Er₂O₃-ZrO₂ insulation coatings on Ag/AgMg sheathed Bi-2212 superconducting tapes by sol-gel process

We have fabricated high temperature insulation coatings on long-length superconducting tapes and wires using a reel-to-reel sol-gel dip coating system for HTS/LTS coils at NHMFL. In this work, 8 mol% Er₂O₃ -ZrO₂ coatings were deposited on Ag or AgMg sheathed Bi₂Sr₂Ca₁Cu₂O_x (Bi-2212) superconducting tapes. The insulation solution was prepared with Zr and Er based organometallic compounds. The gel layers were transformed to amorphous layers at about 300 °C for 30 sec. in air. The ceramic oxide coatings were subsequently formed at 600 °C for 60 sec. in air. The coatings on Ag/AgMg sheathed Bi-2212 tapes were finally densified by annealing at 862 °C for 12 h under oxygen gas flow. These coatings were characterized by means of ESEM, DTA, and XRD. Dielectric constant, breakdown voltage and resistance values of the coatings were measured using a standard multimeter and power supply. ESEM revealed that surface morphology of the coatings is mosaic structure. XRD and DTA studies show that cubic phases formed at between 450 °C and 600 °C. Dielectric constant, high voltage breakdown and resistance values of the insulations were found to be 20, 1096 V at 1.5 mA and 14 M-Ohms, respectively.