Critical Current Density of YBa_2Cu_3O_(7-x) Films with BaZrO_3 Inclusions On SrTiO_3 and Al_2O_3 Substrates

摘要

Recently, many efforts have been dedicated to the development of a reliable technology for the introduction of artificial pinning sites in YBa_2Cu_3O_(7-x) (YBCO) films with the aim of improving the in-field J_c performances. One of the most effective technique resulted to be the inclusion of BaZrO_3 (BZO) second phase embedded in the YBCO films. In this contribution we present J_c measurements on BZO-added YBCO films deposited on SrTiO_3 (STO) and CeO_2-buffered-Al_2O_3 (ALO) substrates. Samples were deposited by pulsed laser ablation technique using a composite YBCO + 5mol.% BZO target at the optimum conditions for fully oxygenated c-axis oriented YBCO films. Despite of a slight T_c reduction, BZO addition in YBCO-STO films resulted in an improvement of in-field performances with the appearance of a J_c plateau in the low field region which extends up to about 2.5 Tesla irrespective of the temperature at least in the investigated range (down to 65K). On the other hand, samples deposited on ALO did not exhibit any remarkable difference neither in the J_c value nor in the magnetic field dependences as compared with pure YBCO. The presence of 0°(magnetic field parallel to the c-axis) peaks in the J_c. angular behaviour revealed a c-axis correlated character of the pinning forces in BZO added YBCO films grown on both STO and ALO substrates. X-ray diffraction measurements and AFM investigations were carried out in order to determine the influence of BZO addition on films crystalline quality and microstructure.