Stress analysis of ceramic insulation coating on Cu/MgB2 wires for W&R MgB2 coils

Ceramic insulation coatings were produced on Cu/MgB2 wires, which were fabricated by Hyper Tech Research Inc., using Continuous Tube Forming and Filling (CTFF) process, from the solution of Zr, and Y based organometalic compounds, solvent and chelating agent using reel-to-reel sol–gel technique for MgB2 coils. Y2O3–ZrO2/Cu/MgB2 wires were annealed at 700 °C for 30 min with 5.8 °C/min heating rate under 4% H2–Ar gas flow. Residual stresses were examined for Cu/MgB2 wire and YSZ coatings with varying thicknesses. It was observed that displacement values are independent from YSZ thicknesses and the maximum effective stress value is in the Cu region. The surface morphologies and microstructure of samples were characterized using SEM. SEM micrographs of the insulation coatings revealed cracks, pinholes and mosaic structure.