Articles containing a cubic perovskite crystal structure

DETAILED DESCRIPTION What is claimed is: 1.
An article comprised of a monocrystalline substrate capable of supporting the epitaxial deposition of a superconductive R.
sub.
1 A.
sub.
2 C.
sub.
3 orthorhombic perovskite crystal phase and a layer comprised of a cubic perovskite crystal structure satisfying the unit cell formula: R.
sub.
0.
33+z A.
sub.
0.
67 C.
sub.
1-y O.
sub.
3-x wherein A is at least 50 percent barium on an atomic basis with any additional alkaline earths being chosen from the group consisting of strontium and calcium.
C is copper, R is ytterium or a lanthanide other than cerium, praseodymium, promethium and terbium, x is 0.
67 to 1; y is up to 0.
2; and z is up to 0.
1.
2.
An article according to claim 1 wherein R consists essentially of yttrium.
3.
An article according to claim 1 wherein z is up to 0.
08.
4.
An article according to claim 1 wherein A is at least 80 percent barium on an atomic basis.
5.
An article according to claim 4 wherein any additional alkaline earth is strontium.
6.
An article according to claim 1 wherein y is from 0.
05 to 0.
18.
7.
An article according to claim 1 wherein x is from 0.
67 to 0.
85.
8.
An article according to claim 1 in which the cubic perovskite crystal structure satisfies the unit cell formula: Y.
sub.
0.
33+z Ba.
sub.
0.
67 Cu.
sub.
1-y O.
sub.
3-x where x represents 0.
67 to 0.
85; y represents 0.
05 to 0.
18; and z is up to 0.
08.
9.
An article according to claim 1 in which a layer comprised of an R.
sub.
1 A.
sub.
2 C.
sub.
3 orthorhombic perovskite crystal phase overlies said cubic perovskite crystal structure containing layer, where in the R.
sub.
1 A.
sub.
2 C.
sub.
3 phase A is at least 50 percent barium on an atomic basis with any additional alkaline earths being chosen from the group consisting of strontium and calcium, C is copper, and R is ytterium or a lanthanide other than cerium, praseodymium, promethium and terbium.
10.
An article according to claim 9 in which said overlying layer is superconductive.
11.
An article according to claim 1 in which a first layer comprised of an R