摘要:

AbstractThis article presents data on the impurities influencing the β → α transformation of high purity tin (99.9995%): temperature of the α → β transition‐T0, nucleation and α‐cr

ISSN:0023-4753    

DOI:10.1002/crat.19790140202

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe effects of doping of Ca and Ba (∼ 0.02 at %) upon the dislocation distribution in melt grown KCl crystals without cellular segregation were studied by an etch pit method in connection with the dispersion state of the dopants, which was examined by the dark field illumination. – (1) In the Ca‐doped crystal, in which the dopants were distributed uniformly, the formation of subboundaries was completely suppressed and dislocations were distributed at random. (2) In the Ba‐doped crystal, however, the dopants were non‐uniformly distributed and the dislocations tended to form subboundaries. The dislocations within the subgrains were distributed in a non‐uniform manner. (3) The dislocation density in the Ba doped crystal was higher than that of undoped or Ca‐doped crystal. This was explained by the mechanism similar to the Tiller's prediction. – Finally, the stress distribution due to the concentration fluctuation was examined by the birefri

ISSN:0023-4753    

DOI:10.1002/crat.19790140203

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe suitability of gelatin gel for the growth of good quality single crystals of potassium perchlorate has been investigated. Growth in a more rigid and simple apparatus has been accomplished and described here. The grown crystals were identified by X‐ray analysis. A study of the relation of crystal morphology to concentration of feed solutions and growth temperature has also been made. Studies made on chemical etching of the cleavages have revealed that the crystals are relatively perfect. At times, large liquid inclusions which introduce stresses in the crystals are responsible for a large dislocation concentratio

ISSN:0023-4753    

DOI:10.1002/crat.19790140204

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe phenyl‐trimethin‐merocyanine crystallizes in the space group I4with 8 molecules per unit cell. The lattice constants area=b= 16.121 Å,c= 6.549 Å, α = β = γ = 90°. The intensities were measured with an automatic single crystal diffractometer. The solution of the structure was obtained by applying the convolution molecule method and the R‐value method. The refinement was performed by least‐squares blockdiagonal method to an R‐value of 7.2% for 1067 independent reflexions. The C–C‐bond lengths within the plane of the trimethin chain alternate as in the molecule structure of the morpholylpentamethine‐merocyanine and thus point to a distinct polyenic behaviour. The valence angles within the chain alternate as well. This property indicates a polymethinic behaviour of the molecule. The geometry of the molecule proves the merocyanines to have an intermediate position between the polymethinic and the polyenic state. For a more detailed discussion we refer to the discussion of the morpholyl‐pentamethin

ISSN:0023-4753    

DOI:10.1002/crat.19790140205

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractUsing optical microscopy and TEM methods as well as X‐ray topography method structural perfection of Czochralski grown Se‐doped InSb single crystals has been investigated. Se concentration was determined by mass‐spectrometry method and was in the range of 1.1017to 9.1019cm−3. – It has been shown that Se presence up to the highest concentration does not influence crystal dislocation structure, but gives rise to the large number of precipitates showing moiré contrast. The size of the precipitates is in the range of 0.5 μm to 3.8 μm. From the calculation of the contrast it has been grown that lattice parameter of the precipitates differs from that of matrix by 0.02 ÷ 0.05 Å. – Besides, in crystals with high Se concentration (9.1019cm−3) small particles with symmetrical field of

ISSN:0023-4753    

DOI:10.1002/crat.19790140206

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractOxidation of BaF2single‐crystals as a result of annealing in air in the temperature range 600° to 900 °C leads to mechanical strengthening. The process kinetics was investigated. It is shown that oxidation takes place in the bulk of crystals owing to oxygen diffusion by formation and growth of oxidation centres. These centres are precipitates of a BaO phase which were revealed by chemical etch

ISSN:0023-4753    

DOI:10.1002/crat.19790140207

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractElectromigration of113Sn in Cu was investigated by the isothermal method in the temperature range from 918 to 1042 °C using the thin layer boundary condition. Following Gilder and Lazarus the welding interface was marked by help of a181Hf‐layer. The pseudo activation energy, which is (1.87 ± 0.29) eV, agrees within the experimental errors with the activation energy of impurity diffusion. Because of the fluctuation of the individual values a significant temperature dependence of the apparent effective charge could not been observed. The average value of the apparent effective chargez eff*= −33 ± 2. The residual resistance due to electron scattering at the jumping atoms yields for the models of Fiks, Huntington, Bosvieux and Friedel (3.4 ± 0.3)μ Ω cm/at%, (6.8 ± 0.6) μΩ/at% and (5.7 ± 0.6) μΩ cm/

ISSN:0023-4753    

DOI:10.1002/crat.19790140208

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractA disadvantage of the quantitative X‐ray diffraction analysis of samples from sheet metals is the incorrectness of the measuring results owing to the presence of textures in the material. In considering several reflexes of every phase the influence of textures may be reduced. Such a method will be presented and tested. The yielded results show that the new method can be useful for textured sheet metal sample

ISSN:0023-4753    

DOI:10.1002/crat.19790140209

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractX‐ray investigations of single crystals of 4′‐nitrophenyl‐4‐n‐octyloxybenzoate (NPOB) have been performed for the determination of the space group P21/c and the lattice constants (a0= 16.77 ± 0.02 Å,b0= 9.207 ± 0.005 Å,c0= 16.72 ± 0.01 Å, β = 128.0 ± 0.5°). Furthermore powder patterns after Debye‐Scherrer method have been taken to estimate thed‐values together with the indexing. On the basis of small Miller indices the crystal angles yielded a discrepancy between axis ratios determined from optical measurements and X‐ray methods. It can be shown that these differences appear wi

ISSN:0023-4753    

DOI:10.1002/crat.19790140210

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe relatively strong interaction between the surface of the glass and the nematic liquid crystals is demonstrated. The same texture of liquid crystals is observed after every renewed cycle of warming and cooling. Defects, which are invisible without an electrical field, become visible by the dynamic scattering effect. The thermografic results, which are received by cholesteric liquid crystals, are able to demonstrate only strong defects.

ISSN:0023-4753    

DOI:10.1002/crat.19790140211

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY