Impact of calcination temperature on the microstructure and superconductivity of YBa2Cu3O7−δ ceramic prepared via modified thermal decomposition method

This study explores the impact of calcination temperature on the characteristics of YBa₂Cu₃O_7−δ (Y-123) ceramic superconductors, synthesized using a novel modified thermal decomposition (MTD) method. It aims to optimize the relationship between calcination conditions and superconductor performance, which is critical for advancing the utility of high-temperature superconductors (HTS). The calcination process involved two distinct temperatures: 850 °C (Group A) and 910 °C (Group B), each sustained for a duration of 24 h. Following calcination, the samples underwent sintering at varying temperatures: 920 °C, 950 °C, and 980 °C. This process facilitates the examination of how thermal treatment affects the structure-property relationship to find the best conditions for enhanced superconductor performance. The characterization techniques employed encompassed thermogravimetric analysis (TGA/DTG), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and four-point probe measurements (4PP). Thermal stability was examined using TGA-DTA analysis. The XRD analysis revealed the existence of the orthorhombic structure featuring the Y-123 phase in both Group A and Group B with a minor secondary phase, Y₂BaCuO₅ (Y211). The samples calcined at 910 °C exhibited the highest critical temperatures, such as T_c−onset (93.72 K) and T_c−zero (90.27 K), with the lowest superconducting transition width, ΔT_c (3.45 K), at a sintering temperature of 980 °C. Furthermore, an increase in both homogeneity and density was noted with the gradual rise in sintering temperature. FESEM analysis revealed that the sample in Group B exhibited the most densely compacted grain structure and the highest T_c−zero, implying that enhanced interconnectivity among the grains leads to an elevation in T_c−zero. This study underscores the significance of precise thermal processing and introduces a viable method for synthesizing high-T_c superconductors.