Person: Prado Gonjal, Jesús De La Paz
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First Name
Jesús De La Paz
Last Name
Prado Gonjal
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Inorgánica
Area
Química Inorgánica
Identifiers
35 results
Search Results
Now showing 1 - 10 of 35
Item SrCo0.50Fe0.40Ir0.10O3−δ decorated with Pd and La0.8Sr0.2Ga0.83Mg0.17O3−δ: a cleaner electrode for intermediate-temperature solid oxide fuel cells with reduced cobalt content(ACS Applied Energy Materials, 2024) Chivite-Lacaba, Mónica; Prado Gonjal, Jesús De La Paz; Troncoso, Loreto; Cascos Jiménez, Vanessa AmeliaRecent studies related to cathode materials for solid oxide fuel cells (SOFCs) have showcased the feasibility of stabilizing cubic or tetragonal perovskite phases in the SrCoO3−δ system at room temperature. This achievement has been facilitated by partially substituting Co atoms with small amounts of highly charged cations such as Ir4+ in SrCo0.90Ir0.10O3−δ. This specific material exhibits exceptional performance as a cathode for SOFCs operating at intermediate temperatures (800−850 °C). However, it contains a high amount of cobalt, which is both costly and toxic. In this study, our focus has been on further improving this material by reducing its cobalt content, resulting in a cleaner and more cost-effective cathode for SOFCs. The resulting SrCo0.50Fe0.40Ir0.10O3−δ perovskite, synthesized by the citrate method, introduces a 40% composition of Fe in the sites of Co and Ir, effectively decreasing the amount of Co in the material. The crystal structure of this perovskite oxide has been analyzed using X-ray diffraction (XRD) and neutron powder diffraction (NPD), allowing us to establish correlations with its mechanical and electrical properties. In the single-cell test, this material gave reasonable performances as a cathode at intermediate temperatures (800−850 °C), with La0.8Sr0.2Ga0.83Mg0.17O3−δ (LSGM) as the electrolyte. An analysis of the chemical compatibility between the cathode and the electrolyte, LSGM, demonstrated no interaction at elevated temperatures. Thermal expansion coefficient (TEC) measurements exhibited consistent linear expansion across the entire temperature range. Lastly, the perovskite displayed commendable electrical conductivity along with a promising power density measurement of 384 mW/cm2 at 850 °C. These findings collectively suggest the potential of this material as a viable cleaner cathode option for intermediate-temperature SOFCs. Moreover, the cathode was further optimized and the performance of the cell improved, by either infiltrating SrCo0.50Fe0.40Ir0.10O3−δ with a Pd(NO3)2 solution or mixing it with 30% of LSGM electrolyte, resulting in higher power densities (568 and 675 mW/cm2, respectively) in test cells fed with pure H2 as a fuel.Item Lithium‐filled skutterudites by intercalation at ambient‐temperature(Zeitschrift für anorganische und allgemeine Chemie, 2023) Prado Gonjal, Jesús De La Paz; Vaqueiro, Paz; Kowalczyk, Radoslaw; Smith, Ronald; Powell, AnthonyThe incorporation of lithium as a filler species in Co1‐2xFexNixSb3 skutterudites was accomplished by intercalation at 60 °C, using n‐BuLi as a reducing agent. Solid state 7Li NMR and ICP‐MS analysis confirm the presence of lithium in the product phases and provide an estimate of the lithium content. The maximum uptake of lithium increases as cobalt is progressively substituted by an equimolar mixture of iron and nickel. Difference Fourier maps, calculated during Rietveld structure refinement using powder neutron diffraction data, locate the lithium cations at the 2a (0,0,0) sites within the cavities of the skutterudite framework. The intercalation of lithium results in reductions in thermal conductivity of up to 47 %, indicative of phonon glass electron crystal (PGEC) type behaviour. Charge transfer from lithium to the framework that accompanies intercalation results in a substantial decrease in electrical resistivity in lithiated phases and a more metal‐like temperature dependence. The increased carrier concentration also decreases the Seebeck coefficient, with the consequence that modest increases in the figure of merit occur, despite the reduced thermal conductivity.- Project number: PIMCD95/23-24
Item Modelos bidimensionales y tridimensionales para la enseñanza de la Cristalografía y la Mineralogía(2024) Pina Martínez, Carlos Manuel; Ávila Brande, David; Cabeza Llorca, Ana; Cascos Jiménez, Vanessa Amelia; Crespo López, Ángel; Fernández Sequeira, Vinicio; González Illanes, Tamara; López-Acevedo Cornejo, María Victoria; Pallarés Zazo, Ana; Prado Gonjal, Jesús De La Paz; Solana Madruga, Elena; Pimentel Guerra, Carlos; Pina Martínez, Carlos Manuel Item Microwave-assisted synthesis: A fast and efficient route to produce LaMO3 (M=Al, Cr, Mn, Fe, Co) perovskite materials(Materials Research Bulletin, 2011) Prado Gonjal, Jesús De La Paz; Arévalo-López, Ángel Moisés; Morán Miguélez, EmilioA series of lanthanum perovskites, LaMO3 (M=Al, Cr, Mn, Fe, Co), having important technological applications, have been successfully prepared by a very fast, inexpensive, reproducible, environment-friendly method: the microwave irradiation of the corresponding mixtures of nitrates. Worth to note, the microwave source is a domestic microwave oven. In some cases the reaction takes place in a single step, while sometimes further annealings are necessary. For doped materials the method has to be combined with others such as sol–gel. Usually, nanopowders are produced which yield high density pellets after sintering. Rietveld analysis, oxygen stoichiometry, microstructure and magnetic measurements are presented.Item The role of defects in microwave and conventionally synthesized LaCoO3 perovskite(2016) Prado Gonjal, Jesús De La Paz; Gutiérrez-Seijas, Julia; Herrero Ansorregui, Irene; Morán Miguélez, Emilio; Terry, Ian; Schmidt, RainerIn this work we investigate the magnetic, dielectric and charge transport properties of LaCoO3 (LCO) synthesized by two different techniques: microwave assisted and conventionally heated ceramic synthesis. The rapid microwave synthesis conditions are far away from thermodynamic equilibrium and are found to lead to modified crystal defect properties as compared to conventional synthesis. The thermally induced magnetic spin state transition at Ts1 ≈ 80 K is exemplified by temperature (T)-dependent dielectric spectroscopy data, which reveal the appearance of an additional dielectric contribution that is correlated to the transition. Magnetisation, M vs T, and electrical resistivity, ρ vs T, curves show that the additional dielectric phase is strongly influenced by magnetic defects and may be associated with higher spin state clusters in a magnetic spin-state coexistence scenario. We suggest that defects such as oxygen vacancies act as magnetic nucleation centres across the spin state transition Ts1 for the formation of higher spin state clusters in LCO perovskites.Item Microwave-Assisted Synthesis, Microstructure, and Physical Properties of Rare-Earth Chromites(Inorganic chemistry, 2012) Prado Gonjal, Jesús De La Paz; Schmidt, Rainer; Romero, Juan-José; Ávila Brande, David; Amador, Ulises; Morán Miguélez, EmilioThe full rare-earth (RE) chromites series (RE)CrO3 with an orthorhombic distorted (Pnma) perovskite structure and the isostructural compound YCrO3 can be synthesized through a simple microwave-assisted technique, yielding high-quality materials. Magnetization measurements evidence that the Néel temperature for antiferromagnetic Cr3+–Cr3+ ordering strongly depends on the RE3+ ionic radius (IOR), and a rich variety of different magnetic spin interactions exists. Dielectric spectroscopy on sintered pellets indicates electronic inhomogeneity in all samples as manifested by the presence of at least two dielectric relaxation processes associated with grain boundary and grain interior bulk contributions. X-ray diffraction, Raman spectroscopy, and temperature-dependent dielectric permittivity data do not indicate potential noncentrosymmetry in the crystal or concomitant ferroelectricity. Strong correlations between the magnetic and dielectric properties were not encountered, and microwave-synthesized (RE)CrO3 may not be classified as magnetoelectric or multiferroic materials.Item Microwave synthesis & sintering of Sm and Ca co-doped ceria ceramics(International Journal of Hydrogen Energy, 2015) Prado Gonjal, Jesús De La Paz; Heuguet, Romain; Muñoz Gil, Daniel; Rivera Calzada, Alberto Carlos; Marinel, Sylvain; Morán Miguélez, Emilio; Schmidt, RainerIn this work we report on the combined use of microwave (MW) heating sources for the powdersynthesisandthe ceramic sinteringofSmandCaco-doped ceria Ce0.8Sm0.18Ca0.02O1.9 polycrystalline materials for potential application as an electrolyte in intermediatetemperature solid oxide fuel cells (IT-SOFCs). We investigate the crystal structure, ceramic microstructure and the oxygen ion conductivity in detail and compare the latter to conventionally sintered ceramics. MW sintering of ceramic pellets leads to only slightly increased resistivity as compared to conventional sintering, but offers massive energy and time savings for potential industrial production processes. Exceptionally high oxygen ion conductivity without any significant electronic contribution was found in MW synthesized and MW sintered pellets, where the total resistivity, composed