of them have the same lamellar structure where tetrahedras (CuYX4)n and thallium atoms in coordination eight form successive layers. Some are metallic conductors (Cu2TlX2) whereas others are semi-conductors (Cu3YTlX4). The metallic behaviour could be due to thallium monovalent-thallium trivalent interactions within the layers.  相似文献   

20.
Presence of various nano-scale Y2Ba4CuMOy phase inclusions in YBa2Cu3O7−δ phase matrix are shown to improve magnetic flux pinning over wide range of magnetic fields. We first fabricate single phase of Sm2Ba4CuBiOy (Sm-2411) using a solid-state reaction and then introduced them into SmBCO single grains. Top seeded melt growth (TSMG) has been used to grow SmBCO single grains in air atmosphere. A significant improvement in Jc is observed, over wide magnetic fields, for single grains containing Sm-2411nano-phase inclusions when compared to that of SmBa2Cu3O7−δ/Sm2BaCuO5 composites. When compared to YBCO nano-composites, SmBCO composites are shown to exhibit high Jc at medium range of magnetic fields (1–2 T) at 77 K.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号