Mechanism of Solid Solution-Driven Texture Induced by Ag Doping in YBCO Superconductor

Since the discovery of YBa₂Cu₃O_7-δ (YBCO or Y123), enhancing its superconducting and mechanical properties has been a major focus. Ag doping is a promising strategy for bulk materials, but its mechanism remains debated, particularly regarding whether Ag segregates at grain boundaries or enters the lattice. The origin of the enhancement remains unclear, as conventional powder-doping methods hinder gradient formation and obscure key effects at specific doping levels. Here, we propose a dual-material co-extrusion and freeze-drying strategy to construct a macroscopic Ag-YBCO interface, where directional pores in YBCO enable Ag diffusion and compositional gradient formation at high temperatures. Experiments reveal a [001]-oriented YBa₂Cu_3-xAg_xO_7-δ solid solution with coherent interfaces with Y123, which transmit crystallographic orientation at the atomic scale and promote orientated Y123 growth. First-principles calculations reveal that Ag substitution-induced lattice relaxation plays a key role in driving texture formation. As a result, the composite exhibits a significantly enhanced critical current density (J_c) while maintaining a stable critical temperature (T_c), accompanied by a transition in the fracture behavior from intergranular to transgranular fracture. This work reveals the mechanism of solid solution-driven texture induced by Ag doping in YBCO, providing new insights into dopant-mediated texture evolution in REBCO (Re = rare earth) superconductors.