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1.
The existence of twin domains in YBa2(Cu1?xCo x )3O y samples was confirmed by many experiments. However, the physical picture of the twin domains has not been reported up to now. By analyzing oxygen content, Cu and Co valences, and Co coordination in those samples, we propose a domain model, which consists of two pairs of parallel zigzag Co-O chains surrounding orthorhombic cells, one along (110) direction and the other along (110) direction. The zigzag Co-O chains are the twin walls, with neighboring walls perpendicular and the opposite ones parallel. The distance between parallel walls (i.e., zigzag Co-O chains) depends upon Co concentration of sample. The twin domain model predicts the geometry, size, and absence of systematic symmetry of the domains. The model also predicts the modulation periodicity of electron diffraction patterns, which depends on Co concentration. All the predictions by the model agree well with the experimental results reported in literatures. Furthermore, the model indicates the possible existence of two domains, which have incommensurable modulation periodicity.  相似文献   

2.
The thermal conductivity of Er x Sn1 ? x Se solid solutions has been measured at temperatures from 80 to 360 K. The results have been used to evaluate the electronic and lattice components of thermal conductivity for elastic carrier scattering, parabolic bands, and arbitrary degeneracy. With increasing erbium content and temperature, both the electronic and lattice components decrease considerably. Long-term annealing increases both components. It follows from the present experimental data that heat conduction in Er x Sn1 ? x Se is mainly due to phonons and that the observed rise in thermal resistance with Er content is due to phonon-phonon and paramagnetic-ion scattering.  相似文献   

3.
p-Si1 ? x Ge x crystals have been diffusion-doped with gold. Gold diffusion in the p-Si1 ? x Ge x 〈Au〉 samples and their electrical properties have been studied. The results demonstrate that the highest gold concentration in the crystals can be achieved in the temperature range 1000–1050°C. An expression has been derived which indicates that, all other factors being the same, compensation with Au, an amphoteric impurity, insures better homogeneity compared to codoping with acceptor and donor impurities. The hole concentration homogeneity in gold-compensated samples is at the same level as or even better than that in the uncompensated material.  相似文献   

4.
We have studied in detail the coupled phonon-plasmon mode Raman spectra of n-In x Ga1 − x As with n in the range 1017 to 1019 cm−3. The results indicate that the behavior of the high-frequency mode L + can be described in terms of coupled modes in the Drude approximation. The proposed theory and experimental data are used to estimate the carrier concentration in the solid solution and its composition.  相似文献   

5.
The thermovoltaic effect in films of variband solid solution Si1–x Ge x (0 ≤ x ≤ 1) has been observed for the first time. The samples comprised n-Si–p-Si1–x Ge x (0 ≤ x ≤ 1) heterostructures grown by liquid phase epitaxy. An electromotive force within 0.05–0.3 mV and a current of 0.0025–0.0035 μA appeared on heating samples in a temperature range from 40 to 250°C.  相似文献   

6.
The properties of AgCl1 - x Brx ( x = 0.5-0.8) solid solutions prepared by the Bridgman-Stockbarger method are studied using a variety of techniques (x-ray diffraction, microstructural examination, chemical analysis, and x-ray microanalysis). The lattice parameter of the solid solutions is found to exhibit a negative deviation from additivity. The effects of composition and preparation conditions on the structural properties of the solid solutions are discussed. The structural characteristics of abrasively polished surfaces of the samples are shown to be influenced by the preparation conditions.Translated from Neorganicheskie Materialy, Vol. 41, No. 1, 2005, pp. 78–87. Original Russian Text Copyright © 2005 by Artjushenko, Baskov, Golovanov, Kuzmicheva, Lisitskii, Musina, Polyakova, Sakharov, Sakharova.  相似文献   

7.
Cr1?x V x Te solid solutions with a hexagonal structure (NiAs type) have been obtained in the composition range x = 0?0.4 by direct melting of elemental mixtures, followed by annealing and quenching. The 80-K magnetic moment is found to decrease from 2.4μB in CrTe to 1.52μB in Cr0.6V0.4Te. The Curie temperature varies from 342 K to 321 K, respectively.  相似文献   

