Abstract This study investigates the structural, electrical, and magnetic properties of YBa 2 Cu 3− x Zn x O 7− δ (Y-123) and Y 3 Ba 5 Cu 8− x Zn x O 18− δ (Y-358) superconductors synthesized via the sol–gel method, where copper sites were partially substituted with zinc ( x = 0.00–0.15). Dense polycrystalline samples were obtained following calcination, sintering, and final heat treatment at 930 °C. Structural and microstructural changes with Zn doping were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), while electrical-superconducting and magnetic properties were determined by resistivity ( ρ – T ) and vibrating sample magnetometry (VSM) measurements. X-ray diffraction and SEM analyses show that Zn doping up to x = 0.05 preserves phase purity and structural stability in both Y-123 and Y-358, whereas higher Zn contents ( x ≥ 0.10) induce crystallographic disorder, secondary phases, reduced grain size, and increased porosity, particularly in the Y-358 superconducting phase. Electrical measurements reveal a systematic suppression of critical transition temperature, broadening of the transition, and reduced mobile hole concentration with Zn/Cu substitution, driving both systems into the underdoped regime due to reduced hole concentration, enhanced carrier scattering, and disorder in the Cu-O 2 planes. In other words, excess Zn disrupts the stabilization of superconducting clusters, weakens electronic bridging, and alters the density of states near the Fermi level, degrading superconductivity through both structural and electronic localization effects. Magnetic characterizations confirm a strong reduction in critical current density ( J c ) and flux pinning force ( F p ) with Zn doping, linked to pair-breaking and vortex mobility arising from nonmagnetic Zn 2+ ions in the active CuO 2 planes. Compared with Y-358, the Y-123 phase exhibits greater tolerance to Zn-induced disorder and more stable pinning characteristics. These findings provide comparative information about the role of Zn doping in modulating charge carrier dynamics, flux pinning, and superconducting stability of Y-123 and Y-358 phases, underscoring the importance of compositional control for high-T c superconductor optimization.
Guducu et al. (Mon,) studied this question.