| | 1 | Author
| Strontiumchromate, K. Hartl, R. Braungart | Requires cookie* | | | Title
| eine Hochtemperaturphase mit Defekt-Bariumphosphat-Struktur a High- Temperature Compound with Defect-Bariumphosphate Structure  | | | | Abstract
| Black hexagonal platelets growing on stron-tiumoxide in the presence of chromium (III)-oxide and air at temperatures from 1250 to 1400 °C have been shown to belong to the rhombohedral space group R3m. In hexagonal orientation the elementary cell has the axes ao = 1115.8 i 0.9 pm and c0 = 4037 ± 3,6 pm and Z = 24, Dx — 4.26. Structurally the compound is closely related to Ba3(P04)2, with the excep-tion, that there are defects in the metal sub-lattice. At temperatures below 1200 °C Stron-tiumchromate(V, VI) decomposes into the dis-crete chromates(V) and -(VI). At temperatures from 113 to 338 K the compound is an electronic semiconductor with an activation energy of 0.26 eV. | | | |
Reference
| Z. Naturforsch. 33b, 952—953 (1978); eingegangen am 1. Juni 1978 | | | |
Published
| 1978 | | | |
Keywords
| High-Temperature Oxochromate, Defect Structure, Mixed-Valence Oxochromate, Semiconductor | | | |
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| default:Reihe_B/33/ZNB-1978-33b-0952_n.pdf | | | | Identifier
| ZNB-1978-33b-0952_n | | | | Volume
| 33 | |
| 2 | Author
| Eberhard Krämer, Reginald Gruehn | Requires cookie* | | | Title
| Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen, VI* Präparative und strukturelle Untersuchung von WNb15O40F und nahe benachbarten Defektstrukturen im System Nb205-W03-Nb02F Contributions to the Study of Inorganic Non-Stoichiometrie Compounds, VI* Preparative and Structural Investigations of WNb15O40F and Closely Related Defect Structures in the System Nb205-W03-Nb02F | | | | Abstract
| In the quaternary system H-Nb20s-W03-Nb02F the phase WNbi504oF was prepared in form of light-yellow needles. The compound crystallizes in the monoclinic system with the unit cell dimensions a = 22.254 A, b = 3.829 A, c = 20.298 A and ß= 114.29°, space group C 2. Electron optical investigations showed the crystal structure containing 5 x 3 x co-blocks of Nb-(0, F)-octahedra, with metal atoms in tetrahedral positions located at the junctions of every four blocks. X-ray investigations showed a range of homogeneity between (O, F)/(W, Nb) = 2.556 <2.563 (WNbi5O40F) <2.571. The hypothetical phase WNbis047F2 with 6 x 3-blocks was found as a microdomain by electron microscopy. | | | |
Reference
| (Z. Naturforsch. 31b, 1569—1573 [1976]; eingegangen am 2. September 1976) | | | |
Published
| 1976 | | | |
Keywords
| System Nb20s-W03-Nb02F, Crystal Structures, Defect Structures, High Resolution Electron Microscopy | | | |
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| default:Reihe_B/31/ZNB-1976-31b-1569.pdf | | | | Identifier
| ZNB-1976-31b-1569 | | | | Volume
| 31 | |
| 3 | Author
| Hartmut Hibst, Reginald Gruehn | Requires cookie* | | | Title
| Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen, VII a Ein neuer einfacher Weg zur Berechnung von [(0,F)/Me]-Werten bei Blockstrukturen Contributions to the Study of Inorganic Non-Stoichiometric Compounds, VII a A New Simple Method to Calculate Values of [(0,F)/Me] for Block Structures | | | | Abstract
| A simple, quick and reliable method is derived to calculate values of [(0,F)/Me] for block structures. The method of calculation is exemplified using ideal and real (defect) block structures and inconsistent published data. The method represents a simple means to systematically classify block structures. | | | |
Reference
| Z. Naturforsch. 33b, 884—890 (1978); eingegangen am 13. Februar/12. Juni 1978 | | | |
Published
| 1978 | | | |
Keywords
| Block Structures, Crystal Structures, Defect Structures, High Resolution Electron Microscopy | | | |
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| default:Reihe_B/33/ZNB-1978-33b-0884.pdf | | | | Identifier
| ZNB-1978-33b-0884 | | | | Volume
| 33 | |
| 4 | Author
| Günter Heurung, Reginald Gruehn, Herbert Brunner | Requires cookie* | | | Title
| Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen, Villa Elektronenmikroskopischer Nachweis neuer, eng begrenzter Defekte bei Blockstrukturen und Berechnung ihrer O/Me-Werte Contributions to the Study of Inorganic Non-Stoichiometric Compounds, VIII a Electronmicroscopical Proof of New, Small Area Defects of Block Structures and Calculation of Their O/Me Values | | | | Abstract
| Compounds of the systems Fe203-Nb205 (O/Me < 2.5) and Nb205-W03 (O/Me > 2.5) were prepared by chemical transport. The block structures of the obtained phases were investigated by high resolution transmission electron microscopy. The unusual defects observed were nearly identical in both systems. A recently devel-oped method to calculate the O/Me value of block structures [ 1 ] was extended and used for these defects. | | | |
Reference
| Z. Naturforsch. 34b, 553—562 (1979); eingegangen am 27. November 1978 | | | |
Published
| 1979 | | | |
Keywords
| Block Structures, Crystal Structures, Defect Structures, High Resolution Electron Microscopy | | | |
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| default:Reihe_B/34/ZNB-1979-34b-0553.pdf | | | | Identifier
| ZNB-1979-34b-0553 | | | | Volume
| 34 | |
| 5 | Author
| C. Gebhardt, H. Gruler, E. Sackmann | Requires cookie* | | | Title
| O n Domain Structure and Local Curvature in Lipid Bilayers and Biological Membranes | | | | Abstract
