MgB2 superconducting films on Hastelloy prepared by Aerosol Deposition Method

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Kauffmann-Weiss, Sandra ; Häßler, Wolfgang ; Günther, Elisabeth ; Scheiter, Juliane ; Denneler, Stefan ; Glosse, Philipp ; Berthold, Thomas ; Oomen, Marijn ; Arndt, Tabea ; Stöcker, Thomas ; Moos, Ralf ; Weiss, Maximilian ; Weis, Frederik ; Holzapfel, Bernhard:
MgB2 superconducting films on Hastelloy prepared by Aerosol Deposition Method.
2016
Event: Applied Superconductivity Conference 2016, ASC2016 , 04.-09.09.2016 , Denver, Colorado, USA.
(Conference item: Conference , Speech )

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Since the discovery of superconductivity in MgB2, various preparation methods have been developed for films, filaments, or wires of this material. Multifilament conductors are prepared with the powder-in-tube technique using in-situ and/or ex-situ reacted MgB2 powders. Within this method, powders are packed inside a metallic tube, which is directly cold worked into long conductors and annealed afterwards at high temperatures. The complexity is adapted to the needs of targeted applications. Another possibility is the Mg diffusion method where different Mg and B precursors undergo a reaction. A third possibility is physical vapor deposition; however this method requires a well-adjusted atmosphere and the prevention of oxygen contamination. A new method for preparing films is using pre-reacted MgB2 powder by the technique called Aerosol Deposition Method (ADM) which is known for preparation of ceramic films. ADM is a spray coating technique to produce dense and nanocrystalline films at room temperature directly from a powder on the substrate. During particle collision and the impact on the substrate, a portion of the kinetic energy is converted into bonding energy. Hence, particles can be compressed in-situ during the impact. This opens up a new method to manufacture coated conductors. We will demonstrate the versatility of this new method for MgB2 films. First experiments show thick superconducting MgB2 films on oriented Al2O3 substrates as well as on Hastelloy substrates. The as-deposited films show a superconducting transition between TC0 = 18 K and TC100 = 36K. An increased critical temperature with a smaller width of transition can be observed after an additional thermal treatment at low temperatures. Besides, transport JC values were determined by the standard four probe method using the 1μV/cm electric field criterion. So far, it had not been possible to produce technically MgB2 tapes at lower temperatures. Thus, the aerosol deposition at room temperature combined with high deposition rates of 1μm/10min would enable a promising route towards a technical realization of long tapes.