The potentiality of preformed nanoparticles to control vortex pinning and dynamics of chemical solution nanocomposites is disentangled by correlating preparation, microstructure and properties
High temperature superconducting nanocomposites are a new class of materials that arose in the last decade based on the potentiality of introducing artificial pinning centers of nanometric size in REBa2Cu3O7-x (REBCO, RE=rare earth). The capability of introducing non-superconducting nanometric secondary phases was realized by different growth techniques (pulsed laser deposition, metalorganic chemical vapor deposition, chemical solution deposition). Initially, all were based on the spontaneous segregation of secondary phases during the epitaxial growth of REBCO. Recently, we pioneered the fabrication of solution-derived nanocomposites using preformed nanoparticles prepared by solvothermal methods through their stabilization in REBCO precursor solutions.
Here we demonstrate , for the first time, that non-reactive BaZrO3 and BaHfO3 perovskite preformed nanoparticles are suitable for growing high quality epitaxial films, and coated conductors with a homogeneous distribution and controlled particle size. This study could be extended to thick nanocomposite films, up to 0.8 μm, with a single deposition using ink jet printing. Nanocomposites up to 20 %–25 % mol without any degradation of the superconducting properties are achieved. However, the vortex pinning effects induced by these nanoparticles requires of an extensive study of the electrical transport properties as function of temperature, magnetic field and orientation of the magnetic field.
We need to distinguish between the different defects and contributions that interfere in the results correlating with corresponding microstructure. A quantitative analysis of vortex pinning strength and energies , associated with different kinds of natural and artificial pinning defects, enables us to unravel the different pining regions of the H–T phase diagram, which provides a unique tool to design the best vortex pinning landscape under different operating conditions.
This study is then extended to the vortex dynamics regime, studying the angular dependence of the flux creep properties of nanocomposites, for the first time, from electrical transport measurements .
Ziliang Li,1 Natalia Chamorro,2 Ferran Vallès1, Cornelia Pop,1 Bernat Mundet,1 Victor Rouco,1 Mariona Coll,1 Jaume Gazquez,1 Roger Guzman,1 Joffre Gutierrez,1 Bohores Villarejo,1 Flavio Pino,1 Josep Ros,2 Susagna Ricart,1 Anna Palau,1 Xavier Obradors,1 Teresa Puig1
1 Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
2 Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, Spain
 Epitaxial YBa2Cu3O7-x nanocomposite films and coated conductors from BaMO3 (M = Zr, Hf) colloidal solutions.
Supercond. Sci. Technol. 31, 044001 (2018)
 Disentangling vortex pinning landscape in chemical solution deposited superconducting YBa2Cu3O7-x x films and nanocomposites.
Supercond. Sci. Technol. 31, 034004 (2018)
 Angular flux creep contributions in YBa2Cu3O7-delta nanocomposites from electrical transport measurements.
Scientific Reports 8, 5924 (2018)
Schematic representation of the different defects that may contribute to pin vortices in HTS nanocomposites (a), scanning transmission electron microscopy image of a YBCO nanocomposite with the addition of 20%mol of preformed BaZrO3 nanoparticles, where the interaction with stacking faults is observed (b).