Effect of grain size on the electrical and magnetic properties of MgB2 thick films deposited on the Al2O3 single crystal substrates

Abstract

MgB2 films having thicknesses of approximately 10 μm have been prepared on the Al2O3 single crystal substrates by using ultrasonic spray pyrolysis technique. The films fabricated were then analyzed by means of microstructural, structural, transport and magnetic properties. The influence of grain size, depending on the ex-situ and in situ heating, were investigated. The results obtained showed that the size of MgB2 grains has an effect on the transport and magnetic properties of the films. Films prepared with in situ heating have small particle size (<50 nm) and were found to be much better properties than the films prepared ex-situ heating, which have larger grains (~1 μm). The best Tc value and critical current density, Jcmag, were obtained to be ~36 K and 9.88 × 105 A cm−2 respectively for the films prepared with small grains. The results were showed that the smaller grain size and in situ heating cycles are essential points for quality thick film MgB2 fabrication.