The effect of Ca substitution in Ba site of Y(Ba1âxCax)2Cu3O7âδ, (x = 0.00, 0.04, 0.08, 0.1 and 0.125), ceramics prepared by thermal treatment method was investigated. Surface morphology, structural and superconducting were studied using field emission electron microscope (FESEM), X-ray Diffraction (XRD) and four-probe method. FESEM analysis showed an increasing of samplesâ grain size, homogeneity and compactness with increasing of Ca substitution. From XRD, the samples had orthorhombic crystal structure of space group Pmmm besides small amount of unknown peaks. The critical temperature (Tc R=zero) decreased from 87 K for the pure sample to 80 K for sample with x = 0.08, and it remained the same for samples with x ⩾ 0.08. Sample with x = 0.04 showed the sharpest superconducting transition (ÎTc), which could be due to good microstructure morphology and better crystallinity. Keywords: YBa2Cu3O7âδ, Ca substitution, Thermal treatment, X-ray Diffraction, Orthorhombic, Critical temperatur

YBa₂Cu₃O_7−δ (Y-123) bulk superconductors with the addition of (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 wt.%) SnO₂ nanoparticles were synthesised via a thermal treatment method. The influence of SnO₂ addition on the superconducting properties by means of critical temperature, T_c, AC susceptibility, phase formation and microstructures, including its elemental composition analysis, were studied. Sharp superconducting transition, ∆T_c, and diamagnetic transition were obtained for all SnO₂-added samples. It was observed that sample x = 0.4 with a Y-123 phase percentage of 95.8% gives the highest T_c, smallest ∆T_c, and the sharpest diamagnetic transition in the normalised susceptibility curves. The microstructure also showed an excess of Sn precipitates on the sample’s surface at x = 0.8 and above. As such, the best superconducting properties were observed at x = 0.4 SnO₂ addition inside the Y-123 host sample.