Process of depositing an alkali metal layer onto the surface of an oxide superconductor

A process for improving the properties of a shaped polycrystalline high temperature copper oxide superconductor, said shaped superconductor having at least one dimension less than about 1 mm, said process comprising;

• (a) depositing an alkali metal onto a clean surface of said shaped superconductor, which clean surface is free from contamination by species other than oxygen, by evaporation from an alkali metal source at a pressure below about 10.sup.-8 torr (1.33.times.10.sup.-6 pa), said shaped superconductor maintained at a temperature of from about 0.degree. C. to about 400.degree. C. during the deposition, to produce an alkali metal layer having a thickness of less than about three monolayers,
• (b) exposing the superconductor with the deposited alkali metal layer to oxygen at a temperature of from about 0.degree. C. to about 400.degree. C., and at an exposure of at least about 10,000 langmuir (1.33.times.10.sup.-4 pa-sec), to thereby produce an improved superconductor.