摘要:

AbstractThe paper presents problems of an application of grazing incidence X‐ray reflectivity as a tool for investigations of the surface roughness. The theoretical calculations are based on Fresnel theory. The surface roughness reduces the reflected amplitude therefore a damping factor describing an influence of that is introduced into equations. The results of computer simulations have been used for estimation of the measured surface roughness of thin epitaxial Si film and GaAs single crysta

ISSN:0232-1300    

DOI:10.1002/crat.2170320113

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe statistical atom model is used for abinitiocalculations of the atom binding energy in crystals. The original calculations by the above method of atomization energy atT= 0 K of theA1modification crystals ofIBelements group of the Periodic System are consistent with the experimental data. The atomization energy estimates of the A2, A3modifications are made.

ISSN:0232-1300    

DOI:10.1002/crat.2170320114

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe force dependence of the ball indentation hardness can be described in many cases by MEYER's hardness law. The characteristic material parameters are the MEYER constant K and the MEYER exponent n. But often other simple measures of hardness are used for technical applications. Examples are the difference of hardness for two different loads, which gives a good view of the hardening capability of the material, and the BRINELL hardness.It is shown that empirical found relations between the mentioned measures of hardness and the MEYER parameters are strong consequences of the validity of MEYER'S law. In special ranges of the values of the material parameters these empirical relations are linear ones. As a result of the theoretical considerations one must recommend to use the theoretical relations to fit the experimental values, because only in this case all physical conditions are fulfiled automatically.

ISSN:0232-1300    

DOI:10.1002/crat.2170320115

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe RBS/channelling technique was used to study the near‐surface damage characteristics of CuInSe2crystals after polishing with 0.05 μm grade alumina and subsequent annealing up to temperatures of 600 °C. A comparative RUMP and damage density depth profile analysis of the channelling spectra revealed a polish‐induced near‐surface disordered layer with a thickness close to 40 nm. Up to annealing temperatures of about 400 °C a gradual overall decrease of the defect density in the damaged layer is observed without detectable changes in its thickness. An indium‐rich surface layer is formed after vacuum annealing

ISSN:0232-1300    

DOI:10.1002/crat.2170320116

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractParts I and II investigated twins that form when a more favourable energetic transition structure initially occurs which then, at a certain growth stage (presumably in the nm‐range), transform into a more symmetric structural arrangement. These transition structures, which could explain the transformation between the twin individuals, were found using lattice energy calculations on organic substances such aspentaerythrite, 1,2,4,5‐tetrabromobenzene, 3,5‐dimethylbenzoic acid, andmaleic acid. The formation of a more favourable energetic but symmetrically lower transition structure is more likely. when lattice pseudosymmetries are present. Experimentally proving these transition structures is extremely difficult because of their low volume. It has nevertheless been possible to detect such a transition structure — around which crystal growth begins — in many metallic vapour‐deposit layers. Crystal growth begins around a core and then continues as a three‐dimensional periodically ordered cubic face‐centered structure, at which point twins form. In Part III, the attempt is made to confirm these processes with ener

ISSN:0232-1300    

DOI:10.1002/crat.2170320117

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractCertified reference materials (CRMs) are very important for the reliability of the results of chemical analyses and, at the same time, constitute the basis of comparability of analytical data. The development of a new type of CRMs is demonstrated using the example of porous and finely dispersed solids having specific surface area, specific pore volume, pore volume distribution, and mean pore radius as their characteristic values.Many of the properties of reference materials to be certified, such as their elemental content, are established by means of measurement procedures relying on different and independent principles of measurement. With porous or finely dispersed solids, however, the characteristic values referring to pores strongly depend on the size of the probe molecules used, a fact which is due to the fractal character of these substrates. This is particularly true for the specific surface area or the pore volume. As a result, when applying the method of gas adsorption, the certified values refer to a specific probe gas, e.g. to nitrogen. The use of other gases yields different numerical values for the characteristic values to be certified.Generally, the pore system of a solid contains pores of irregular shape. Therefore, depending on the presence of e.g. cylinder or slit pores, different evaluation models must be applied. For the verification of model calculation of microporous solids, zeolites with their crystallographically defined voids are particularly well suited. They can serve as a reference point for the correctness of the model used.

ISSN:0232-1300    

DOI:10.1002/crat.2170320118

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractIn powder mixtures of ZnO and TiO2the compounds Zn2TiO4, ZnTiO3and Zn2Ti3O8can be formed as a result of solid state reactions. The mechanism of the double oxide formation is essentially determined by the microstructure of the powder mixture. Furthermore, the kind of the double oxide depends on the TiO2‐modification. There exist structural similarities between Zn2TiO4(spinel) and TiO2(anatase) on the one hand and ZnTiO3and TiO2(rutile) on the other hand. The compound Zn2Ti3O8is formed only on the basis of the Zn2TiO4‐phase. The crystal structure of Zn2Ti3O8was derived as a defect spinel. The unoccupied sites of cations are not arranged statistically, but they are ordered in the structure. This order leads to the decrease of the space group symmetry from Fd‐3m to

ISSN:0232-1300    

DOI:10.1002/crat.2170320119

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe possibilities of modelling of irregular interstratified structures of single crystals with chemical inhomogeneity are discussed: the theoretical basis, the requirements to the X‐ray experiment, the accuracy and reproducibility of the diffraction data, the reliability of the suggested models. The examples of the successful application of the approach to the study and description of the defect structures of single crystals belonging to different structural types are considered. Three general types of irregular interstratified structures differing in the nature of chemical inhomogeneity as well as in the peculiarities of their diffraction patterns are distinguishe

ISSN:0232-1300    

DOI:10.1002/crat.2170320120

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA new growth method, based on a vapour‐liquid‐solid (VLS) mechanism, is reported for preparing single crystals of N‐methylurea (NMU), a material which appears to be a good alternative to urea for non‐linear optical applications in the “near UV‐visible” region of the spectrum. Details of the growth procedure are given and it is shown that large single crystals, with volumes up to 7 ÷ 10 cm3, can be obtained with satisfactory reproducibility and very fast growth rate. Structural and optical characterisation, still preliminary, are reported, which evidence a crystalline quality comparable to that of urea and N‐methylurea as previously grown with other growth techniques. Cryst. Res. Technol.

ISSN:0232-1300    

DOI:10.1002/crat.2170320121

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170320102

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY