SVIBOR - Project code: 1-03-057

MINISTRY OF SCIENCE AND TECHNOLOGY

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Project code: 1-03-057


CORRELATED SUBSYSTEMS IN SUPERIONIC CONDUCTORS AND SEMICONDUCTORS


Main researcher: VUČIĆ, ZLATKO (53532)


Assistants
Type of research: basic
Duration from: 01/01/91. to 12/31/95.
Papers on project (total): 47
Papers on project quoted in Current Contents: 17
Institution name: Institut za fiziku, Zagreb (35)
Department/Institute: Semiconductor physics department
Address: Bijenička cesta 46, P. p. 304
City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (0)1 271 211
Fax: 385 (0)1 421 156
E-mail: vucic@olimp.irb.hr
Summary: The growth of two-component superionic conductors single crystals (nonstoichiometric cuprous selenide Cu2-xSe) under the thermodynamical equilibrium conditions and their characterization were the subject of research work. Preliminary the equilibrium shape single crystals up to 5 mm in diameter were obtained. The crystal facetting was monitored and the size measurements performed during the growth. The temperature dependent structural changes of quasi-1D CDW system of the new generation ((NbSe4)10I3) were investigated, in order to find structural background for the anomalous behaviour of its transport and thermal properties. The most prominent and reversible structural effect found below Peierls transition is symmetrically equivalent monoclinic splitting of tetragonal lattice. Basically related to a shearing mode along chains, it appears to be a direct consequence of interchain CDW interaction. The correlated subsystems in complex crystal structures were investigated by electron microscopy and electron diffraction on several types of high-temperature superconductors (metal doped copper oxides): Ca.85CuO2, (Sr/Ca).85CuO1.71, MSr2(RE)nCu2O5+2n; M=Ga,Co,Al or C,S,...; n=0,1,2,3. All cuprates investigated revealed two interpenetrated lattices-subsystems with various partial structures - chains, bands, loops, nets. Interactions within each subsystem result in formation of the particular sublattice of a different translation symmetry in common crystal structure. The mutual interactions of different subsystems produce either an incommensurate modulation of common crystal structure or a commensurate superstructure.

Keywords: equilibrium crystal shape, surface roughening, superionic conductors, mobile ion subsystem, short range order, quasi-onedimensional conductors, haloids of metal-tetrachalcogenoids, incommensurate-commensurate phase transition, cuprates, high-Tc superconductors, layer compounds, superstructures, substructures, modulated structures, electron microscopy and diffraction

Research goals: The investigation of superionic conductors is primarily aimed at better understanding of the type and range of ion-ion interaction within the mobile-ion subsystem, as well as of interactions between the two coexistent subsystems - mobile ions and the immobile cage lattice. The growth and morphological study of equilibrium shape single crystals is focussed on temperature and concentration dependence of facet types and size and critical behaviour of the shape of curved surface near a facet edge, reflecting the interactions in a crystal. The research on superconducting ceramics - cuprates should provide better understanding of the correlation between the superconductivity phenomena and the layered crystal structure, i. e. the number of Cu-O planes and the ordering in these planes.

COOPERATION - PROJECTS


  1. Name of project: B/CI1*-913183 Investigation of structural properties and phase transitions in anisotropic systems with incommensurately modulated structures
    Name of institution: Rijksuniversiteit Groningen Inorganic Laboratory Department of Chemistry Nyenborgh 16
    City: 9747 AG - Groningen, Netherlands

  2. Name of project: B/CI1*-913167 Structural properties of superionic conductors
    Name of institution: EMAT University of Antwerp (RUCA) Groenenborgerlaan 171
    City: B-2020 - Antwerpen, Belgium

  3. Name of project: SU*03*017 National impulse programme on high-Tc superconductivity
    Name of institution: EMAT University of Antwerp (RUCA) Groenenborgerlaan 171
    City: B-2020 - Antwerpen, Belgium

  4. Name of project: IUAP*11 Incentive program on high-Tc superconductors
    Name of institution: EMAT University of Antwerp (RUCA) Groenenborgerlaan 171
    City: B-2020 - Antwerpen, Belgium
Other information about the project.
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Last update: 10/10/95
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