8.
The optical and transport properties of Fe2+-doped Cd x Hg1?x Se crystals with a midgap Fe2+ level have been studied. The results demonstrate that Fe2+ ions influence both the optical and transport properties of Cd x Hg1?x Se〈Fe2+〉. The observed optical absorption bands are due to a donor Fe2+ level in the band gap, with a depth E Fe = 0.21 eV, and to band-band transitions. Thermal anneals in Hg and Se vapors have different effects on the carrier concentration and mobility in the crystals. The effect of annealing on the transport properties of the Fe2+-doped crystals differs from that for undoped crystals and is governed by the state of point defects.  相似文献   

9.
The optical properties of diamond-like carbon (DLC) films obtained by plasmachemical deposition on Cd1 − x Zn x Te (x ∼ 0.04) single crystals have been studied by ellipsometry. The ellipsometric data have been interpreted within the framework of a three-layer model of the DLC film-semiconductor crystal refractory system with transition layers between the film and substrate. It is found that DLC films exhibit antireflection properties in this refractory system in the IR spectral range. It is established that the proposed antireflection film-substrate structure is stable with respect to thermal cycling and ultrasonic treatment.  相似文献   

10.
Plasma deposition has been used to grow Si1?x Ge x :H(x= 0 ? 1) films, undoped and doped with PH3 or B2H6, for p-i-n solar cells and other optoelectronic applications. The optical, electrical, and photoelectric properties of the films have been studied at constant hydrogenation and doping levels. The films deposited under appropriate conditions are amorphous, and three-layer solar cells fabricated from such films offer an efficiency of 9.5% at an illumination of 100 mW/cm2. The photoresponse of the a-Si1 ? x Ge x :H films strongly depends on Ge content. The hydrogen concentration in the films was controlled by varying the gas phase composition and was determined from the IR absorption in the films.  相似文献   

11.
We have identified conditions that ensure the preparation of ultrafine Sr1 − x Nd x F2 + x powders uniform in phase composition. The powders were characterized by X-ray diffraction and scanning electron microscopy. The powder particles have the form of faceted nano- and microcubes and range in size from 30–100 nm to 0.3–2.5 μm, depending on precipitation conditions.  相似文献   

12.
We present systematic studies of the magnetocaloric properties of the polycrystalline La1−x Ca x MnO3 system for x = 0.3, 0.35, and 0.4 near a second-order phase transition from a ferromagnetic to a paramagnetic state. The crystal structure of the studied manganites was shown to be in good agreement with previous reports. The value of the magnetocaloric effect has been determined from the measurement of magnetization as a function of temperature and external magnetic field. The maximum entropy change detected in La0.7Ca0.3MnO3 at a field of 2 T reaches 8 J/kg K which exceeds that of gadolinium. In all studied samples, the paramagnetic–ferromagnetic transition is very narrow but no hysteresis is observed and the transitions are identified as second-order ones. The phase transition in La0.7Ca0.3MnO3 appears to be almost of first-order.  相似文献   

13.
Superconducting Cu x TaSe2(x=0.05, 0.15) and Cu0.15TaSe2?x S x (x=0, 0.5, 1, 1.5) single crystals have been systematically fabricated by a chemical vapor transport method. It is found that the double doping in TaSe2, i.e., the simultaneous intercalation of Cu and substitution of Se by S, can substantially enhance the superconducting transition temperature. Transport property measurements give evidence of the coexistence and competition of charge density wave state and superconductivity in Cu x TaSe2 which provide meaningful information to understand the complex electronic states in this system. The parallel shift and the fan-shape broadening behaviors are observed in the superconducting transition curves under magnetic fields of Cu0.15TaSeS and TaSeS, respectively, indicating an increase of coherence length and suppression of superconducting fluctuation induced by copper intercalation.  相似文献   

