Synthesis of Y-123 superconductor without oxygen annealing

This paper reports the synthesis of YBa2Cu3O7-δ superconductors without external oxygen annealing. Polycrystalline samples are synthesized with nominal compositions. YBa2Cu3HgxOy (0 ≤ x ≤ 0.3). The synthesis was carried out in an open atmosphere by two-stage, solid-state reaction method. Initially, the stoichiometric composition of Y2O3, BaCO3 and CuO was calcined twice at 925 degC for 24 hours and then the pellets of HgO added Y-123 compound were sintered at 650 degC for 24 hours. The x-ray diffraction patterns of the samples revealed monophasic Y-123 nature without any trace of Hg or related materials. The superconducting behaviour was studied by low temperature R-T measurement. The HgO added samples showed metallic behaviour followed by the superconducting transition. Some of the HgO added samples exhibited onset superconductivity around 100 K. The scanning electron micrograph of these samples showed non-uniform grain size with substantial grain inter-diffusion. (author)