Flux pinning properties in Y₂BaCuO₅-doped YBa₂Cu₃O_y films fabricated with vapor-liquid-solid growth method

High-temperature superconducting REBa₂Cu₃O_y (RE: Rare earth elements, REBCO) films need both a high-speed film fabrication with a well-oriented crystalline texture and an introduction of artificial pinning centers (APCs) to improve critical current densities J_cs in magnetic fields. A vapor-liquid-solid (VLS) growth method enables the REBCO films to grow rapidly with a high quality but makes it difficult to introduce the APCs. In this study, Y₂BaCuO₅ (Y₂11) was doped into YBa₂Cu₃O_y (Y123) films fabricated via the VLS method with a liquid layer of Ba₃Cu₇O₁₀. A microstructure analysis revealed that nano-particle APCs with diameter less than 10 nm were successfully introduced into the YBCO films. The Y₂11-doped Y123 films show the highest critical temperature T_c and the J_c in magnetic fields with a chemical composition ratio close to the stoichiometry of Y123.