Gent University (Universiteit Gent)
Department of Inorganic and Physical Chemistry Research Group on Solid State Chemistry and Ceramic Superconductors
- Main Activity: Solid state chemistry of ceramic superconductors
- Description: The webpage listed below does not contain any details of the superconductivity-related research, which are as follows:
- The research group has activities in the broad field of solid state chemistry related to the synthesis, properties and applications of inorganic and ceramic materials.
Prof.dr. Serge Hoste, Prof. dr. I. Van Driessche, Dr. E. Bruneel, Drs. Veerle Cloet, Drs. Klaartje De Buysser, Drs. Tran Thi Thuy, research students: Nigel Vandevelde, Pieter Vermeir, Jonas Feys, Bart Vandeputte, Iwein Cardinael, Tatiana Amanova, . Major cooperations are developed with Slovak Academy of Sciences, U. Dresden, Forschungszentrum Karlsruhe and University of Cambridge. Our main interests is the establishment of the relationship between synthesis route via solid state reaction, spray drying, sol-gel chemistry, spray pyrolysis, flame spraying, etc. and the properties and phase purity of the resultant ceramic and composite materials. Therefore, the synthesis process is monitored using a variety of microscopic and analytical tools such as thermal decomposition studies, thermo-microscopy, dilatometry, SEM, TEM, XRD, UV-VIS and AAS. These techniques are used to study the synthesis of new and smart materials such as CeO2 thin films, high temperature superconductors, Bi-Molybdate catalysts, tungstates with negative thermal expansion coefficient, paramagnetic coordination complexes, and metal-ceramic composites.
- Subjects related to superconducting materials:
- Synthesis and characterisation of superconducting solids of the family YBCO, NdBCO, BSCCO, HgBCCO.
- Deposition of thick ceramic coatings using acethylene flame spray pyrolysis for the construction and reconstruction of magnetron targets for superconducting coatings.
- Fabrication of coated conductors based on aqueous precursors. This is the area in which the largest effort in made nowadays. The basic idea of this economically very attractive alternative to vacuum-based methods, is to develop a procedure for the deposition of buffer layers and superconducting layers, based on YBCO, starting from aqueous solutions in which the different components are dissolved on an atomic or molecular scale. Those solutions can easily be deposited in ambient atmosphere (e.g. by dip coating) on a variety of substrates (mostly SrTiO3 single crystals and textured Ni-W tape). The research focuses on two aspects: a) the composition of the solution is based on the presence of any combination of metal ions and a concomitant quantity of complexing agent which has to fulfil two tasks. In the first place, the complexant allow us to maintain a rather high quantity of ionic metal species (compared to an aqueous solution of their salts) thereby avoiding unwanted hydrolysis to metal-oxides of hydroxides and b) the complexant needs to possess several functional groups (-OH, -COOH, -NH2...) that result in cross condensation and the formation of a rather stable 3D-network gel that precludes the growth of crystals as long as the temperature is below the thermodynamic formation temperature of the correct phases. Fine tuning of such a system requires the following input and availability of practical facilities: a) measurement of thermodynamic constants of formation of the many different metal complexes formed and their dependence on pH, overall concentration and temperature, b) structural information in the gel state to be obtained by spectroscopic methods such as IR, UV, EXAFS, c) dust free continuous dip coating facilities. The tapes produced are characterized in their magnetic, electric, morphologic and chemical properties using standard methodologies such as thermal analysis, all forms of optical and electron-microscopy, XPS, Jc and Tc measurement by transport and induction.
Results obtained so far have yielded a useable aqueous system for the deposition of biaxially aligned CeO2 buffer layers on SrTiO3 and textured Ni/W and a combination of acetates, ethanolates, citrates and EDTA for the deposition of strongly biaxially textured YBCO and NBCO on SrTiO3 with acceptable Tc and Jc (0,3MA/cm). Further developments are oriented towards the improvement of the oxygen content at the HTSC-substrate interface, the assessment of deleterious carbonaceous materials at grain boundaries, the development of aqueous techniques for deposition of multilayers and the formulation of other types of buffers such as LaZrO3 and the incorporation of multimetal-nanopowders in our coatings.
- Recent publications
“A water based sol-gel technique for chemical solution deposition of (RE)Ba2Cu3O7-y (RE = Nd & Y) superconducting thin films”.
B. Schoofs et al.,
Supercond. Sci. Technol. 2007
accepted for publication.
“Non vacuum deposition techniques for
superconductor ceramic coatings”.
Van Driessche, G. Penneman, E. Bruneel, S. Hoste,
Pure and Applied chemistry, 74:11 (2005) 2039-2046
“Accurate determination of the composition of
Y-Ba-Cu-O superconductor by spectrophotometry,
gravimetry and flame AAS” Source
Supercond. Sci. Technol. 18:6 (2005 ) 907-911
“Chemical approach to the deposition of textured CeO2 buffer layers based on sol gel dip coating”,
Van Driessche, G. Penneman, J.S. Abell,
E. Bruneel, S. Hoste,
Materials Science Forum 426: 4 (2003), 3517-3522.
“Encapsulations Through the Sol-Gel Technique and their Applications in Functional Coating”
Van Driessche I. and Hoste S. in
Functional Coatings S. Kumar Gosh Ed.,
Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2006
“Characterisation of the sol-gel process in the
superconducting NdBa2Cu3O7-y system”,
B. Schoofs, D. Van de Vyver, S. Hoste, G. Herman
and I. Van Driessche,
Chemistry of Materials, 2006, accepted for publication.
- Prof. Dr. Serge Hoste
Fax : +32/9.264.49.83
- Prof. Dr. Isabel Vandriessche
Department of Inorganic and Physical Chemistry
Faculty of sciences
Krijgslaan 281 (S-3)