摘要:

X‐ray topography studies of scratches on discs of silicon crystals gave the following results. The damage field of each scratch consists of three zones of different kinds of distortions and exceeds the furrow dimensions in width as well as in depth by several orders of magnitude. Surrounding each scratch there exists a compressive strain of the order of 2.103 kp.cm−2attributed to microplastic deformation. No influence of scratching velocity on the resulting damage is observed. An `impressing' action of the scratching tool while in motion is much more effective in producing damage than a `ploughing

ISSN:1600-5767    

DOI:10.1107/S0021889872009136

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

Various characteristic lattice defects in silicon have been recorded by some of the main X‐ray topographic methods (Bragg and Laue case, scanning‐ and fixed‐crystal techniques, single and double diffraction, hard and soft radiation), with the same specimens used for all methods. The comparison of the results allows some general statements on the qualification (advantages and disadvantages) of each method for detecting and investigating different kinds of lattice de

ISSN:1600-5767    

DOI:10.1107/S0021889872009148

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

Si(Li) semictors developed for nuclear spectrometry have achieved energy resolutions of a few hundred eV compared with the keV of the conventional detector for X‐ray spectrometry or diffractometry. So far, commercially available equipment incorporating a liquid nitrogen tank is too heavy and cumbersome for existing spectrometers and diffractometers. We have redesigned a Si(Li) probe suitable to replace scintillation or gas proportional counters on any conventional equipmen

ISSN:1600-5767    

DOI:10.1107/S002188987200915X

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

The micropore system of glassy C atoms has been characterized by a number of structural parameters obtained from X‐ray small‐angle scattering. The pore sizes and pore shapes are very similar to those already observed in other non‐graphitizing C atoms, notably carbon fibres. The results suggest that the pore shape is needle‐like with sharp edges and that the pore structure stems from a felt‐like entanglement of stacks of ribbon‐shaped ca

ISSN:1600-5767    

DOI:10.1107/S0021889872009161

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

The lattice parameters of BiFeO3were determined with the Straumanis method. At 25–13±0.02 °C, the hexagonal parameters areah= 5.5799±0.0003, andch= 13.8670±0.0005 Å. The temperature dependence of the lattice parameters in the range 20–325 °C is given by the equations:ah= 5.5764 Å + 6.06 × 10−5t, andch= 13.8620 Å + 2.10 × 10−4t. In the range of 344–838 °C, the lattice parameters obey the following equations:ah= 5.5946 + 6.83 × 10−5 t, andch= 13.7251 + 9.05 × 10−4 t−12.503 × 10−7 t2+ 9.40 × 10−10 t3− 3.57 × 10−13t4. By extrapolation of the angular separation of the 11.0 and the 10.4 reflections, the

ISSN:1600-5767    

DOI:10.1107/S0021889872009173

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

TheN(z) distribution, the Wilson ratio and variance values have been determined for the case of twinned crystals where non‐equivalent reflexions coincide exactly. The results have been applied to a practical example. The structural reasons for twinning may require that only reflexions occurring at relatively large Bragg angles be included in any statistical survey if the greatest discrimination is to be expecte

ISSN:1600-5767    

DOI:10.1107/S0021889872009185

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

By means of several low temperature devices the solid hydrous phases of the AgI–NaI–H2O system have been extensively studied by X‐ray diffraction, transmission Laue photography, and polarizing microscopy. The density, composition and unit‐cell parameters have been determined for three distinct AgI–NaI hydrates for which the stability regions correspond to phasesC,E, andFpreviously reported by Davis [J.Atmos. Sci. (1969),26, 1042]. The cell assignments are based on determinations of axial ratios from the Laue photographs and interplanar spacing analyses utilizing the Hesse–Lipson technique, Cohen cell‐parameter refinement and the de Wolff cell‐reliability criteria. All phases are of the composition AgI–NaI–nH2O with phaseCat 25 °C havingn= 4, ρ = 3.0 g.cm−3(measured and calculated) and indexing on the basis of a monoclinic cell with parametersa0= 7.573,b0= 9.454,c0= 12.403 Å, and β = 92.43° withZ= 4. PhaseFat −10 °C is also monoclinic witha0= 5.757,b0= 13.563 andc0= 12.541 Å and β = 103.05° withZ= 4, andn= 4. PhaseEappears to consist of two structures, very similar but differing in cell volume by 2.8%. We believe this to be due to varying water content, then= 3 phase being metastable. The cell reliability factor is less than 10 for both cells

