High temperature Ho₂O₃–ZrO₂ insulation coatings on AgMg sheathed Bi-2212 superconducting tapes by sol–gel technique for magnet technology

摘要

High temperature 0, 5, 8 and 12 mol % Ho₂O₃–ZrO₂ insulation coatings were successfully deposited on Ag and AgMg/Bi-2212 superconducting tapes using sol–gel technique for magnet technologies. With this purpose, transparent solutions were prepared from Ho and Zr-based precursor materials and then Ho₂O₃ effect on thermal, structural and microstructural properties were observed and discussed in the present study. It was found that Ho₂O₃ additive has a propensity to generate tetragonal ZrO₂ and help to stabilize it. It was observed that insulation coatings with a mosaic structure having cracks were fully compatible with Ag/AgMg sheathed Bi-2212 tape substrates because of oxygen permeability, high and low actual temperatures and W&R process in comparison with the conventional insulation process. In addition, surface roughness decreased with increasing Ho₂O₃ content, thereby decreasing the grain size. Although porosity values vary considerably from one porosity mesurement expression to another, porosities of the insulation coatings can be estimated to be in the range of 3 and 30 vol %.