Characteristics of high-performance BaHfO₃-doped SmBa₂Cu₃O_y superconducting films fabricated with a seed layer and low-temperature growth

BaHfO₃(BHO)-doped SmBa₂Cu₃O_y (SmBCO) superconducting films were fabricated with a seed layer and low-temperature growth (LTG technique) via pulsed laser deposition. The LTG technique enables the fabrication of high-quality SmBCO films even at a low substrate temperature during the deposition, and also greatly increases the number density of BHO nano-rods. Transmission electron microscopy observations showed that the 5.6 vol% BHO-doped sample had a high number density [(4.8 ± 0.3) × 10³ μm^-2] of small (5.4 ± 0.7 nm) BHO nano-rods. This sample exhibits maximum flux pinning forces (F_p) of 405 GN m^-3 in 9.0 T at 40 K and 105 GN m^-3 in 9.0 T at 65 K. The high density and small size of the nano-rods in a REBa₂Cu₃O_y matrix (where RE is a rare earth element) is considered to be very effective for enhancing F_p at low temperatures under a high field.