Zur Korrespondenz von Kristallstruktur und Habitus. Bestimmung der Molekülschwerpunkte in organischen Kristallen

Screw axes and glide planes lower the morphological importance of certain crystal faces. It has been demonstrated, that pseudosymmetry also influences crystal tracht. In case of organic crystals it is sometimes possible to determine the approximate molecule centres with aid of „morphological extinction tables”︁.     

Statistische Untersuchungen zum Wachstum und Habitus von Fluor-Amphibol-Kristallen in Oxid-Fluorid-Gemengen

The habit of fluor-richterite crystals growing in oxide-fluoride-mixtures is determined by the character and composition of melting phase developping in the mixtures. Firstly it depends on the nucleation rate of crystals growing within the melt. Factors governing habits are the contents of chlorine and fluorine respectively and the physical preparation of batches. Most fibrelike crystals grow in mixture containing 10% NaCl, which are heated in the interval between 950 and 1050°C.     

Zur Morphologie organischer Kristalle mit zwei Molekülen in der asymmetrischen Einheit. Ein Beitrag zur Korrespondenz von Kristallstruktur und Habitus

It has been demonstrated in an earlier publication, that pseudosymmetry influences crystal tracht of organic crystals. The morphological lattice of structures with two independent molecules in the unit cell corresponds with the lattice of the centers between the two molecules. This can be pointed out with aid of “morphological extinction rules”.     

Zur Diffusion von Hf und Ti in Ni

The diffusion coefficients and solubilities of Hf in Ni were measured with the electronprobe at sandwich samples. The temperature dependence of the diffusion coefficients of Hf in Ti was compared with the corresponding values of the system Ti in Ni. In both systems was found a good accordance with the Arrhenius relation within four orders of magnitude. The solubility of Hf in Ni is found to be nearly by the factor 2 larger than the values known from earlier papers.     

Zur Kristallographie von Doppelsalzen aus Calciumsulfat und Natriumsulfat

In the course of investigating a special slurry problem in the Na₂SO₄ production metastable double salts of calcium sulphate and sodium sulphate were detected (Emons, Stegmann). In this paper it is reported on the properties of these compounds and their decomposition products, determined by microscopic, X-ray, thermoanalytic, and IR-spectroscopic methods.     

Zur dynamischen Untersuchung elastischer und elektromechanischer Eigenschaften von Kristallen

For the determination of elastic and piezoelectric coefficients as well as of the mechanical quality factor the piezoelectric resonator has proved a most simple and exact method. In this paper some possibilities for increasing the accuracy of this method and its application on weak piezoelectric crystals as well as for the determination of higher order elastic coefficients are shown. These procedures can also be used for dynamic measurements on electrostrictive materials (electrostrictive resonator).     

Zur Gleichgewichts- und Wachstumsform von β-Kupferphthalocyanin-Einkristallen

The equilibrium shape of β-copper-phthalocyanine single crystals is obtained by the method of the PBC-vectors according to HARTMAN and PERDOK . These results agree well with the experimentally found growth shape of single crystals grown in the vapour phase. The crystals are of needle-like shape. The crystal surfaces are lattice planes of the kind {001}, {201 }, {100}, {101 } and {110}. The ratio of length to width of the crystals is influenced by the inert gas pressure during the growth process. This dependence is caused by the diffusion of the nutrient.     

Beeinflussung der elektrischen Eigenschaften von Vanadiumdioxid-Pulver durch Reduktionsbehandlung

A reducing technique for a definite setting of the electrical resistivity and the switching voltage of vanadium dioxide powder samples is described. The dependence of the electrical behaviour on the reducing temperature, the grain size and the phase contaminations is reported. Investigations by metallographic, X-ray, electrical, and magnetic methods have shown that the change of the electrical resistivity is caused by a reducing of the VO₂ grains decreasing to the center of the grains. The oxygen content reaches the oxygen deficient VO₂ phase boundary or less at the grain surface.     

