Research project SU/02 (Research action SU)
Coordinator: Prof. R. DELTOUR
1. Objectives
The aim of the project is to make bulk materials, single crystals, and thin and thick films of high-Tc superconducting materials presenting useful properties with a view to practical applications which are technically and economically feasible. This inter-university collaboration groups seven laboratories specialised in solid state physics,ceramics chemistry, materials engineering and electronics, and having extensive
experience in the fields of superconductivity, surface sciences, ceramic materials and electronic instrumentation.
The participants will systematically study intrinsic and extrinsic defects and their role in determining the superconducting properties of the materials. Such defects are induced by the different chemical constituents, the magnetic or non-magnetic dopants (impurities), the preparation methods, the microstructure. Control of these defects will be essential in producing superconducting materials with high critical current density values and in developing various practical applications.
During the first phase of the project (the first two years), the effects of composition, doping and preparation methods will be studied and characterised in situ by detailed microscopic analysis, principally on the YBaCuO and BiCaSrCuO systems. Other new HiTc compounds could also be investigated, depending on international progress and on the group's original work in the field.
Interactions between substrate, possible buffer layers, and superconducting films will be studied by various interface analysis techniques and correlated with more global superconducting equilibrium and transport properties.
With a mind to future technological and industrial developments, further extensive research will focus on the surface treatment of films by laser-induced recrystallisation under various atmospheres and/or by depositing coating layers, and on the interaction between films and low-resistance electrical contact electrodes.
In addition to their potential for industrial applications, these investigations of the role of impurities will provide important information which will shed light on the mechanism responsible for high-temperature superconductivity.
At the end of the first phase of the project, the progress made and the results obtained by the participating laboratories will be globally evaluated in the light of results published in the international literature. Accordingly, the participants may decide to reorient some of the research efforts. During the second phase of the project, the programme will continue along the (possibly reoriented) lines described above while, on the basis of the results obtained, a number of specific applications will be developed in the areas of microelectronics, telecommunications and/or electrotechnics.
2. Coordinated research programme
A. Synthesis and characterisation of powders (essentially YBaCuO and BiCaSrCuO) and of polycrystalline substrates :
1. solid-state reactions at high temperatures ;
2. wet chemical routes (sol-gel methods) and coprecipitation;
3. spray-drying of suspensions or solutions (aerosols) ;
4. study of the thermal processing of powders or of their precursors;
5. physical and chemical characterisation of superconductor powders :
. morphology;
. particle size distribution;
. chemical analysis.
B. Study of the sintering process :
1. cold-pressed pellets, thin and thick films ;
2. uniaxial and/or isostatic hot pressing under various atmospheres.
(Production of targets for research line E)
C. Production of thick films : screen printing.
D. Single crystal preparation by flux methods.
E. Production of thin films :
1. magnetron sputtering from multiple targets under an oxidising atmosphere ;
2. laser ablation.
F. Film treatment :
1. laser annealing under various atmospheres
2. possibly, coating with protective layers.
G. Physical-chemical characterisation (microstructure, defects, stoichiometry) of films and sintered bulk materials :
1. scanning electron microscopy ;
2. EDAX microanalysis;
3. thermogravimetry and differential thermogravimetry;
4. Auger and photoemission spectroscopy;
5. low-energy electron diffraction;
6. X-ray diffraction ;
7. analytical chemical methods;
8. micro-Raman spectroscopy;
9. FTIR spectroscopy.
H. Characterisation and studies of the electrical and magnetic properties of films, single crystals and bulk materials (temperature and magnetic field dependence) :
1. dc, ac (low and medium frequency) measurements;
2. low magnetic field susceptometry and high-field magnetisation measurements;
3. critical current measurements ;
4. room and low-temperature scanning tunnelling microscopy;
5. high-frequency electrical measurements.
I. Characterisation and studies of the thermal and thermoelectric properties of films, single crystals and bulk materials :
1. equilibrium properties
2. specific heat ;
3. transport properties, thermal conductivity, thermoelectric effects.
J. Theoretical interpretation and analysis of the results, simulation of dissipation phenomena (percolation, pinning forces and vortex motion, critical state).
K. Potential applications :
1. high current limitors ;
2. gate and interconnection lines for integrated circuits;
3. low-frequency magnetic screening;
4. SQUIDs ;
5. microwave cavities
