Inkjet printing (IJP) is a very appealing cost-effective deposition technique to achieve large-area solution-derived functional films. For many applications, it is very challenging to increase the film thickness in order to achieve competitive performance, for instance, high critical currents in superconducting films. In this paper, the preparation of superconducting YBa2Cu3O7 thick films (∼1.1 μm) using a single deposition is reported. Specific rules for ink design, deposition protocols, and pyrolysis processes are provided.
The most important aspect is to formulate an ink with a solvent having a high boiling point that keeps the whole film wet during deposition to avoid liquid movement due to coffee-ring effects. An additional success has been to modify the ink with a photocurable polyacrylic ester varnish which after polymerization with a UV LED lamp helps keep homogeneous thickness. This varnish also helped avoid the generation of film instabilities (wrinkling or cracking) during pyrolysis. Homogeneous pyrolyzed thick films are transformed into epitaxial thick films with high critical currents. The IJP process is shown to be valid to prepare nanocomposite films using colloidal inks including pre-prepared BaZrO3 nanoparticles. The nanocomposite thick films display enhanced vortex pinning, thus keeping high critical currents under high magnetic fields.
Superconducting materials for emerging technologies
High Performance of Superconducting YBa2Cu3O7 Thick Films Prepared by Single-Deposition Inkjet Printing
Bohores Villarejo, Flavio Pino, Cornelia Pop, Susagna Ricart, Ferran Vallès, Bernat Mundet, Anna Palau, Pere Roura-Grabulosa, Jordi Farjas, Natalia Chamorro, Ramón Yáñez, Xavier Granados, Teresa Puig*, and Xavier Obradors*
The functional properties of cuprates are strongly determined by the doping state and carrier density. We present an oxygen doping study of YBa2Cu3O7-δ (YBCO) thin films from underdoped to overdoped state, correlating the measured charge carrier density, nHnH, the hole doping, p, and the critical current density, Jc. Our results show experimental demonstration of strong increase of Jc with nH, up to Quantum Critical Point (QCP), due to an increase of the superconducting condensation energy.
Combinatorial and high-throughput experimentation (HTE) is achieving more relevance in material design, representing a turning point in the process of accelerated discovery, development, and optimization of materials based on data-driven approaches. The versatility of drop-on-demand inkjet printing (IJP) allows performing combinatorial studies through fabrication of compositionally graded materials with high spatial precision, here by mixing superconducting REBCO precursor solutions with different rare earth (RE) elements.