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

Abstract

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.