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1.
A high-pressure technique was adopted to obtain perovskite-type . A new perovskite was characterized to have a cubic symmetry with ; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement. 相似文献
2.
The discharge process was investigated on a lithium battery using as cathode. The battery works as primary battery. The potential gradually decreased from 2.1V to 1.8V upto a discharging of . Then it was almost constant at 1.8V until the discharging of about 2.0. Iodine is partially removed out of , keeping the host TaSe4 chain structure as it was in the first step of discharge. The new product has tetragonal crystal lattice having lattice parameters of and , which is twice of c-parameter of . 相似文献
3.
The A-site deficient perovskite was synthesized under the controlled atmosphere of CO2H2 mixed gas at 1350°C, and the structure was investigated by the powder X-ray diffraction method. The product is slightly oxygen deficient (, where 0.007 ≦ λ ≦ 0.079), and the structure is dependent on λ: when λ is small, the perovskite cell is distorted to orthorhombic symmetry and the unit cell is doubled along the c′ (> b′, a′) axis, while a cubic perovskite structure is facilitated with the increase of λ. A structural model, which calls for an ordered arrangement of the A-site vacancies along the c′-axis, is proposed and its order parameter is calculated from the intensities of the superstructure lines. 相似文献
4.
Crystals of were grown by chemical vapor transport of the elements from a charge zone maintained at 630°C. and a growth zone at 560°C. The crystals were characterized by chemical, x-ray, and densitometric techniques. is structurally related to the MIIPS3 thiophosphides. The compound is an insulator and has an optical absorption edge of 3.1(1) e.V. 相似文献
5.
The layered compound is studied by photoelectrochemical technique. Two modes of transition, indirect ~ 1.55 eV, and direct ~ 1.80 eV are evidenced. An estimation of the hole diffusion length is given through the use of Gärtner model (). The flat band positions of the junction at different pH values are determined in an electrochemical scale. 相似文献
6.
A new interpretation is proposed for the magnetic properties of perovskite-type iridium (+V) oxide . In its unusual +5 oxidation state iridium has a t42ge0g configuration. The magnetic susceptibility has been calculated assuming cubic symmetry of the crystal field and a Coulomb repulsion of the same order of magnitude than spin-orbit coupling. Fitting of the experimental data leads to a single spin-orbit constant close to that of previously investigated Ir(+V) compounds. 相似文献
7.
The effects of annealing on the structure and electrical conduction in semiconducting films were investigated. Annealing increases the product of the density of states and the mobility near the Fermi level, and this suggests that the mobility increases because of structural changes in the alumina matrix.Thermopower measurements allowed us to evaluate the asymmetry about the Fermi level of the product Nμ. 相似文献
8.
Crystals of were grown by chemical vapor transport of the elements. The phase is structurally related to the hyposelenophosphates, MIIPSe3, but contains both indium atoms and vacancies on the metal ion sites. The compound shows a high electrical resistivity (>108 ohm-cm) and has an optical absorption edge at 1.9 (1) e.V. 相似文献
9.
S. Nomura J. Kuwata S.J. Jang L.E. Cross R.E. Newnham 《Materials Research Bulletin》1979,14(6):769-774
The electrostriction in crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP2 above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q11 = 1.6·10?2m4/C2, Q12 = ?0.86·10?2m4/C2, and Q44 = 0.85·10?2m4/C2. 相似文献
10.
A. Rogalski 《Thin solid films》1980,67(1):179-186
heterojunctions with a long wavelength spectral cutoff (λc ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with RoA equal to 170 Ω cm2 and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given. 相似文献
11.
For high temperature creep, fatigue and creep-fatigue interaction, several authors have recently attempted to express crack growth rate in terms of stress intensity factor , where a is the equivalent crack length as the sum of the initial notch length a0 and the actual crack length , that is, . On the other hand, it has been shown by Yokobori and Konosu that under the large scale yielding condition, the local stress distribution near the notch tip is given by the fracture mechanics parameter of ), where a is the cycloidal notch length, σg is the gross section stress and ) is a function of σg. Furthermore, when the crack growth from the initial notch is concerned, it is more reasonable to use the effective crack length aeff taking into account of the effect of the initial notch instead of the equivalent crack length a. Thus we believe mathematical formula for the crack growth rate under high temperature creep, fatigue and creep-fatigue interaction conditions may be expressed at least in principle as function of and temperature.In the present paper, the geometrical change of notch shape from the instant of load application was continuously observed during the tests without interruption under high temperature creep, fatigue and creep-fatigue interaction conditions. Also, the effective crack length aeff was calculated by the finite element method for the accurate estimation of local stress distribution near the tip of the crack initiated from the initial notch root. Furthermore, experimental data on crack growth rates previously obtained are analysed in terms of the parameter of with gross section stresses and temperatures as parameters, respectively. 相似文献
12.
We consider constitutive relations of the form W(B,…, C) where W is a scalar-valued polynomial function which is invariant under the group which defines the symmetry of the crystal class . We make no restriction as to the number or kind of quantities appearing as arguments of . We list the multilinear elements of an integrity basis for functions of quantities φ, φ',…, x, y,… where φ, φ',…, x,y,… form carrier spaces for the irreducible representations Γ1,…, Γ'6 of . The elements of an integrity basis for functions of B,…, C are readily determined once these multilinear elements are given. We give examples and tables to facilitate the use of the results obtained here and in [1]. 相似文献
13.
