Nucleation and growth rate influence on microstructure and critical currents of TFA-YBa2Cu3O7 under low-pressure conditions

ACS Appl. Electron. Mater.

Hauck

Barthlott

et al. 2021

Electrical conductivity relaxation was measured to investigate the kinetics of oxygen incorporation (in-diffusion process) and excorporation (out-diffusion process) in different epitaxial REBa2Cu3O7−δ thin films prepared by chemical solution deposition. The oxygen diffusion in these compounds happens in two distinct regimes with different activation energies, which depend on the compound. As the detailed X-ray analysis of similarly processed REBa2Cu3O7−δ films revealed, the transition temperature between these two regimes is compatible with a transition in the oxygen ordering in the Cu–O chains from the Ortho-II phase to the Ortho-I phase. These transitions may be of great importance for further optimization of the oxygenation process during the synthesis of these compounds but may depend not only on the rare-earth (RE) element but also on further factors such as variations of stoichiometry. The presented electrical conductivity measurements provide easy access to the determination of these transition temperatures.

Section: Methodsmentioning

confidence: 99%

Determination of the Oxygen Chain Ordering in REBa₂Cu₃O_7–δ by Electrical Conductivity Relaxation Measurements

ACS Appl. Electron. Mater.

Hauck

Barthlott

et al. 2021

“…The films conductance was determined by electrical measurements carried out using a standard system reported elsewhere. 18,19,95,96 It consists of a 4-probe contact in a Van der Pauw configuration. The sample is held in the center of a 22 mm furnace tube that allows controlling the temperature and gas atmosphere.…”

Section: Methodsmentioning

confidence: 99%

Untangling surface oxygen exchange effects in YBa₂Cu₃O_6+xthin films by electrical conductivity relaxation

Phys. Chem. Chem. Phys.

Sánchez-Valdés

Stangl

et al. 2017

Self Cite

The kinetics of oxygen incorporation (in-diffusion process) and excorporation (out-diffusion process), in YBaCuO (YBCO) epitaxial thin films prepared using the chemical solution deposition (CSD) methodology by the trifluoroacetate route, was investigated by electrical conductivity relaxation measurements. We show that the oxygenation kinetics of YBCO films is limited by the surface exchange process of oxygen molecules prior to bulk diffusion into the films. The analysis of the temperature and oxygen partial pressure influence on the oxygenation kinetics has drawn a consistent picture of the oxygen surface exchange process enabling us to define the most likely rate determining step. We have also established a strategy to accelerate the oxygenation kinetics at low temperatures based on the catalytic influence of Ag coatings thus allowing us to decrease the oxygenation temperature in the YBCO thin films.

“…Of course, an equivalent approach to trap small nanoparticles is, as suggested by eq. (1), to increase the YBCO film growth rate R* through processing parameters such as P H2O or P T [63,64]. From the microstructural analysis of these films, Figures 7b and 7c, we observe the formation of highly epitaxial YBCO films, although reactivity was not avoided, resulting in BaCeO 3 NPs around 20 nm in size.…”

Section: Growth and Characterization Of Nanocompositesmentioning

confidence: 96%

Epitaxial YBa₂Cu₃O_7−xnanocomposite thin films from colloidal solutions

Supercond. Sci. Technol.

Keukeleere

Garzón

et al. 2015

111

A methodology of general validity to prepare epitaxial nanocomposite films is reported based on the use of colloidal solutions containing different crystalline preformed oxide nanoparticles (ex-situ nanocomposites). The trifluoroacetate (TFA) metal-organic chemical solution deposition route is used with alcoholic solvents to grow epitaxial YBa 2 Cu 3 O 7 (YBCO) films. For that reason stabilizing oxide nanoparticles in polar solvents is a challenging goal. We have used scalable nanoparticle synthetic methodologies such as thermal and microwave-assisted solvothermal techniques to prepare CeO 2 and ZrO 2 nanoparticles. We show that stable and homogeneous colloidal solutions with these nanoparticles can be reached using benzyl alcohol, triethyleneglycol, nonanoic acid, trifluoroacetic acid or decanoic acid as protecting ligands, thereby allowing subsequent mixing with alcoholic TFA solutions. An elaborate YBCO film growth analysis on these nanocomposites allows the identification of the different relevant growth phenomena, e.g. nanoparticle pushing towards the film surface, nanoparticle reactivity, coarsening and nanoparticle accumulation at the substrate interface. Upon mitigation of these effects, YBCO nanocomposite films with high self-field critical currents (J c 3-4 MA/cm 2 at 77 K) were reached, indicating no current limitation effects associated to epitaxy perturbation, while smoothed magnetic field dependences of the critical currents at high magnetic fields and decreased effective anisotropic pinning behavior confirms the effectiveness of the novel developed approach to enhance vortex pinning. In conclusion, a novel low cost solution-derived route to high current nanocomposite superconducting films and coated conductors has been developed with very promising features.