MgB2 THICK FILMS OBTAINED BY ELECTROPHORESIS TECHNIQUE: SYNTHESIS, STRUCTURAL AND SUPERCONDUCTIVE CHARACTERIZATION

Valeria Dellaroca 2Renato S. Gonnelli 2,4Silvia Bodoardo 3Nerino Penazzi 3Gianluca Grenci 3Chiara Portesi 5Mauro Rajteri 5Andrzej J. Morawski 1Tomasz Lada 1

1. Polish Academy of Sciences, High Pressure Research Center (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland
2. INFM and Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy
3. Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy
4. LAMIA-INFM, Genova, Corso Perrone 24, Genova 16125, Italy
5. Istituto Elettrotecnico Nazionale "Galileo Ferraris" (IEN), Strada delle Cacce, 91, Torino 10135, Italy

Abstract

MgB2 is a material known for several years, but only recently discovered as superconductive at about 40 K. MgB2 has a simple crystal structure with alternation of boron and magnesium layers, both in hexagonal array. It has mechanical strength and durability higher than superconducting oxides, weak-link-free grain boundaries, high transport critical current density (Jc),coherence length (>5 nm)higher than superconducting cuprates, low-cost starting materials and, above all, a transition temperature accessible to single stage cryocooler. Thanks to these properties, many efforts were done in order to synthesize MgB2 for large-scale applications, in form of bulk, wires, tapes and films.
In this contribution, we present the results on the preparation and the characterization of MgB2 thick films supported on Ti/Al2O3 and MoBN substrates via electrophoretic deposition technique (EPD).
We prepared superconducting MgB2 thick films by following two different routes: i) deposition of MgB2 powder, both pure and SiC doped, followed by a sintering step at high temperature and high Ar pressure in a furnace; ii) deposition of boron films and successive annealing in saturated Mg atmosphere at high Ar pressure.
The EPD deposition occurs at the anode of the electrochemical cell under an electric field of about 180 V/cm. The obtained films are homogeneous and well adhesive to the substrate. The MgB2 films were then sintered at 1200 K in inert atmosphere, whereas the boron precursors were reacted with Mg at temperature over 1500 K and at high pressure of 1 GPa. X-ray diffraction confirmed the formation of a crystalline MgB2 phase with hexagonal P6/mmm symmetry in the case of both MgB2 and B precursors.
The electrical properties of the samples were measured in liquid helium vapour, by using an AC-bridge with the standard four-probes technique and indium contacts. The samples obtained from MgB2 powder show high Tc of superconducting transition close to 35 K.

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Presentation: oral at E-MRS Fall Meeting 2004, Symposium E, by Valeria Dellaroca
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-05-01 11:33
Revised:   2009-06-08 12:55
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