A5074353995- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Electronic and Structural Properties of Oxides
- Magnetic properties of thin films
- ZnO doping and properties
- Multiferroics and related materials
- Superconductivity in MgB2 and Alloys
- Theoretical and Computational Physics
- Superconducting Materials and Applications
- Magnetic Properties and Synthesis of Ferrites
- Chemical and Physical Properties of Materials
- Copper-based nanomaterials and applications
- High-pressure geophysics and materials
- Advanced ceramic materials synthesis
- Copper Interconnects and Reliability
- Ferroelectric and Piezoelectric Materials
- Acoustic Wave Resonator Technologies
- Catalytic Processes in Materials Science
- Transition Metal Oxide Nanomaterials
- Magnetic Properties of Alloys
- Magnetic Properties and Applications
- Semiconductor materials and devices
- HVDC Systems and Fault Protection
- Ga2O3 and related materials
Institut de Ciència de Materials de Barcelona
2013-2022
Consejo Superior de Investigaciones Científicas
2002-2016
Universitat Autònoma de Barcelona
2000-2015
Centre d’Élaboration de Matériaux et d’Études Structurales
1993-2006
Universidad Carlos III de Madrid
2006
Helmholtz Institute Jena
1994-2000
Universitat de Barcelona
1997
Unidades Centrales Científico-Técnicas
1997
Instituto de Ciencia de Materiales de Sevilla
1993
Structural and magnetic properties of γ-Fe2O3 have been studied in isometric nanoparticles ranging from 3 to 14 nm with a narrow particle size distribution. Cation vacancy order is observed for particles larger than 5 diameter giving rise cubic superstructure, while the smallest these vacancies are disordered. All measured showed strong dependence on average crystallite size. For ordered samples, saturation magnetization was found decrease linearly decreasing due surface spin canting effect....
Chemical solution deposition (CSD) has recently emerged as a very competitive technique for obtaining epitaxial films of high quality with controlled nanostructure. In particular, the all-CSD approach is considered to be one most promising approaches cost-effective production second-generation superconducting wires. The trifluoroacetate (TFA) route versatile achieving YBa2Cu3O7 (YBCO) layers critical currents. this work, recent advances towards improvement performance several conductor...
A methodology of general validity to study vortex pinning in YBa2Cu3O7−δ (YBCO) is described. It based on measuring the angular-dependent critical current density a large range temperatures and magnetic fields it permits one identify, separate quantify three basic contributions associated anisotropic–strong, isotropic–strong isotropic–weak centers. The corresponding phase diagrams for these are built up. This applied recently discovered solution-derived YBCO–BaZrO3 nanocomposites which...
The microstructure and critical currents of superconducting YBa2Cu3O7-Y2BaCuO5 composites with small CeO2 additions prepared using a directional solidification procedure have been investigated. cause the decomposition Y2BaCuO5 phase leading to formation Y2O3 BaCeO3. Experimental evidence is given for subsequent nucleation on particles. This new decomposition-nucleation mechanism leads textured YBa2Cu3O7 having enhanced currents. An addition 0.3 wt % can increase Jabc by factor 2 in samples...
In this work we carefully analyze the role of microstructure on magnetic properties Co-doped ZnO nanoparticles prepared by vaporization-condensation method in a solar reactor. We show that close correlation exists between microstructural features and appearance ferromagnetism. Both shape size particles, as well microstructure, can be controlled changing pressure inside evaporation chamber, evidenced transmission electron microscopy micrographs high resolution (HREM). X-ray diffraction...
The achievement of low cost deposition techniques for high critical current YBa2Cu3O7 coated conductors is one the major objectives to achieve a widespread use superconductivity in power applications. Chemical solution are appearing as very promising methodology epitaxial oxide thin films at cost, so an intense effort being carried out develop routes all chemical conductor tapes. In this work recent achievements will be presented towards goal combining different type buffer layers on...
Strain engineering of functional properties in epitaxial thin films strongly correlated oxides exhibiting octahedral-framework structures is hindered by the lack adequate misfit relaxation models. Here we present unreported experimental evidences a four-stage hierarchical development perturbations resulting from progressive imbalance between electronic, elastic and octahedral tilting energies La0.7Sr0.3MnO3 grown on SrTiO3 substrates. Electronic softening Mn - O bonds near substrate leads to...
We report a detailed study of the magnetic and magnetotransport properties Sr2FeMoO6 ceramics having controlled concentration antisite (AS) defects. It is found that high-field differential susceptibility exists in all samples, which increases with AS. Similarly, magnetoresistivity develops mimics susceptibility. These observations suggest defects promote some frustration. High-resolution electron microscopy studies have allowed observation existence antiphase boundary structure.
