ABSTRACT
Coated conductors consist of a thin coat of superconductor laid down on a
supporting substrate and buffer layer (Figure 12.1). The coating can be several
micrometers thick. The buffer layer, which is between the substrate and the
superconductor, has highly textured crystallites, and the superconductor takes
this texture when it is deposited on the buffer layer. The texture is "biaxial" as
opposed to the "uniaxial" texture of typical B S C C O superconductors. 1 Thus the
properties of the superconductor are like those of a single crystal, i.e. the crystals are
sufficiently wel I aligned that the grain boundaries offer little resistance to electrical
current. Two methods have been used to produce the oriented buffer layer: the
I B A D a p p r o a c h 2 - 4 which is an ion beam assisted vapor deposition process on
an untextured substrate, and the R A B i T S approach 5 which starts by producing a
textured metallic substrate, obtained by rolling deformation and heat treatment. The
conductor is made in the form of strips with the c axis of the crystals perpendicular
to the plain of the strip. The most common superconducting material which is used
is YiBa?Cu307_,5 ( Y B C O ) . Similar materials with thallium also show promise.