ISSN:1600-5767    

DOI:10.1107/S0021889872009197

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

New lattice parameter and density results have been obtained for alloys in the β‐NiAl and 6‐Ni2Al3phase fields of the nickel–aluminium system. The lattice parameter of the β‐NiAl phase (CsCl‐type) falls linearly from 2.8870 Å at 50 at.% Ni to 2.8618 Å at 66. at.% Ni, with 2.00 atoms per unit cell. On the other hand, the lattice parameter on the Al‐rich side of NiAl falls linearly from 2.8870 Å to 2.8652 Å, while the number of atoms per unit cell falls from 2.00 to 1.817 by the creation of vacancies in normally nickel sites. The trigonal 6‐Ni2Al3phase‐structure, which is essentially an extension of cubic β‐NiAl, but with every third plane of nickel atoms perpendicular to the trigonal axis missing, shows a minimum in theaandcspacings at stoichiometric Ni2Al3. Density measurements indicate that the vacancies formed by the missing planes are progressively filled as nickel is added to Ni2Al3, but that a substitutional solid solution is formed on the aluminium‐rich side of stoichiometric Ni2Al3with aluminium replacing nickel atom by atom. In the NiAl phase, the number of valence electrons increases from 2.28 per unit cell at 61.9 at.% Ni to 3.00 at stoichiometric NiAl, and remains constant at 3.00 as the vacancies form until Ni2Al3is reached, at which stage the number of vacancies will have reached a maximum when there are only 1.67 atoms per pseudo‐cubic cell. The number of electrons per pseudo‐cubic unit cell then begins to rise and reaches th

ISSN:1600-5767    

DOI:10.1107/S0021889872009203

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

The combined action of pressure and temperature on aluminium‐rich alloys in the β‐NiAl field produces an increase in density and lattice parameter as a result of vacancy‐filling. Thus at 43.7 (4) at.% Ni, a pressure of 78 kbar at 1000 °C will increase the density of the alloy from 5.16 to 5.37, with a concomitant increase in lattice parameter from 2.8593 to 2.8712 Å and an increase in atoms/unit cell from 1.77 (5) to 1.87 (7). Similar density changes and increases in atoms/unit cell occur in the trigonal δ‐Ni2Al3phase structure, but in alloys on the aluminium‐rich side of stoichiometric Ni2Al3vacancy‐filling can actually lead to a reduction in both theaandcparameters. This may result from promoting electrons in the 3dshell of nickel into the conduction band, thereby re

ISSN:1600-5767    

DOI:10.1107/S0021889872009215

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

A small‐angle X‐ray scattering study of glassy GeO2is reported. Data were obtained from 4π sinθ/λ = 0.05 to 2.0 using a Kratky camera. The SAXS intensity decreased monotonically with decreasing angle from the main diffraction peak, and was not noticeably changed by hydrofluoric acid surface treatment or various annealing treatments. The intensity scattered at the smallest angle was 49±2.5 e.u. molec−1. Extrapolated to zero angle, the intensity corresponds to root‐mean‐square density fluctuations of 10−12V−1/2 cm−3/2, a value close to that expected from the thermodynamic fluctuation theory of liquids. A parallel study of fused silica has indicated mean‐square density fluctuations similar to those found in GeO2. The results are taken as evidence contrary to representations of structure based on specific arrays differing significantly from t

ISSN:1600-5767    

DOI:10.1107/S0021889872009227

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY