In this work, the effect of BaCeO3 (BCO) and BaZrO3 (BZO) dopants on structural and superconducting properties of YBa2Cu3O7−d (YBCO) superconducting thin films was studied. The main focus was in the flux pinning properties of the doped thin films but also changes in the intrinsic properties were measured. This thesis is based on experimental work but also a molecular dynamics simulation was written to model the angular dependence of critical current, Jc(q ). 

The YBCO films were grown on SrTiO3 single crystal substrates using pulsed laser deposition (PLD). The structural properties of the samples were studied using X-ray diffraction and transmission electron microscopy. Superconducting properties were studied using magnetic and transport measurements. 

As deposited using PLD, BCO creates small particles with concentration-dependent diameter of some nanometres. BZO, in contrast, creates columnar defects parallel to YBCO c axis with concentration-independent diameter being in the range 5–10 nm. Both dopants affect the structure of YBCO although, due to the shape and larger interface area of the BCO particles, BCO creates much larger stress in the YBCO matrix. The enhancements in Jc are most notable in BZO doped samples as the magnetic field is parallel to them. The angular dependence of BCO doped YBCO, on the other hand, is not much affected by the dopant. However, a clear decrease of the anisotropy parameter g is seen. It is triggered by the change of the coherence lengths due to impurity scattering of electrons. 

In contrast to BCO, BZO causes pronounced changes in the angular dependence. As the magnetic field is parallel to the rods, a wide peak in Jc(q ) (c peak) can be seen in an optimal sample. However, if the rods are short or splayed enough, no c peak is seen. The rod morphology can be controlled in many ways, for example the deposition temperature determines whether the columns are splayed or straight and continuous or not. Similar disappearance of the c peak was also seen in multilayer films with BCO and BZO doped layers if the BZO columns were short enough. The disappearance of the c peak was also modelled in a molecular dynamics simulation capable of anisotropic scaling. It can be explained using the vortex path model.