Improvement in structure and superconductivity of YBa2Cu3O6+ δ ceramics superconductors by optimizing sintering processing

Polycrystalline YBa2Cu3O6+δ bulks were synthesized by sol-gel method. Sintering processing played a vital role in the evolution of phase structure and microstructure, and thus significantly influenced their superconducting properties. The influence of calcination temperature, sintering temperature, on the bulks structure, morphology and superconducting behaviors were investigated. The results showed that the oxygen content drastically increased with calcination temperature and sintering temperature. The SEM images revealed that the grains grew up monotonously with increase of calcination temperature. With increased calcination and sintering temperature, the resistivity was reduced gradually and the superconducting properties increased. Moreover, it was found that the optimal superconducting properties (with the highest superconducting transition temperature T c onset and the narrowest transition width ΔT) were obtained at calcination temperature of 900 °C and sintering temperature of 950 °C.