Nanoscale characterization of the doped SrZrO3 nanoparticles distribution and its influence on the microstructure of Bi2Sr2CaCu2O8+δ film

Highlights: • A small amount of interfacial SrZrO₃ nanoparticles are epitaxial on the SrTiO₃ substrate. • The intergrowths caused by the SrZrO₃ nanoparticles trigger a high density of lattice distortions and stacking faults. • The maximum shear stress can reach 0.685 GPa due to thermal expansion mismatch. • Intergrowth, lattice distortion, stacking fault, and shear stress are the primary magnetic flux pinning center. -- Abstract: Due to the doping of SrZrO₃ nanoparticles, the performance improvement of Bi₂Sr₂CaCu₂O_8+δ (Bi-2212) high-temperature ceramic superconducting films is significant. To comprehensively explore the reasons for the performance enhancement, in this study, the distribution of doped SrZrO₃ nanoparticles and its influence on the Bi-2212 matrix microstructure were characterized at the nanoscale. A small amount of interfacial SrZrO₃ nanoparticles have a semi-coherent heterointerface with the SrTiO₃ substrate accompanied by a non-ideal arrangement of misfit dislocations. In some cases, the interfacial SrZrO₃ lattice has a tilt of ∼3.5° off the heterointerface. For the SrZrO₃ nanoparticles embedded in the film, due to the different interplanar spacing between the Bi-2212 and the SrZrO₃ lattice, a large number of intergrowths were generated which triggered the subsequent yield of a high density of stacking faults and lattice distortions in the Bi-2212 matrix. Moreover, due to thermal expansion mismatch, the maximum shear stress between the SrZrO₃/Bi-2212 heterointerface reached to 0.685 GPa. The intergrowth, stacking fault, lattice distortion, and shear stress are believed to be primary magnetic flux pinning centers that cause the improved performance of Bi-2212(SrZrO₃) nanocomposite films.