14.
Nanostructuring in fluorite-like Ca1 ? x La x F2 + x is shown to be associated with the precipitation of an CuAu-ordered phase. The shape of the precipitates is governed by the energetics of the {001} and {111} faces of tetragonal inclusions in highly anisotropic media and is nearly cuboctahedral. The misfit strain relaxes through the generation of twins, which nucleate along the intersection lines of {001} and {111} faces. The twins impede facial development and further growth and ordering of precipitates, thereby freezing the precipitation process in its initial stage. For this reason, the phase segregation is difficult to reveal, and Ca1 ? x La x F2 + x crystals appear homogeneous.  相似文献   

15.
(1 ? x)(K0.5Na0.5)NbO3xBi(Mg0.75Mo0.25)O3 [(1 ? x)KNN–xBMM] (x?=?0.005, 0.01, 0.02) ceramics were prepared via a solid-state reaction method. X-ray diffraction patterns (XRD) and Raman spectrum showed that a solid solution was formed between the BMM and KNN, which improved the electrical properties of KNN. With increasing the BMM content, the grain firstly increased and then decreased. When x?=?0.01, the ceramics exhibited the optimized microstructure, indicating that there exits an optimal doping component. Temperature dependence of relative permittivity also increases firstly and then decreases. The relative permittivity (εr) of ~?1418 in stabilization zone, εmax?~?4861 at the Curie temperature T C ~ 394 °C, good temperature stability ?ε/ε123 °C?≤?±?15% from 123 °C to 348 °C, and the dielectric loss tanδ?≤?0.036 from 109 to 348 °C were obtained for 0.99KNN-0.01BMM ceramics. Conductivity behavior of the (1 ? x)KNN–xBMM was investigated as a function of temperature from 420 to 520 °C and frequency from 40 to 106 Hz, showing that the basic mechanisms of conduction and relaxation processes were thermally activated, and oxygen vacancies were the possible ionic charge transport carriers at higher temperatures.  相似文献   

16.
The interaction of R1 – xZr x (R = La, Ce, Nd, Dy; x = 0–0.05) silicides with hydrogen has been studied at hydrogen pressures of up to 250 MPa. At a high pressure and a temperature of 20°C, hydrogen solubility in the solid phase is very low. Raising the reaction temperature leads to disproportionation of the silicides. According to X-ray diffraction data, the disproportionation reaction yields a rare-earth hydride and RSi2 disilicide.  相似文献   

17.
The temperature dependences of the thermal expansion coefficient and isothermal compressibility for TlGaSe2(1 ? x)S2x (x = 0.1, 0.2) solid solutions show an anomaly attributable to a second-order phase transition. The thermal expansion data have been used to evaluate the Debye characteristic temperature Θ, rms atomic displacement, and specific heat difference of the solid solutions.  相似文献   

18.
We have studied the growth and structure of epitaxial films of Cd1–xMnx (x = 0.03) diluted magnetic solid solutions grown on mica substrates by molecular beam epitaxy and identified conditions for producing n- and p-type epitaxial films. Using an additional Te vapor source and optimizing the substrate temperature in the growth process, we were able to obtain structurally perfect p-type Cd1–xMnxTe (x = 0.03) films with clean, smooth surfaces. The growth plane of the films on the mica substrates is (111) of a face-centered cubic lattice and their unit-cell parameter is а = 6.477 Å.  相似文献   

19.
Mn x Hg1 ? xTe (x = 0.05, 0.12) single crystals were grown by solid-state recrystallization, and their axial and radial homogeneity was assessed by optical, electrical, and electron-microscopic measurements. The crystals are p-type, with a hole concentration of (4.3–5.3) × 1022 m?3 and Hall mobility in the range (410–570) × 10?4 m2/(V s).  相似文献   

20.
WS2 is a promising catalyst for the hydrogen evolution reaction. We have explored photocatalytic properties of ternary sulphoselenides of tungsten (WS x Se 2?x ) by the dye-sensitized hydrogen evolution. WS x Se 2?x solid solutions are found to exhibit high activity reaching 2339 μmol h?1 g?1 for WSSe, which is three times higher than that of WS2 alone (866 μmol h?1 g?1 ). The turnover frequency is also high (0.7 h?1 ). Such synergistic effect of selenium substitution in WS2 is noteworthy.  相似文献   

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