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
6 results
Search Results
Now showing 1 - 6 of 6
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 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 Structural and physical properties of microwave synthesized orthorhombic perovskite erbium chromite ErCrO3(Journal of the European Ceramic Society, 2012) Prado Gonjal, Jesús De La Paz; Schmidt, Rainer; Ávila Brande, David; Amador, Ulises; Morán Miguélez, EmilioRare-earth chromite ErCrO3 powder was synthesized from metal nitrate precursors using microwave synthesis. (Micro-) structural characterizations were performed using X-ray diffraction, Rietveld refinement, High Resolution Transmission Electron Microscopy and Electron Micro-Diffraction. Magnetization vs. temperature measurements revealed anti-ferromagnetism with TNeel ≈ 135 K. An anti-ferrimagnetic moment of ≈0.4 μB was determined from magnetization vs. applied field measurements. Temperature dependent impedance spectroscopy (IS) indicated 3 dielectric relaxation processes: electrode interface, grain boundary and bulk. The intrinsic bulk activation energy was found to be 0.27 eV and the dielectric permittivity ɛr was ≈23 in excellent agreement with Clausius–Mossotti predictions and showed no perceptible temperature dependence. This and the low ɛr value suggested that ErCrO3 is a dielectric rather than ferroelectric compound. IS measurements with applied dc bias revealed the signs of an unconventional type of Schottky barrier at the metallic Au electrode/ceramic ErCrO3 interface.Item Microwave-assisted synthesis of thermoelectric oxides and chalcogenides(Ceramics International, 2022) González-Barrios, Marta María; Tabuyo Martínez, Marina; Cascos Jiménez, Vanessa Amelia; Durá, Óscar Juan; Alonso, José Antonio; Ávila Brande, David; Prado Gonjal, Jesús De La PazThe combination of microwaves with other classical synthetic methods may be considered as a powerful tool for the preparation of metal oxides and metal chalcogenides. This approach allows the modification of the reaction kinetic significantly by shortening the processing time to minutes and it minimizes the energy consumption during the synthesis. In this work, potential thermoelectric compounds, which enable the direct conversion of temperature gradients into useful electric energy, have been produced by means of microwave-chemistry routes. Pure phases of SnS1-xSex (x = 0, 0.2, 1) have been synthesized in just 1 min by using microwave-hydrothermal synthesis. Moreover, Zn0.98M0.02O (M = Al, Ga) rods were formed by microwave-coprecipitation method in 5 min. Besides, 8 min of microwave-heating were enough for the combustion of Sr1-xLaxTiO3-δ (x = 0, 0.05, 0.1). In all cases, the utilization of microwave radiation produces high-quality phases. A comprehensive study of the structural, microstructural and thermoelectric properties of the microwave-synthesized materials is here performed by means of X-ray diffraction, SEM, HRTEM and temperature dependence measurements of Seebeck coefficient, electrical conductivity and thermal conductivity.Item Microwave-assisted synthesis and characterization of new cathodic material for solid oxide fuel cells: La0.3Ca0.7Fe0.7Cr0.3O3−d(Ceramics International, 2015) Molero-Sánchez, Beatriz; Prado Gonjal, Jesús De La Paz; Ávila Brande, David; Birss, Viola; Morán Miguélez, EmilioIn this work, we examine the benefits of alternative powder processing methods, with a primary focus on microwave-based synthesis, that could both lower material manufacturing costs and further enhance cathode performance for solid oxide fuel cell applications. La0.3Ca0.7Fe0.7Cr0.3O3−δ (LCFCr), formed using conventional solid-state methods, has been shown in earlier work to be a very promising catalyst for the oxygen reduction reaction. To further increase its performance, microwave methods were used to increase the surface area of LCFCr and to decrease the synthesis time. It was found that the material could be obtained in crystalline form in only 7 h, with the synthesis temperature lowered by roughly 300 °C as compared to conventional methods.Item The intercalation chemistry of H2V3O8 nanobelts synthesised by a green, fast and cost-effective procedure(Journal of Power Sources, 2013) Prado Gonjal, Jesús De La Paz; Molero-Sánchez, Beatriz; Ávila Brande, David; Morán Miguélez, Emilio; Pérez-Flores, Juan Carlos; Kuhn, Alois; García Alvarado, FlavianoH2V3O8 nanobelts have been successfully synthesised from commercial V2O5 powder through a fast and environmental friendly microwave-hydrothermal method. X-ray diffraction, field-emission scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy, high-resolution transmission electron microscopy and ICP spectroscopy were used to characterise the morphology and structure–microstructure details. Nanobelts about 100 nm wide and several micrometres long are easily prepared in no more than 2 h. The electrochemical study reveals the reversible insertion of ca. 4 Li per formula unit (400 mAh g−1), through several pseudo-plateaus in the 3.75–1.5 V vs Li+/Li voltage range showing the interest of this material produced by a “green” route as an electrode for lithium rechargeable batteries. After the first cycle a significant capacity loss is observed, though a high capacity, ca. 300 mAh g−1, remains upon cycling. Furthermore, the similarity of discharge and charge curves, pointing to the absence of hydrogen displacement during lithium insertion in H2V3O8, shows that not all protonated systems must be discarded as prospective electrode materials. On the other hand, further reduction down to 1 V is possible to insert up to 5 Li per formula unit (480 mAh g−1). Interestingly it corresponds to full reduction of vanadium to V3+ as it is also confirmed by EELS experiments. However, the full reduction to V3+ is associated with a fast decay of the extra capacity developed at low voltage with increasing current rate. Then for practical use we may consider only the capacity obtained down to 1.5 V.