摘要:

A new general analytical method is suggested for identifying a crystal system from a powder X‐ray pattern with a computer. The formulae relating interferential indices and interplanar spacing of a line with the definite ratio of parameters of the Bravais cell for each crystal system are given. The identification of the system is carried out by selection of three definite lines, indices and interface distances, all of which satisfy the corresponding formula

ISSN:1600-5767    

DOI:10.1107/S0021889869007126

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The variance of theKα12doublet of iron X‐radiation as a function of truncation range was determined using a silicon analysing crystal. The presence of satellite lines gives rise to an initial `pseudolinear' part to the variance–range curve; the origin and significance of this part are discussed. The effect of the satellite group was removed by interpolation of the line profile. The possibility of locating the background level by computation is investigated; it is shown that a mis‐setting in the background level has an appreciable effect on the variance function, whilst a mis‐setting in the background slope has negligible effect on the slope of the variance function. Results for both filtered and unfiltered radiation a

ISSN:1600-5767    

DOI:10.1107/S0021889869007138

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

A previously given analysis of the beam and specimen tilt errors in the Bond single‐crystal method of lattice parameter determinations is extended to give a simple generalized treatment. This shows that the error passes through a maximum in accordance with an empirical observation by other workers. Crystal alignment procedures are examined in the light of the result

ISSN:1600-5767    

DOI:10.1107/S002188986900714X

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The practical importance of tungsten monocarbide prompted an investigation into its wear mechanism. Initial studies on ball‐milled tungsten carbide powders revealed considerable plastic deformation, coupled with a reduction in crystallite size. Deformation stacking faults, involving slip on the basal plane, were observed. The work was extended to sintered blocks, tool tips and single crystals. Studies on the worn surfaces of these revealed plastic deformation that extended to a depth of a few microns below the surface. The plastic deformation is an important factor in the wear of tungsten carbid

ISSN:1600-5767    

DOI:10.1107/S0021889869007151

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

X‐ray diffraction analyses of polycrystalline samples of Ca3TeO6and Ca3WO6have shown these compounds to be isostructural with Ca3UO6(space groupP21

ISSN:1600-5767    

DOI:10.1107/S0021889869007163

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

A comprehensive device for the electronic measurement of the distribution of electrons in both electron micrographs and diffraction patterns is described. Electrons are detected individually while the image or pattern is scanned across the fixed electron detector, and the resulting information is displayed by a storage oscilloscope and recorded by a chart recorder or punched paper tape. Provision is made to select the energy of the electrons passed to the detector, allowing pictures to be obtained at a given energy level or the energy loss spectrum of a specimen to be examined. Representative results are given.

ISSN:1600-5767    

DOI:10.1107/S0021889869007175

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

A storage oscilloscope has been attached to the IBM 1800 computer that is used for pole‐figure data acquisition. It allows fast plotting of pole figures by modulation of the cathode ray beam according to the pole density as it scans the stereographic projection along a spiral path. The time needed to plot the pole figure is reduced by a factor of eight as compared with a mechanical plotte

ISSN:1600-5767    

DOI:10.1107/S0021889869007187

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

In Berg–Barrett micrographs of twinned crystals whose structure is slightly distorted from cubic, a characteristic pattern of white and dark bands appears due to small changes of orientation of the reflecting planes; the appearance of these bands depends on which lattice planes are used for reflection. The orientations of the crystallographic axes in the individual twin components can be determined from a knowledge of the relative magnitudes of the tilt angles in various twinned lattice planes, and from a study of the widths and contrast of bands in the images from different Bragg reflections from the same crystal face. This method has been developed for twins appearing in rhombohedral and tetragonal structures, and applied to antiferromagnetic NiO and ferroelectric BaTiO3crystals in order to identify microscopic domain

ISSN:1600-5767    

DOI:10.1107/S0021889869007199

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The constitution of the Ni–Cd phase‐diagram has been explored by X‐ray diffraction and microscopy, principally at its high‐nickel end, but also with reference to the overall system. No primary solid solubility of Cd in Ni exists. The NiCd (β) compound equilibrates directly with nickel, with no further compound intervening. The unknown crystal structure of NiCd has been determined as being of the η‐carbide (E93) type, witha0(typically) = 11.387 Å and X‐ray density 9.18 g.cm−3. NiCd has a small homogeneity range and decomposes peritectically at about 680°C. The only other compound occurring in the system is Ni5Cd21(γ). An earlier reported `Ni2Cd5' (γ) could not be confirmed, though γ′ could compositionally be a dimorph to γ. Three‐phase coexistence of Ni, NiCd and Ni5Cd21can occur unstably or in segregation, the constitution being sensitive to heat‐treatment and to the large vapour‐pressure differences. NiCd seems to represent a new class of η‐carbide type intermetallic phases, in containing anon‐transition metal and excluding anyearly‐Group transition metal (e.g.IVA) so far thought to be essential. The wider implications of NiCd having this type structure are discussed briefly, and the (high Fe, Co, Ni, Cu)–(

ISSN:1600-5767    

DOI:10.1107/S0021889869007205

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The axial thermal expansion of monoclinic and tetragonal ZrO2and of monoclinic HfO2was studied over the temperature range from room temperature to 1400 °C. The linear thermal expansion coefficients were calculated. Thermal expansion along (x 106per °C)a= 10.31 monoclinic ZrO2, 11.60 tetragonal ZrO2, 9.34 monoclinic HfO2;b= 1.35 monoclinic ZrO2, – tetragonal ZrO2, 2.98 monoclinic HfO2;c= 14.68 monoclinic ZrO2, 16.08 tetragonal ZrO2, 13.10 monoclinic HfO2. Some aspects of the present study, such as anisotropy of thermal expansion and a pretransformation vibrational anomaly, are discussed brie

ISSN:1600-5767    

DOI:10.1107/S0021889869007217

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY