Crystal chemistry and properties of the defect phases YBa/sub 2-x/Cu/sub 3/O/sub y/

The V-A characteristics, with and without an outer magnetic field, the T/sub c/, the phase stability at high temperatures, the oxygen intercalculation capacity in different ambient atmospheres (pO/sub 2/=1 Pa, 4*10/sup 3/ Pa and 2*10/sup 4/ Pa), and the paramagnetic behavior of ceramic samples YBa/sub 2-x/Cu/sub 3/O/sub y/ were correlated with the chemical composition and the applied technology for synthesis of the defect phases. X-ray diffraction, thermogravimetry, electron paramagnetic resonance, and the four-point resistive method were used to study the structure, phase composition, and physical properties of the Ba-deficient YBa/sub 2-x/Cu/sub 3/O/sub y/ phases. Optimal superconducting properties and the lowest contamination of the system were found for the composition YBa/sub 1.95/Cu/sub 3/O/sub y/.