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  • 1
    Electronic Resource
    Electronic Resource
    Application of High Resolution Powder Diffractometry to the Investigation of Structural Phase Transitions (1986)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 9 (Jan. 1986), p. 57-68 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/21/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.9.57.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Energy calculations for the lattice dynamics of NH4IO3 (1974)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 30 (1974), S. 518-521 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The lattice dynamics of ammonium iodate have been studied experimentally and theoretically for centre-zone phonons. The frequencies of normal modes have been measured by Raman spectroscopy. The experimental results have been used to obtain the parameters of a simplified rigid-ion model. It is shown that the strongest bonds are the linear I-O and N-H covalent interactions, while the low-frequency external NH4-IO6 mode is mainly ionic in character. The effective ionic charge of the NH4 group is - 0.82 e.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739474001240
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal contraction in NH4IO3 and its significance with respect to the phase transition (1975)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 810-813 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: NH4IO3 shows an abrupt contraction in the direction of spontaneous polarization at 82°C. This anomaly is accompanied by changes in the optical properties and phonon spectra, which were also studied at different pressures. On the basis of the lattice parameters and Raman spectra a probable mechanism is suggested for the phase transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S056773947500174X
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  • 4
    Electronic Resource
    Electronic Resource
    Ferroelastic phase transitions in lead phosphate–vanadate Pb3(PxV1−xO4)2 (1977)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 33 (1977), S. 399-408 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The 'pure' ferroelastic behaviour of P-rich Pb3(PxV1 - xO4)2 is of the improper type. The ferroelastic phase transition is antiferrodistortive and accompanied by a second one at a lower temperature. The temperature range of the intermediate phase is approximately 20°C. At the transition points singularities of phonon spectra, dielectric and optical behaviour, and lattice constants are found. The Raman frequencies, the infrared absorption and reflexion spectra are given and interpreted on the basis of a mechanical and a rigid-ion lattice-dynamical model. From the results a critical mode is predicted at the boundary of the Brillouin zone (L in R{\bar 3}m). Further, the Γ phonon becomes weak at the lower transition point. The normal coordinates of both modes give parallel and antiparallel deviations of Pb positions from the [111] axis of the rhombohedral R{\bar 3}m high-temperature phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739477001065
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  • 5
    Electronic Resource
    Electronic Resource
    Ferroelastic phases in Pb3(PO4)2–Pb3(AsO4)2; X-ray and optical experiments (1981)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 145-153 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Mixed crystals Pb3(PO4)2--Pb3(AsO4)2 are ferroelastic at low temperatures. The phase diagram contains three different phases a (paraelastic), \tt b and \tt c (both ferroelastic). The transformation \tt a-\tt b is first order for Pb3(PO4)2 and approaches second-order behaviour with increasing As content. The spontaneous strains and the birefringence follow approximately a Curie-Weiss law, with a corresponding order-parameter exponent β = ¼. The mutual high-temperature phases give diffuse X-ray reflections due to inelastic scattering. The soft-mode model is discussed for these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739481000417
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  • 6
    Electronic Resource
    Electronic Resource
    Symmetry and lattice dynamics of oxides with perovskite-like structures (1976)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 32 (1976), S. 233-238 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Based on a topological definition the possible space groups for a perovskite-like structure are derived for small unit cells. The irreducible representations are calculated from them for interpretation of the phonon spectra. To compare the character of the bonds in some oxides, Raman spectra have been taken and interpreted on the basis of a simple lattice-dynamical model. It was found that covalent interaction occurs in NaxWO3 and XIO3 (X = NH4, K, Rb, Cs) whereas titanates and niobates are mainly ionic. A model for classification of perovskite-like compounds is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739476000521
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  • 7
    Electronic Resource
    Electronic Resource
    Crystal structure and charge carrier behaviour of (W12.64Mo1.36)O41 and its significance to other related compounds (1981)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 449-456 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of (W12.64Mo1.36)O41, containing {102} crystallographic shear (CS) planes, has been solved, a = 23.939 (9), b = 3.966 (1), c = 16.729 (15) Å, β = 106.74 (5)°; P2/c; R = 0.10 for 1285 reflections. It was shown that the Mo atoms segregate on positions in the CS planes. The O atom octahedra are distorted in typical arrangements, so that the elastic strain energy could be estimated. The hypothetical phases (W,Mo)nO3n - 1 for a wide range of values of n were derived from the experimental atomic parameters. Optical and electrical experiments show the existence of two types of charge carriers, a minority in the interplanar material, which contribute to conductivity, and a majority of trapped positions in the CS planes, preferentially on Mo positions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739481001101
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  • 8
    Electronic Resource
    Electronic Resource
    Physical properties and phase transitions in WO3 (1975)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 356-359 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A study of the phase transitions in WO3 crystals by Raman and absorption spectroscopy reveals that WO3 possesses two stable (or metastable) modifications at room temperature, differing slightly but definitely in their physical properties. Measurements of electrical conductivity show that both are insulators at low temperatures and semiconductors at higher temperatures. One is monoclinic and the other triclinic. Both exhibit at lower temperatures discontinuities in their physical properties without accompanying changes in cell parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739475000745
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  • 9
    Electronic Resource
    Electronic Resource
    Lattice dynamics of WO3 (1975)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 360-363 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The Raman spectrum of WO3 has been investigated from -180 to 290°C. An interpretation of the phonon spectra of the phases with higher symmetries is carried out by group theory. The normal coordinates of tetragonal WO3 have been calculated and a correlation of the phase transitions with the critical behaviour of some of the normal modes has been attempted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739475000757
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of twins on critical currents of high Tc superconductors
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 162-164 (1989), S. 1605-1606 
    Details
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-4534(89)90844-7
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