Superconducting MgB₂ films prepared by the Aerosol Deposition Method

Titelangaben

Denneler, Stefan ; Glosse, Philipp ; Oomen, Marijn ; Berthold, Thomas ; Stöcker, Thomas ; Hanft, Dominik ; Moos, Ralf ; Holzapfel, Bernhard ; Häßler, Wolfgang ; Weiss, Maximilian ; Weis, Frederik:
Superconducting MgB₂ films prepared by the Aerosol Deposition Method.
2016
Veranstaltung: The 7th Tsukuba International Coating Symposium , 08.-09. Dez. 2016 , Tsukuba, Japan.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Vortrag )

Weitere URLs

Abstract

Securing future electrical power demand in the world, high efficient power generation and distribution is needed. Large scale offshore wind turbines in the range > 6MW arranged to large wind parks are one of the promising candidates for environmental friendly power generation. In order to improve power rating, light weight structures and generators with increased power to weight ratios are needed. Thus new technologies enabling compact and light generator designs are required. Magnesium diboride (MgB₂) is one promising superconductor with working temperatures below 39 K and a low density of 2.57 g/cm³. Several techniques are known to prepare MgB₂ films, filaments or wires. The powder-in-tube technique is used commercially to produce multifilament conductors from in situ or ex situ prepared MgB₂ powders. Physical vapor deposition is appropriate to coat substrates with thin MgB₂ films. The Aerosol Deposition (AD) method is a spray-coating technique at room temperature used to produce films of brittle materials, mostly ceramics e.g. Al2O3. Due to its ceramic-like mechanical properties, polycrystalline films of MgB₂ can be deposited with this technique, as it was reported by Akedo, Hirose et al. and Sinha et al.. A defined aerosol of powder and a carrier gas is accelerated into a vacuum chamber. As soon as the particles collide with the substrate, they crack and a fine-grained film forms. AD promises cost effective thick films that are dense and nanocrystalline, applicable on various substrates.

In this study MgB₂ fine powders from different suppliers were used as starting powders to form films by ADM on substrates like glass and nickel base alloys. The film thickness of the first samples was about 5 μm. The influence of aerosol parameters like carrier gas type, gas flow and aerosol concentration is evaluated based on the quality of the deposited MgB₂ films. As reference, pellets of the raw materials were fabricated and thermally treated as well. Electrical characterization of as deposited layers show reduced superconducting properties like transmission temperature (Tc) and low current densities (jc). SEM and TEM analysis showed oxidized microstructures in the as deposited layers.