Fabrication of new high temperature Gd₂O₃-ZrO₂ insulation coatings on Ag tapes by sol-gel technique for magnet technology

Cost-effective and easy-to-apply materials are necessary for magnet technologies. This research covers a fabrication development of high temperature insulation coatings for magnet technologies. With this context, gel coatings were successfully deposited on Ag tapes using sol-gel technique by preparing transparent solutions from Gd- and Zr-based precursor materials, methanol and glacial acetic acid, and subsequently 0, 5, 8, and 12 mol% Gd₂O₃-ZrO₂ coatings were heat treated at 300, 500, and 800 °C which respectively indicate drying, heat treatment, and annealing processes. Prior to coating process, Gd₂O₃ effect on thermal, structural and microstructural, and electrical properties were observed and extensively discussed in the present study. FTIR revealed that when increasing heat treatment temperature from 25 to 800 °C, the frequencies of O-H, C-H, and C=O bands decreased. According to XRD results, Gd₂O₃ additive has a propensity to generate tetragonal ZrO₂ and help to stabilize it. It was also observed that the regular surface morphology generally forms when Gd₂O₃ content increase in ZrO₂ from 0 to 12 mol%. The film thicknesses increased from 0.5 to 1.8 μm as a function of number of dipping. The porosities of the insulation coatings can be estimated to be in the range of 25 and 40 vol%. Besides, as insulative layers, Gd₂O₃ additive improved ZrO₂ coatings. As a result, commercial Ag and AgMg sheathed Bi-2212 long length tapes can be insulated with pure ZrO₂ and Gd₂O₃-ZrO₂ coatings and then the coated tapes can be wound to fabricate an electromagnet.