of grain boundary and bulk contributions, was found to be in the range of 0.5-1 kohmios at 500 ºC. Sm- and Ca co-doped ceria may be well-suited for electrolyte materials in IT-SOFCs.Item From theory to experiment: BaFe0.125Co0.125Zr0.75O3−δ, a highly promising cathode for intermediate temperature SOFCs(Journal of Materials Chemistry A, 2020) Sánchez Ahijón, Elena; Marín Gamero, Rafael; Molero-Sánchez, Beatriz; Ávila Brande, David; Manjón-Sanz, Alicia; Fernández-Díaz, M. Teresa; Morán Miguélez, Emilio; Schmidt, Rainer; Prado Gonjal, Jesús De La PazIn a recent theoretical study [Jacobs et al., Adv. Energy Mater., 2018, 8, 1702708], BaFe0.125Co0.125Zr0.75O3−δ was predicted to be a stable phase with outstanding performance as an auspicious cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). It is shown here that the theoretical predictions are valid. The material can be synthesized by the citrate method as a single cubic Pm[3 with combining macron]m phase with a significant amount of oxygen vacancies, randomly distributed in the anionic sublattice facilitating oxygen vacancy conduction. A thermal expansion coefficient of 8.1 × 10−6 K−1 suggests acceptable compatibility with common electrolytes. Electrochemical impedance spectroscopy of symmetrical cells gives an area-specific resistance of 0.33 Ω cm2 at 700 °C and 0.13 Ω cm2 at 800 °C. These values are reduced to 0.13 Ω cm2 at 700 °C and 0.05 Ω cm2 at 800 °C when the material is mixed with 30 wt% Ce0.9Gd0.1O2−δ.Item Low thermal conductivity in La-filled cobalt antimonide skutterudites with an inhomogeneous filling factor prepared under high-pressure conditions(Journal of Materials Chemistry A, 2018) Serrano-Sánchez, Federico; Prado Gonjal, Jesús De La Paz; Nemes, Norbert Marcel; Biskup Zaja, Nevenko; Varela Del Arco, María; Dura, Oscar Juan; Martínez, José; Fernández-Díaz, Maria Teresa; Fauth, François; Alonso, José AntonioLa-filled skutterudites LaxCo4Sb12 (x = 0.25 and 0.5) have been synthesized and sintered in one step under high-pressure conditions at 3.5 GPa in a piston-cylinder hydrostatic press. The structural properties of the reaction products were characterized by synchrotron X-ray powder diffraction, clearly showing an uneven filling factor of the skutterudite phases, confirmed by transmission electron microscopy. The non-homogeneous distribution of La filling atoms is adequate to produce a significant decrease in lattice thermal conductivity, mainly due to strain field scattering of high-energy phonons. Furthermore, the lanthanum filler primarily acts as an Einstein-like vibrational mode having a strong impact on the phonon scattering. Extra-low thermal conductivity values of 2.39 W m−1 K−1 and 1.30 W m−1 K−1 are measured for La0.25Co4Sb12 and La0.5Co4Sb12 nominal compositions at 780 K, respectively. Besides this, lanthanum atoms have contributed to increase the charge carrier concentration in the samples. In the case of La0.25Co4Sb12, there is an enhancement of the power factor and an improvement of the thermoelectric properties.Item Optimizing Thermoelectric Properties through Compositional Engineering in Ag-Deficient AgSbTe2 Synthesized by Arc Melting(ACS Applied Electronic Materials, 2024) Prado Gonjal, Jesús De La Paz; García-Calvo, Elena; Gainza, Javier; Durá, Oscar J.; Dejoie, Catherine; Nemes, Norbert Marcel; Martínez, José Luis; Alonso, José Antonio; Serrano-Sánchez, FedericoThermoelectric materials offer a promising avenue for energy management, directly converting heat into electrical energy. Among them, AgSbTe2 has gained significant attention and continues to be a subject of research at further improving its thermoelectric performance and expanding its practical applications. This study focuses on Ag-deficient Ag0.7Sb1.12Te2 and Ag0.7Sb1.12Te1.95Se0.05 materials, examining the impact of compositional engineering within the AgSbTe2 thermoelectric system. These materials have been rapidly synthesized using an arc-melting technique, resulting in the production of dense nanostructured pellets. Detailed analysis through scanning electron microscopy (SEM) reveals the presence of a layered nanostructure, which significantly influences the thermoelectric properties of these materials. Synchrotron X-ray diffraction reveals significant changes in the lattice parameters and atomic displacement parameters (ADPs) that suggest a weakening of bond order in the structure. The thermoelectric characterization highlights the enhanced power factor of Ag-deficient materials that, combined with the low glass-like thermal conductivity, results in a significant improvement in the figure of merit, achieving zT values of 1.25 in Ag0.7Sb1.12Te2 and 1.01 in Ag0.7Sb1.12Te1.95Se0.05 at 750 K.