Oxygen isotope effects in yttrium-barium-copper oxides

Superonducting yttrium-barium-copper oxide samples have been highly enriched with O18 (up to 91 96 at. %) by methods that ensure homogeneous distribution of the oxygen isotope throughout all lattice oxygen sites. The preparative routes used include the pyrolysis of nitrates, gas-phase exchange (which does not ensure homogeneous exchange of all sites), oxidation of amorphous YBa2Cu3 alloy, and hydrolysis oxidation of Y-BaF2-Cu thin films. The Tcs of enriched18 samples vary with some methods of preparation. Some enriched17 samples were also prepared for comparison. The composition and structure of materials derived from the various preparative routes were characteized, and their magnetic and electrical properties were measured.