Composite with Y-BA-CU-O superconductive film

A composite is produced comprised of Y--Ba--Cu--O superconductive film having a zero resistance transition temperature of at least about 38 K, a zirconium dioxide film and a substrate wherein the zirconium dioxide film is intermediate the superconductive film and the substrate.

EXAMPLE 1 
The substrate was oxidized silicon. 
ZrO.sub.2, Y, Ba, and Cu were used as evaporation sources. 
The chamber was evacuated to produce an evacuated chamber with a residual 
pressure no greater than about 10.sup.-5 torr and such residual pressure 
was maintained throughout all of the vapor depositions. 
The zirconium dioxide was evaporated onto the substrate to produce a film 
with a thickness of about 0.4 microns. The film covered the entire face of 
the substrate and from other work it was known that it was microscopically 
pore-free. 
Sequential layers of Cu, Ba and Y of 21.4, 77 and 20 nanometers thickness, 
respectively, were evaporated on the zirconium dioxide film and this 
sequence of metals was repeated six times to form an 18-layer stack with a 
total thickness of 0.6 micron. The 18-layer stack of another specimen 
prepared simultaneously in the same manner was determined to have the 
overall composition of YBa.sub.1.9 Cu.sub.3.5. 
The resulting structure was annealed immediately after deposition in an 
oxygen ambient at atmospheric pressure at 800.degree. C. for five minutes 
and cooled at 2.degree. C. per minute. 
The superconductive film had a zero resistance transition temperature of 38 
K. The presence of the orthorhombic structure was inferred from resistance 
measurements. The superconductive film was comprised of a single layer 
which was continuous, appeared to be pore-free, and had a thickness of 
about 0.6 microns. 
Further annealing for five minutes at 850.degree. C. and cooling at the 
same rate increased the transition temperature to 47 K. 
EXAMPLE 2 
This example was carried out in substantially the same manner as Example 1 
except as noted herein. 
Barium fluoride was used instead of barium as the evaporation source. A 
controlled leak of oxygen was introduced into the chamber, which raised 
the residual pressure to about 10.sup.-5 torr. 
Before annealing, the 18-layer stack of another specimen prepared 
simultaneously in the same manner was determined to have the overall 
composition of YBa.sub.1.8 Cu.sub.3.0. 
The annealing atmosphere was at about atmospheric pressure. It was 
comprised of oxygen until the annealing temperature of 850.degree. C. was 
reached. Wet oxygen was then introduced, i.e. oxygen which had been 
saturated with water at room temperature, and the specimen was annealed in 
the wet atmosphere at 850.degree. C. for 3.5 hours. It was then cooled 
only in oxygen at a rate of about 5.degree. C. per minute to about 
550.degree. C. where it was held for about 30 minutes and then cooled to 
room temperature at about 2.degree. C. per minute. 
The superconductive film had a zero resistance transition temperature of 83 
K. The presence of the orthorhombic crystal structure was inferred from 
resistance measurements. The superconductive film was comprised of a 
single layer which was continuous, appeared to be essentially pore-free, 
and had a thickness of about 0.5 microns. 
An elemental depth profile by x-ray photoelectron spectroscopy of another 
specimen prepared simultaneously in the same manner showed no 
interdiffusion between the superconductive film and the substrate, and the 
superconductive film contained about 4 atomic % fluorine throughout the 
film thickness.