Zur Bestimmung der Konzentration von Leerstellen und Versetzungen plastisch deformierter Metalle mittels Positronenannihilation

The use of positron annihilation to estimate the concentration of crystal defects is described and a model for the estimation of defect concentrations is given in case that more than one kind of defects are present. This model is based on the recovery of one kind of defects to another in steps. From angular correlation measurements of cold-worked and recovered Pd have been concluded that it is possible to distinguish between vacancies and dislocations in the experiment. Using a value of μ = 2 · 10¹⁵ s⁻¹ for the trapping rate per unit defect concentration, the data for 7.5% thickness reduction yields values in the expected order of magnitude for dislocation density and vacancy concentration. The study of the change of the angular correlation shape by plastic deformation shows that the narrowing of the angular correlation is caused by the reduction of both, indensity and width of the gaussian part which originates in annihilation with core electrons.     

Beeinflussung des spezifischen Widerstandes von sauerstoffreichen Silizium-Einkristallen durch Temperprozesse

Variations of the mean value of resistivity and its lateral distribution occurring in silicon after annealing near 450 °C are determined by the generation of donor active siliconoxygen complexes. The maximum value of additional donor concentration reached after annealing for more than 100 hours, goes with the 3. power of interstitial oxygen concentration. The experimental results are discussed in view of known models. Examples of the kinetics of thermal donor formation and annihilation are given at samples with inhomogeneously distributed oxygen content. A method with high lateral resolution in determining the distribution of oxygen is deduced and its sensitivity limits are estimated.     

Zur Bildung von Adsorptionsmischkristallen

By investigating the systems KCl-H₂O-impurity and NH₄Cl-H₂O-impurity the knowledge of the formation of Adsorptionsmischkristallen could be extended. Some specific properties of complex mixed systems are stated.     

Zur Abschätzung physikalischer und physikalisch-chemischer Daten von AlBV-Verbindungen mit Zinkblendestruktur

The AlB^V-compounds display an exceptional position among A^IIIB^V-compounds regarding some properties which are related to the lattice constant. This behaviour is connected with the absence of core-d-electrons in Al. The compressibilities of AlP, AlAs and AlSb can be estimated from the lattice constant and the microhardness in fair agreement with calculated values. Relations between the lattice constants, molecular weight, some band structure parameters, the heats of formation and the surface energies are discussed. Phillips' ionicity parameter of AlSb is corrected and the bowing parameter of the energy gap of mixed AlB^V-compounds is calculated from the difference of the atomic radii of the substitutes.     

Zur Lumineszenz von Zinksiliziumphosphid

Results of cathodoluminescene measurements of ZnSiP₂-single crystals grown by different techniques are reported. The luminescence excited in the various samples showed considerable differences in intensity and spectral position. These differences are apparently caused by the irregular incorporation of recombination centres in the present stage of crystal growth. Samples grown by “vapour phase technique with ZnCl₂” and by “spontaneous crystallisation from Sn or zn melt” showed line spectra typical for the special method of crystal growing. This relation between a typical line spectrum and the method of crystal growing chosen is attributed to the participation of intrinsic defects in the recombination processes. The detection of doping elements by means of luminescence measurements is discussed for ZnSiP₂ crystals doped by adding Te, Se, Ga. or In to the Zn melt.     

Zur Kristallzüchtung von Cadmiumsulfid und anderen II–VI-Verbindungen (III) Gleichgewichtsdrucke über den Sulfiden in Wasserstoff enthaltenden Gasen

Starting from the reaction formulas 2 MS_f = 2M + S₂ and H₂ + 1/2 S₂ = H₂S vapour pressures of Mg, Zn, Cd, Hg from their sulphides are calculated for various H₂ H₂S-inert gas mixtures and temperatures. They are discussed, compared with values from literature and transpiration experiments and evaluated for crystal growth.     

Zur Struktur von organischen Mischkristallschichten

The structure of organic mixed crystal films is investigated by means of a appropriated model - copper phthalocyanine/vanadyl phthalocyanine. These films are polycrystalline and contain mixed crystal grains, the size being smaller than that which can be detected by X-ray methods. By infrared spectroscopy and scanning electron microscopy or after recrystallisation by texture goniometer investigations the orientations of microcrystals on the substrate was obtained.