Control of nanostructure and pinning properties in solution deposited YBa ₂Cu ₃O _7−x nanocomposites with preformed perovskite nanoparticles

Abstract

Solution deposited YBa ₂Cu ₃O _7−x (YBCO) nanocomposites with preformed nanoparticles represent a promising cost-effective approach for superior critical current properties under applied magnetic fields. Nonetheless, the majority of YBCO nanocomposites with high nanoparticle loads (>20%) suffer from nanoparticle coalescence and degraded superconducting properties. Here, we study the influence of nanoparticle concentration (0–25% mol), size (5 nm–10 nm) and composition (BaHfO ₃, BaZrO ₃) on the generation of structural defects in the epitaxial YBCO matrix, key parameter for vortex pinning. We demonstrate that flash-heated superconducting nanocomposites with 20 mol% preformed BaHfO ₃ or BaZrO ₃ perovskite secondary phases feature discrete and small (7 nm) nanoparticles and high density of YBa ₂Cu ₄O ₈ (Y248) intergrowths. We identify a synergy between Y248 intergrowth density and small nanoparticles to increase artificial vortex pinning centers. Also, we validate the multideposition process to successfully increase film thickness of epitaxial nanocomposites with competitive critical currents I _c at 77 K.