Structural and microstructural evolution of Ag-modified Bi-2212 superconducting ceramics with varying sintering temperatures

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Ağıl A. A.

International Journal of Pure and Applied Sciences, cilt.12, sa.1, ss.113-132, 2026 (TRDizin)

Özet

Ag-doped Bi2Sr2CaCu2O8+δ (Bi-2212) superconducting ceramics were synthe-sized by the solid-state reaction method and sintered at 835, 840, and 845 °C to examine the effects of Ag addition and sintering temperature on their structural and microstructural characteristics. X-ray diffraction (XRD) confirmed the dominance of the Bi-2212 phase in all samples. Minor changes in the lattice parameters indicated that Ag did not substitute into the crystal lattice, while a slight increase in the c-parameter at higher temperatures was attributed to oxygen loss. Williamson–Hall analysis revealed that moderate Ag addition (x ≈ 0.03) promoted crystallite growth and reduced lattice strain, resulting in a minimum lattice strain energy density. The unit cell volume and c/a ratio varied systemat-ically with Ag content and sintering temperature. Scanning electron microscopy (SEM) observations showed that Ag addition up to x = 0.03 produced a dense and well-connected microstructure, whereas higher Ag contents (x ≥ 0.05) and higher temperatures led to Ag-rich segregated regions and localized porosity. These findings demonstrate that Ag does not incorporate into the Bi-2212 lattice but acts as a liquid-phase sintering aid that enhances densification and crystal growth at low levels while causing phase segregation and heterogeneity at high concentra-tions. The most uniform structure was achieved in the 3 wt.% Ag-doped sample sintered at 840 °C.