Аңдатпа
The effect of Co3O4 concentration on the phase composition, surface morphology, geometric density, estimated porosity, compressive strength, and resistive superconducting transition of YBa2Cu3O7−δ ceramics was comparatively investigated. Undoped YBa2Cu3O7−δ and Co3O4-modified YBa2Cu3O7−δ ceramics containing 0.1, 0.5, 1.0, and 1.5 wt.% Co3O4 were prepared from the same nonstoichiometric Y–Ba–Cu–O precursor mixture by a solid-state reaction route followed by oxygen annealing. Phase composition was evaluated by X ray diffraction, surface morphology by scanning electron microscopy, geometric density from specimen mass and dimensions, compressive strength by uniaxial compression, and superconducting transition parameters by four probe electrical resistance measurements. The YBa2Cu3O7−δ phase remained the dominant crystalline phase in all specimens. The sample containing 0.1 wt.% Co3O4 exhibited the highest YBa2Cu3O7−δ content among the modified specimens, 65.2 wt.%, the highest measured compressive strength of 1.95 MPa, and the highest onset transition temperature of 95 K. The highest geometric density of 5.36 g/cm−3 and the lowest estimated porosity of 15.3% were obtained at 0.5 wt.% Co3O4. The specimens containing 1.0 and 1.5 wt.% Co3O4 showed lower YBa2Cu3O7−δ phase fractions and lower geometric density, and did not reach the zero-resistance state within the available measurement range. Although the 0.1 wt.% specimen exhibited a higher onset temperature than undoped YBa2Cu3O7−δ, its lower zero-resistance temperature and broader transition indicate that Co3O4 did not improve all superconducting parameters simultaneously. Since only one specimen was tested for each composition, the density and compressive strength trends should be regarded as preliminary.