摘要:

The physical processes are examined which can be used for the detection of X‐rays in the range between about 3 and about 20 keV and for the positional localization of the incident photons. The criteria for choosing a detector for particular purposes are discussed in general terms. Specific examples of one‐ and two‐dimensional detectors are then considered with particular emphasis on devices which are still in a state of development, and an attempt is made to summarize the nature, performance and suitability for different experiments of available de

ISSN:1600-5767    

DOI:10.1107/S0021889886089732

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

In order to determine short‐range order in a solid solution from diffuse X‐ray or neutron diffraction experiments the separation of atomic size effects from the experimental data is a crucial problem. It is demonstrated by a model calculation that a clear improvement of the separation method proposed by Borie&Sparks is obtained if the range of measurement is extended to include the first Brillouin z

ISSN:1600-5767    

DOI:10.1107/S0021889886089720

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

The theoretical feasibility of differentiating high‐resolution electron microscope images obtained at Sherzer focus for two crystals of the same chemical composition [Pb6Ca4(PO4)6(OH)2] has been investigated for two commercially available electron microscopes: the Jeol 4000 EX microscope (Cs= 0.48 mm,V= 400 kV) and the Jeol 200 CX microscope (Cs= 1.2 mm,V= 200 kV) and at the following resolutions: 1.4, 2.0 and 2.5 Å. In these crystals the lead atoms are distributed either preferentially in the Ca(2) sites [Pb6(2)Ca4(1)(PO4)6(OH)2] or evenly in both Ca sites [Pb3.6(2)Ca2.4(2)Pb2.4(1)Ca1.6(1)(PO4)6(OH)2]. Crystals of various thicknesses oriented along the [20]crystallographic direction have been investigated. The results show differences between images of the two structures, which are more marked when the crystal thickness is increased. A compromise between medium and ultra‐high resolution had to be reached for interpretation of th

ISSN:1600-5767    

DOI:10.1107/S0021889886089719

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

The structural changes associated with the precipitation of metastable and equilibrium phases during decomposition of three supersaturated Al‐rich Al–Ag–Mg alloys at 393, 456 and 508 K have been established by analysing the diffraction of monochromatic X‐radiation by single‐crystal alloy plates. Precipitated phases observed were: (a) in the Al–0.54 at.% Ag–4.49 at.% Mg alloy, type 1 Guinier–Preston zones,T′ phase,Tphase; (b) in the Al–0.87 at.% Ag–1.80 at.% Mg alloy, type 1 Guinier–Preston zones, type 2 Guinier–Preston zones (a newly observed body‐centred tetragonal compound,a= 4.13,c= 8.60 Å, space groupI41/amd),T′ phase,ηphase; (c) in the Al–1.30 at.% Ag–1.05 at.% Mg alloy, type 1 Guinier–Preston zones, type 2 Guinier–Preston zones,γphase. Volume fractions of the precipitated phases, sizes of the precipitates and orientations of cell axes relative to the axes of the Al lattice are given for v

ISSN:1600-5767    

DOI:10.1107/S0021889886089707

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

A model is proposed for calculating the Rayleigh‐wave velocity as obtained by an acoustic lens, taking into account the anisotropy of the material under study and the profile of the miniature acoustic probe. The results obtained by this model on different `cuts' of single‐crystal silicon agree with both those published in the literature and our own experimental results. In addition, the model has been applied to the non‐destructive thickness measurement of opaque thin films deposited on different anisotropic substrates. More significantly, using the model and experimental acoustic material signature (AMS) curves obtained with this acoustic measurement system, the thickness of tungsten thin films deposited on silicon (100) have been measured. The results are in good agreement with measurements made using a Rutherford back‐scattering te

ISSN:1600-5767    

DOI:10.1107/S0021889886089690

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

The diffuse scattering in a volume in reciprocal space from NbC0.72was measured on an absolute scale at two synchrotron sources (in the US and in Japan) and with a high‐intensity rotating‐anode source (in Japan). The shape and actual absolute intensities agreed to a few percent. Special problems associated with such measurements at a synchrotron are noted, especially with an insertion device. The high resolution possible at such sources reduces the need for an evacuated sample chamber. Detailed measurements can be completed in 1–2 d, making such studies much more accessible than is possible with sealed‐tube X‐ray

ISSN:1600-5767    

DOI:10.1107/S0021889886089689

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

The oscillatory deviations with respect to the Porod asymptote, observed in the small‐angle X‐ray intensities scattered by some selenium ruby glasses, are explained in terms of a finite discontinuity of the second‐order derivative of the correlation function. The best fit of the intensity allows the value of the discontinuity to be determined as well as the point at which it occurs. The physical implications of these results are disc

ISSN:1600-5767    

DOI:10.1107/S0021889886089677

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

The interpretation of a relationship between measured intensities and the radial distribution function given in the paper `The accuracy of experimental radial distribution functions for metallic glasses' [Thijsse (1984).J. Appl. Cryst.17, 61–76] is dispute

ISSN:1600-5767    

DOI:10.1107/S0021889886089665

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

Comments made by Hajdu&Herms [J. Appl. Cryst.(1986).19, 198–199] on the original paper by Thijsse [J. Appl. Cryst.(1984).17, 61–76] are replied

ISSN:1600-5767    

DOI:10.1107/S0021889886089653

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY

摘要:

The measurement of the mean‐square thermal displacement 〈u2〉 of carbon atoms in highly oriented pyrolytic graphite (HOPG) in the hexagonalcdirection is reported. Energy‐dispersive X‐ray diffraction (EDXD) has been used to study the integrated intensity of all Bragg reflections 004 through 0′0′14 as a function of temperature. It is demonstrated that the correction of the Bragg intensities due to thermal diffuse scattering contributions is very important for HOPG, when EDXD is used. The Debye temperatureΘD= 554 (30)

ISSN:1600-5767    

DOI:10.1107/S0021889886089641

出版商:International Union of Crystallography    

年代:1986

数据来源: WILEY