The Influence of Substrate Temperature of Seed Layer on the Structure and Superconducting Property of BaHfO3-Doped Y0.5Gd0.5Ba2Cu3O7−δ Film Prepared by Pulsed Laser Deposition

For various practical applications, excellent superconducting properties under magnetic field of REBa2Cu3O7−δ (RE = rare earth elements (REBCO))-coated conductors are required, which can be fabricated by introducing artificial pinning centers, such as second-phase dopant. It is well known that BaMO3 (M = Zr, Sn, or Hf) can form self-organized nanorods in REBCO matrix and improve the critical current density (Jc) under applied magnetic field. However, with increasing dopant level, the critical temperature Tc and Jc at 77 K in self-field decreased. In order to inhibit the degradation of the Jc in self-field, we fabricated 5 mol% BaHfO3 (BHO)-doped Y0.5Gd0.5Ba2Cu3O7−δ (YGBCO) seed layers on CeO2-buffered IBAD-MgO tapes by pulse laser deposition (PLD) at a laser repetition of 10 Hz and different substrate temperature Tseed, and subsequently deposited 5-mol% BHO-doped YGBCO upper layers at 160 Hz and higher substrate temperature. The effect of Tseed on the quality of the 5-mol% BHO-doped YGBCO upper layer was investigated. With increasing Tseed from 710 to 820 ∘C, the Δφ value of YGBCO (103) reflection first decreased and then increased, while the Jc at 77 K increased with increasing Tseed to 790 ∘C and decreased at higher Tseed. The 5-mol% BHO-doped YGBCO layer with a seed layer deposited at 790 ∘C had the highest Jc (77 K, self-field) of 4.0 MA/cm2.