Melt growth and microstructure development of high critical current REBa2Cu3O7 superconductors with a natural mixture of rare earths

Abstract

A natural mixture of heavy rare earth oxides has been used to prepare high critical current bulk superconducting ceramics which may be used in electrotechnical devices. Melt processing of a starting mixture of REBa2Cu3O7 and Y2BaCuO5 powders (RE denotes natural mixture of rare earth elements), leads to a final ceramic composite REBa2Cu3O7/RE2′BaCuO5, where RE and RE′ are different mixtures of heavy rare earths and yttrium. It is found that the superconducting matrix and the core of the large RE2′BaCuO5 particles are yttrium rich while the small RE2′BaCuO5 particles are rich in heavy RE ions. The differential solubility of the rare earths in the high-temperature semisolid state leads to a strong inversion of the rare earth composition between the superconducting matrix and the insulating precipitates which is originated during the melt growth process. The superconducting properties of the new compound having natural RE mixtures are found to be very similar to those of pure YBa2Cu3O7/Y2BaCuO5 melt textured composites.