A procedure is presented by which a modified WOL specimen can be designed to withstand the load required to achieve a , or test for a low yield strength, high toughness material, using information from the test of a standard WOL specimen that has suffered plastic collapse of its loading arms. The for the family of geometries used is obtained from published data fitted to a 2-dimensional half-power series, and the load point and guage point compliances are obtained through a connected beam model that is calibrated from existing compliance data to imitate a WOL specimen. Prom these calibrations the tensile component correction factor is evaluated and found to be applicable for this type of specimen. 相似文献
14.
Karl Markström 《Engineering Fracture Mechanics》1977,9(3):637-646
values for two medium-strength steels have been experimentally determined from tests on different types of specimen. Evaluation of test records was performed utilizing a digital computer. Two independent electrical methods were employed to determine critical points. Results indicate independence of on specimen configuration and hence support the suggestion that the be a relevant parameter for onset of crack growth. Present results compare favourably with previously published data. 相似文献
15.
The effect of specimen geometry and subcritical crack growth on the nonlinear energy fracture toughness, , has been examined for thin, center-cracked sheets of 2024-T3 and 7075-T6 aluminum alloys. The procedure followed was to independently vary the specimen length, L, width, w, andd crack length-to-specimen width ratio and to determine the toughness both at the onset of subcritical crack growth and at the initiation of unstable fracture. Comparisons were also made with the R-curve toughness, GR, evaluated at unstable fracture from which it was found that both and GR displayed the same trend of change with geometrical variables, with consistently higher than GR. When the nonlinear energy fracture toughness was evaluated at the onset of subcritical crack growth, it was found that the geometry dependence essentially disappeared.Scanning electron microscopic examination of some typical fracture surfaces showed that stable crack growth was accompanied by a gradual change of fracture mode from plane strain to plane stress. An analysis of possible errors in the experimental procedure showed that the scatter observed in values was not due to experimental errors, but apparently due to inhomogeneities in the materials. Several techniques were also introduced for the purpose of more directly incorporating crack growth into the determination, but it was found that they did not cause significant variation in the toughness values. 相似文献
16.
par Leïla Dogguy-Smiri Nguyen-Huy Dung Marie-Paule Pardo 《Materials Research Bulletin》1978,13(7):661-666
Twins of were used for crystal structure determination. Twinning is explained by a reticular pseudomerihedry. Axis, plane and obliquity of the twin have been determined. Cell dimensions are: ; ; α = β = γ = 90°; space group 14; Z = 2. The final R value is 0.059. The material is isostructural with CdGa2S4. 相似文献
17.
The objectives of this study were to determine whether the curve approach could be used to evaluate the ductile to brittle temperature performance of a high yield strength structural steel (HY130) and to demonstrate that the single specimen unloading compliance method is applicable to evaluate values and curves for compact specimens tested at temperatures from ?192 to 150°C. The major conclusions of this work are that and the complete curve can be obtained using the single specimen method over the above temperature range and that does define a ductile to brittle transistion temperature for HY130 steel which should be more valuable for structural design than that found from Charpy or dynamic tear specimens because it is based on a fracture toughness parameter. The comparison of the transition temperature and that from Charpy specimens shows that the Charpy transition temperture is more conservative for the HY130 steel tested. In transitional specimens which demonstrated a ductile crack tearing followed by a brittle failure, scanning microscope stereo pair fractography showed that the transition from ductile to brittle behavior was very gradual in comparison to the distinct crack tips obtained on ductile specimens broken in a brittle fashion at a cryogenic temperature. 相似文献
18.
A new compound with composition Cu0.75 VS2 has been prepared. Its preparation, X-Ray structure, electrical and magnetic properties are reported. The structure is related to the CdI2-type, as in the case of the previously described CuxTiS2 (1); in Cu0.75 VS2, Cu atoms are ordered in tetrahedral sites between the CdI2-type subunits, whereas in CuxTiS2 Cu atoms are disordered in two independent sites. The vanadium atoms are shifted with respect to the titanium sites which leads a monoclinic distortion of the hexagonal cell. The relation between the CdI2 unit cell and the true monoclinic cell of Cu0.75 VS2 is: In Cu0.75 VS2, vanadium atoms occupy two independent sites, three vanadium atoms forming a triangular cluster (V2—V3 distances are 2.91 Å and V3—V3 are 2.92 Å) while one vanadium atom is isolated ( and . The physical properties exhibit a transition at 50°K approximately, the magnetic susceptibility being temperature-independent above and temperature dependent below the transition (Curie-Weiss behavior). Resistivity and Hall measurements confirm the metallic nature of the compound and show the existence of the low temperature transition. The observed properties could be interpreted as a result of the low temperature localisation of the 3d electron of V1. 相似文献
19.
Existence of a solid solution, hexagonal -type, between and La6Ge2.5Se14 compounds. Location of the eutectic valleys and ternary eutectic (650°C, for La2Se3, 3 Ga2Se3, 14 GeSe2). Level curves of the liquidus.Obtention of glasses in a large domain of composition, along the eutectic valley. Measurements of Tg and crystallisation temperature. 相似文献
20.
Anders G. Nord 《Materials Research Bulletin》1983,18(5):569-579
A number of solid solutions of 3(PO4)2 in Cd3(PO4)2 have been prepared and equilibrated at 1070 K (). The respective ( phases are either isotypic with β′-Cd3(PO4)2 or with the mineral graftonite, both with five- and six- (or even seven)-coordinated cations. The monoclinic unit cell dimensions have been accurately determined from Guinier-Hägg photographs, and complete X-ray powder diffraction data are given for β′-Cd3(PO4)2. The cell volumes are strongly correlated to the size and amount of incorporated 2+ cation. The homogeneity regions and structures of the (Cd,)3(PO4)2 phases, though, seem rather to be controlled by the cation ordering. 相似文献