Enhanced flux pinning in GdBaCuO bulk superconductors by Zr dopants

We, respectively, fabricated GdBa2Cu3O7−δ (Gd123) single domain superconductors by melt growth process in air with Gd2Ba4CuZrOx (GdZr2411) and nanosize ZrO2 dopants. The microstructures and superconducting properties were investigated by scanning/transmission electron microscopy (SEM/TEM) and SQUID. GdZr2411 and BaZrO3 particles with the average size of 50 nm were observed in the GdZr2411 and nanosize ZrO2 doped Gd123 bulks by TEM, respectively. Critical current density (Jc) was enhanced up to 100,000 A/cm2 at 77 K and self-field with 0.4 mol% nano-sized ZrO2. The present study also showed that small amount GdZr2411 dopants (8 mol%, ratio to Gd123) were effective to induce a δTc-type pinning.