Person:
Prado Gonjal, Jesús De La Paz

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First Name
Jesús De La Paz
Last Name
Prado Gonjal
URI
https://hdl.handle.net/20.500.14352/76087
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Inorgánica
Area
Química Inorgánica
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2020 - 20222
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Start date: 2020 × Subject: 538.9 ×

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    Structural and dielectric properties of ultra-fast microwave-processed La_0.3Ca_0.7Fe_0.7Cr_0.3O3-delta ceramics
    (Journal of solid state chemistry, 2022) Sánchez Ahijón, Elena; Schmidt, Rainer; Martínez De Irujo Labalde, Xabier; Haris Masood, Ansari; Fernández Díaz, María Teresa; Morán, Emilio; Molero Sánchez, Beatriz; Prado Gonjal, Jesús De La Paz
    Perovskite La_0.3Ca_0.7Fe_0.7Cr_0.3O_(3-delta) (LCFCr) is a mixed ionic and electronic conductor (MIEC) that can be employed as an electrode material in reversible solid oxide fuel cells (RSOFCs). In this work, an ultra-fast (15 min) one-step microwave (MW)-assisted combustion synthesis route has been developed to obtain phase pure and highly crystalline LCFCr powder. The synthesized powders exhibited a sponge-like microstructure with increased electrochemical reaction sites. Neutron thermodiffraction analysis revealed a structural transition above 500 degrees C from the room temperature (RT) orthorhombic Pnma to a rhombohedral R3c perovskite phase. The oxygen vacancy concentration was found to increase from delta = 0.272(7) at RT to delta = 0.333(5) at 900 degrees C. Furthermore, a 3-dimensional G-type antiferromagnetic structure was detected at RT. MW-sintering of pressed green ceramic pellets was carried out at 950 degrees C for 1 h, using a MW-transparent quartz fiber crucible or alternatively a SiC crucible acting as a MW-absorber. Impedance spectroscopy data on sintered ceramic pellets revealed electronic inhomogeneity as demonstrated by the occurrence of three dielectric relaxation processes associated with two grain boundary (GB)-like contributions and one bulk. The dielectric inhomogeneity encountered may be restricted to the extrinsic GB areas, which may be rather thin. More homogeneous dielectric properties of the GBs were found in the pellet that was sintered in the SiC crucible.
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    From theory to experiment: BaFe0.125Co0.125Zr0.75O3-delta, 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, Emilio; Schmidt, Rainer; Prado Gonjal, Jesús De La Paz
    In a recent theoretical study [Jacobs et al., Adv. Energy Mater., 2018, 8, 1702708], BaFe0.125Co0.125Zr0.75O3-delta 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 Pm3m 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 x 10(-6) K-1 suggests acceptable compatibility with common electrolytes. Electrochemical impedance spectroscopy of symmetrical cells gives an area-specific resistance of 0.33 Omega cm(2) at 700 degrees C and 0.13 Omega cm(2) at 800 degrees C. These values are reduced to 0.13 Omega cm(2) at 700 degrees C and 0.05 Omega cm(2) at 800 degrees C when the material is mixed with 30 wt% Ce0.9Gd0.1O2-delta.