Optimization of BaHfO3 Doping Concentration as Secondary Phase in Y0.5Gd0.5Ba2Cu3O7−x Thin Film Prepared by Pulsed Laser Deposition

Abstract

BaHfO3 (BHO)-doped Y0.5Gd0.5Ba2Cu3O7−x (YGBCO) films with a series of doping concentrations (1, 3, 5, and 10 mol%) were fabricated on CeO2 buffer layers by pulsed laser deposition (PLD) technique, and a pristine YGBCO film was also deposited at the same conditions for comparison. X-ray diffraction (XRD) results showed that the undoped and doped YGBCO films had a pure c-axis orientation. While the surface morphology and crystal quality of the BHO-doped YGBCO films deteriorated as the BHO content increased, and the critical current density (J c) at 77 K and self-field ( $J_{\mathrm {c}}^{77,0})$ and critical transition temperature (T c) of the BHO-doped YGBCO films exhibited varying degrees of decline in comparison with the pristine YGBCO film. However, the 5 mol% BHO-doped YGBCO film exhibited greatly enhanced the J c and the highest pinning force densities (F p) at both 4.2 and 65 K, which showed the maximum value of 5776 GN/m3 (4.2 K, H//c) and 117 GN/m3 (65 K, H//c), about 1.5 times that of the undoped YGBCO film. Based on the results, the 5 mol% BHO-doped YGBCO film had the most effective flux pinning centers, which are responsible for strongly improved critical current densities in magnetic fields.