Optimal BZO Doping in YBCO Films Grown on Single Crystal STO and Buffered NiW Substrates

The influence of the BaZrO₃ (BZO) dopant concentration on structural and superconducting properties of YBa₂Cu₃O₆₊x (YBCO) thin films deposited on single crystal SrTiO₃ (STO) and buffered NiW metal substrates is investigated. Depending on the applied temperature and external magnetic field, the optimal BZO content n_opt is found to vary so that irrespective of substrate used, in higher magnetic fields also higher n_opt is needed. Moreover, the n_opt of 4wt.% in YBCO films grown on STO is increased up to 7.5wt.% in films on NiW, especially in fields above 1 T. This phenomenon is qualitatively explained by the difference in size, shape and the distribution of BZO pinning centers and other structural disorders in the YBCO matrix. The results substantially affect to the development of the optimal flux pinning structure in future applications of high-temperature superconductors.