DIRECTED REACTION PROCESS PRODUCING SINGLE-PHASE SUPERCONDUCTING COMPOUND YBA2CU3O6.5+DELTA

A directed reaction process (DRP) based on physico-chemical principles has been used for producing single-phase 90 K 'zero-resistance' superconducting compound YBa//2Cu//3O//6//. //5// plus // delta . The reliability of the DRP has been well proved by the stability and reproducibility of results in resistance and a. c. magnetic susceptibility measurements of samples taken randomly from five consecutive batches of products. The products were identified by X-ray diffraction as single-phase polycrystalline material of orthorhombic structure with lattice parameters a equals 3. 89A, b equals 3. 82A and c equals 11. 65A. The nonstoichiometric fraction, value, was determined to be plus 0. 27.