SVIBOR - Project code: 1-07-166

MINISTRY OF SCIENCE AND TECHNOLOGY

Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
E-mail: ured@znanost.hr

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Project code: 1-07-166


SUPERCONDUCTING OXIDES AND METAL COMPLEXES


Main researcher: BRNIČEVIĆ, NEVENKA (5652)


Assistants
Type of research: basic
Duration from: 01/01/91. to 12/31/93.
Papers on project (total): 67
Papers on project quoted in Current Contents: 17
Institution name: Institut "Ruđer Bošković", Zagreb (98)
Department/Institute: DEPARTMENT OF CHEMISTRY/DIVISION OF PHYSICAL CHEMISTRY Complex Compounds Laboratory
Address: Bijenička 54, Zagreb
City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (0)1 4561-189
Fax: 385 (0)1 272-648
Fax: 385 (0)1 425-497
E-mail: basic@olimp.irb.hr
E-mail: brnicevic@olimp.irb.hr
Summary: Several systems of high-temperature superconducting oxides like: Bi-Ca-Sr-Cu-O, Hg-Ba-Ca-Cu-O, Sr-(Ln,Ce)-M-Cu-O, Ln=rare earth elements, M=Nb, Ta, Mo, W, Fe, have been studied. In order to prepare superconducting oxide phases with critical superconducting transition temperature close to the ambient conditions different mixtures of transition and earth-alkali metals with rare earth elements in different proportions are thermally treated. These investigations are related to the single phase and multiphase samples preparation and also include structural, spectroscopic, magnetic and electrical characterization. The reactions of the hexanuclear cluster units of the composition /M6X12/n+, M=Nb or Ta, X=Cl or Br, n=2,3,4 and /M6X8/m+, M=Mo,W, m=4,5,6, with aliphatic alcohols, hydroxide and alkoxide ions, and ligands containing nitrogen atom(s) as donor(s) have been investigated. Reactions of mononuclear complex species of niobium, tantalum, molybdenum, calcium and magnesium with hydroxy carboxylic, dicarboxylic and keto acids are investigated.

Keywords: superconducting oxides, high-temperature superconductivity, magnetic susceptibility, electron paramagnetic resonance, microwave absorption, metal clusters, metal complexes, polynuclear complexes, crystal structures, uric acid complexes

Research goals: Reproducible procedures for the preparation of single phase samples of the suitable magnetic and transport properties, with critical values such as temperature, electrical density and magnetic field high enough for technological application. New techniques for the preparation of single crystals of high-temperature superconducting oxides. Methods development for characterization of oxide superconductors from scientific and technological aspects with broadening our knowledge on the nature of superconducting state in the new superconductors. It is expected that the new chemical reactions betweencopper, bismuth, thallium, mercury, titanium or other transitionmetal elements with earth-alkali and rare earth metals as cationscould result with new, yet undiscovered material properties with critical superconducting transition temperature close to normal conditions. The hexanuclear halide clusters of niobium and tantalum are known in three different oxidation states, /M6X12/2+,3+,4+, M=Nb or Ta, X=Cl or Br. The hexanuclear clusters of molybdenum and tungsten are known as /M6X8/m+, M=Mo or W, m=4,5,6. Reversible oxidation-reduction processes are possible within these two groups of clusters without destroying a particular cluster unit. This indicates that these clusters could be suitable for the reversible multielectron redox (or photoredox) reactions that are interesting with respect to processes such as energy conversion, light-induced splitting of water molecules or catalytic redox reactions. For this purpose it is necessary to learn more on the nature of metal-metal and metal-ligand bonds in of each oxidation state separately. The experiments are designed in which these cluster compounds (so far known as isolators) could be transformed into metallic state.

COOPERATION - PROJECTS


  1. Name of project: JF 891 Cluster Systems of Niobium, Tantalum, Molybdenum & Tungsten
    Name of institution: Ames Laboratory, USDOE, and Department of Chemistry, Iowa State University
    City: 50011 - Ames, Iowa, USA

COOPERATION - INSTITUTIONS


  1. Name of institution: Institut fuer Angewandte und Technische Physik, Technische Universitaet Wien
    Type of institution: Economical/Production
    Type of cooperation: Joint publishing of scientific papers
    City: A-1040 - Wien, Austria

  2. Name of institution: Institut fuer Experimentalphysik, Technische Universitaet Wien
    Type of institution: Economical/Production
    Type of cooperation: Joint publishing of scientific papers
    City: A-1040 - Wien, Austria

  3. Name of institution: Institut fuer Experimentalphysik der Universitaet Graz
    Type of institution: Economical/Production
    Type of cooperation: Joint publishing of scientific papers
    City: A-8010 - Graz, Austria

  4. Name of institution: Walther-Meissner-Institut fuer Tieftemperaturforschung
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: W-8046 - Garching, Deutschland

  5. Name of institution: Max-Planck-Institut fuer FestKoerperforschung
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: W-7000 - Stuttgart, Deutschland

  6. Name of institution: Prirodoslovno-matematički fakultet Zagreb
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 10000 - Zagreb, Croatia

  7. Name of institution: Institut za fiziku Sveučilišta u Zagrebu
    Type of institution: Economical/Production
    Type of cooperation: Joint publishing of scientific papers
    City: 10000 - Zagreb, Croatia

  8. Name of institution: Klinička bolnica "Sestre milosrdnice"
    Type of institution: International organization
    City: 10000 - Zagreb, Croatia
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