Ceramic Insulation of Bi2Sr2CaCu2O8-x Round Wire for High-Field Magnet Applications

Conductor insulation is a key technology for the development of ultrahigh field superconducting magnets. We have developed a ceramic insulation coating on Bi
₂
Sr
₂
CaCu
₂
O
_8-x
round wire for high field magnet applications. The coating consists of TiO
₂
nanopowder, polymer binders, and other additives. The insulation is uniformly applied on Bi
₂
Sr
₂
CaCu
₂
O
_8-x
wire by dip coating in ceramic slurries. Its thickness is controllable between 10 and 30
$\mu\text{m}$
. The coating is strongly bonded to the wire and reasonably flexible before heat treatment; therefore, the insulated wires can be wound into coils without cracks or spalling. After Bi
₂
Sr
₂
CaCu
₂
O
_8-x
heat treatment, the coating is sintered to provide reliable ceramic insulation. A few pieces of Bi
₂
Sr
₂
CaCu
₂
O
_8-x
wire (including one over 750 m long) are insulated for our Bi
₂
Sr
₂
CaCu
₂
O
_8-x
high-field magnet development program. In this paper, we present the technical details of our insulation process, including the formulation of the coating slurry, and the coating application method. We also addressed issues with respect to improving coating quality.