The influence of three processing parameters, temperature, gas flow rate and water pressure, on the YBa2Cu3O7 film growth LaAlO3 single-crystal substrates from trifluoroacetate precursors has been investigated optimal conditions to achieve high critical currents have determined. We found that maximizing current density are those where nucleation a-axis oriented grains is minimized, as determined by μ-Raman spectroscopy. Under these normal state resistivity very near single crystals because a...
A study of the structural and magnetic characteristics strongly frustrated kagome system ${\mathrm{SrGa}}_{12\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Cr}}_{\mathit{x}}$${\mathrm{O}}_{19}$ (1\ifmmode\times\else\texttimes\fi{}9) is reported with focus on effects ion dilution. High-resolution powder neutron diffraction shows no evidence long-range ordering down to 1.5 K a nearly random substitution Cr by Ga atoms within octahedral sites. An intrinsic quasibidimensional structure integrated...
The complex microstructure of directionally solidified ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}}$${\mathrm{Y}}_{2}$${\mathrm{BaCuO}}_{5}$ composites having up to 30 vol % 2:1:1 precipitates with sizes down 0.1 \ensuremath{\mu}m and critical currents above ${10}^{5}$ A/${\mathrm{cm}}^{2}$ at 77 K zero magnetic field has been investigated through detailed transmission electron microscopy observations. It is shown that samples a high...
We present a study of flux pinning by in-plane partial dislocations in melt-textured grown ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}/{\mathrm{Y}}_{2}{\mathrm{BaCuO}}_{5}$ (123/211). The are generated high oxygen pressure (HOP) postprocessing treatment as confirmed transmission electron microscopy (TEM). In order to characterize the dislocation density and perimeter surface ratio (PSR) associated stacking faults large number TEM micrographs have been analyzed. demonstrate that...
The mechanisms controlling stress relief during the drying and pyrolysis processes of trifluoroacetate metal-organic precursors have been elucidated in view high rate fabrication epitaxial superconducting YBa2Cu3O7 thin films. Combining FTIR, TGA, film thickness evolution measurements, we conclude that gel sintering occurs below T ∼ 250 °C while densification, due to pyrolysis, range 250−310 °C. Stress is driving force leading smooth or structurally inhomogeneous films, displaying buckling...
The evolution from a partially oriented granular microstructure to dense epitaxial one in CeO2 films deposited chemical solutions on Y2O3-stabilized cubic ZrO2 (YSZ) has been investigated using cross-section transmission electron microscopy (XTEM), energy-loss spectroscopy (EELS), X-ray photoelectron (XPS), atomic force (AFM), diffraction (XRD), and reflectometry (XRR). In crystallization solutions, undercoolings are typically high enough promote homogeneous heterogeneous nucleation with...
We describe the conversion of yttrium, barium, and copper trifluoracetate-derived solid precursors to epitaxial YBa2Cu3Ox superconducting ceramics on (001)-oriented LaAlO3 substrates. Transmission electron microscopy, energy loss spectroscopy, energy-dispersive X-ray analysis, diffraction are used characterize reaction path nucleation mechanism yielding high critical current YBa2Cu3O7. Our results show that pyrolysis trifluoracetate solutions yields a nanostructured, partially amorphous...
Self-organized rows of CeO2 nanodots (see image) have been achieved through centering islands within the terraces vicinal perovskite substrates. The extraordinary effectiveness for lateral confinement, with islands' heights ∼ 20 times larger than lattice steps, results from non-coherent vertical interfaces at substrate steps between dissimilar crystallographic structures.
Directionally solidified composites display a complex microstructure with several defects coexisting in the matrix and hence identification of flux-pinning mechanisms requires detailed analysis critical currents. In this work we review formation mechanism twins, stacking faults, microcracks, subgrain boundaries dislocations connection refining strategies (211 phase) inclusions modifications generated through prolonged oxygen annealings high-temperature plastic deformation ceramic. The...
Chemical solution growth of epitaxial YBa2Cu3O7 thin films on single crystalline substrates has been investigated using trifluoroacetate precursors. The concentration the starting was selected to achieve a final film thickness 250 nm. First, it is shown that high quality can only be achieved if an homogeneous nanocrystalline obtained after spin coating deposition and pyrolysis steps. Secondary phases such as BaCuO2, Y2BaCuO5 CuO remain temperature process, when macrosegregation detected...