Effect of oxygen on the properties of Y-Ba-CuO ceramics

The samples of Y-Ba-CuO ceramics 60×60×60 mm3 in size were synthesized and investigated with provision for their impurity content, crystallography, superconductive and magnetic properties. The conditions of low-temperature thermal treatments, as compared to the sintering ones, are offered that result in degradation of superconductive properties due to partial oxygen removal and their subsequent recovery. The mechanism of copper spin-paramagnetism growth in oxygen-deficient samples is discussed. The intensity of narrow (approximately 3 mrad half-width) component observed in the angular distribution of annihilation photons of partially de-oxygenized samples is found to increase in a constant magnetic field, suggesting the formation of positronium-like states. The intense CuOEH2+ emission line is shown to be present in the spectra of superconductive samples, while it is absent in the non-superconductive state.