Er/sub 2/O/sub 3/-ZrO/sub 2/ 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% Er/sub 2/O/sub 3/-ZrO/sub 2/ coatings were deposited on Ag or AgMg sheathed Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 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/spl deg/C for 30 sec. in air. The ceramic oxide coatings were subsequently formed at 600/spl deg/C for 60 sec. in air. The coatings on Ag/AgMg sheathed Bi-2212 tapes were finally densified by annealing at 862/spl deg/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/spl deg/C and 600/spl deg/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.