| The lateral lipid organization and the local surface curvature in small and giant bilayer vesicles of binary lipid mixtures were investigated. Mixtures of the following lipids are studied: Cholesterin, di-alcyl-lecithins, dioleyl-lecithin and di-alcyl-phosphatidic acid. The latter is con sidered as being representative of charged natural lipids (e.g. phosphatidyl serine or cardiolipin). Three different experimental methods are compared: 1) The excimerfluorescence method, 2) the spin label technique and 3) the freeze fracture electron microscopy. The latter two methods yield information on the size of lipid precipitations. The surface curvature may be studied by electron microscopy. The essential experimental results are: (1) Mixtures of smectic phases of different symmetry undergo lateral phase separation. (2) The phase separation leads to a domain-like lateral lipid organization. (3) The domain structure is often accompanied by a variation in local curvature. (4) In membranes containing a charged lipid component, the domain structure may also be triggered by external charges (such as surface proteins). (5) two types of domains are observed: Circular domains (diameters of the order of several 100 A) occur in mixtures of non-tilted fluid and rigid phases. Elongated domains (width ~ 1 0 0 Ä) are observed in mixtures of tilted and non tilted phases. This domain pattern is characteristic for mixtures of lecithins and cholesterols. The domain structure is explained by combining the theory of spinodal decomposition of alloys with the essential result of the orientational elastic model of membranes. The domain size calculated from this model agrees well with the experimental result. The periodic ripple structure observed be tween the pre-and the main transition is explained by generalizing the concept of spinodal decomposi tion to include the separation of phases which are only distinguishable (e. g. by the tilt angle). The width of the domains in equilibrium is explained in terms of the spontaneous curvature of the decoupled monolayer of a bilayer. Good agreement with the experimental result is obtained. The ripple phase is only a special case of the surface induced domain structures in ordinary liquid crystals. The defect structure of the ripple phase has been analysed in terms of its symmetry. A symmetry rule is established which leads to a model of lipid orientation. Below the pretransition no periodic domain pattern is observed under normal conditions. But upon cooling a bilayer very rapidly a defect structure reminiscent of a screw dislocation is ob served. This is expected for coupled biaxial monolayers. | | | |
Reference
| (Z. Naturforsch. 32c, 581 [1977]; received December 8 1976) | | | |
Published
| 1977 | | | |
Keywords
| Model Membrane, Liquid Crystal Phase Separation, Curvature Elasticity, Defect Structure | | | |
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| default:Reihe_C/32/ZNC-1977-32c-0581.pdf | | | | Identifier
| ZNC-1977-32c-0581 | | | | Volume
| 32 | |
| 6 | Author
| Shao-Yi Wu, Wen-Chen Zheng | Requires cookie* | | | Title
| Defect Structure of Co 2+ Center in 05-LiIO 3 Crystal | | | | Abstract
| In this paper we establish the formulas of EPR g factors g», for 3d 7 ions in trigonal octahedral crys-tals from a cluster approach. In these formulas, the contributions from configuration interaction-and covalency-effects are considered. The parameters related to both effects can be determined from the optical spectra and the structural parameters of the studied crystal. With these formulas, the defect struc-ture of a Co 2+ center in a-LiI0 3 crystal is studied. It is found that, to reach good fits between the cal-culated and observed g», g ± , the O ions between Co 2+ and Li + vacancy (V Li) should shift away from the V u by about 0.49 A. "Hie displacement direction is consistent with those obtained for Cr 3+ , Fe 3+ , and Mn 2 centers in a-LiI0 3 crystals as well as with the expectation based on the electrostatic interac-tion model. | | | |
Reference
| Z. Naturforsch. 55a, 828—832 (2000); received June 29 2000 | | | |
Published
| 2000 | | | |
Keywords
| Electron Paramagnetic Resonance (EPR), Crystal-field Theory, Defect Structure, Co 2+, a-LiI0 3 Crystal | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0828.pdf | | | | Identifier
| ZNA-2000-55a-0828 | | | | Volume
| 55 | |
| 7 | Author
| W. Ua, Wen-Chen Zhenga | Requires cookie* | | | Title
| Local Lattice Distortion near Co2+ in SrLaA104 Crystal | | | | Abstract
| The local tetragonal distortion in the vicinity of substitutional Co2+ impurities in SrLaA104 crystal is studied by fitting the calculated EPR parameters g\\, g±, A\\ and A± to the observed values. The result shows that the local distortion is mainly due to the elongation of metal-ligand distance R± perpendicular to the C 4 axis. This point is consistent with the expectation based on the consideration of ionic radius sum. This smaller tetragonal distortion of the oxygen octahedron surrounding the Co2+ impurity than that in the host crystal is supported by the result obtained in Cr3+-doped SrLaA104 crystal. -P a cs: 61.70Rj; 76.30Fc; 71.70Ch | | | |
Reference
| Z. Naturforsch. 56a, 557—560 (2001); received May 11 2001 | | | |
Published
| 2001 | | | |
Keywords
| Defect structure, Electronic Paramagnetic Resonance (EPR), Crystal Field Theory, SrLaA104 Crystal, Co2+ Ion | | | |
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| default:Reihe_A/56/ZNA-2001-56a-0557.pdf | | | | Identifier
| ZNA-2001-56a-0557 | | | | Volume
| 56 | |
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