Person:
García Fernández, Javier

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First Name
Javier
Last Name
García Fernández
URI
https://hdl.handle.net/20.500.14352/81313
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Universidad Complutense de Madrid
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20202
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Author: Martínez Casado, Ruth × Has files: true ×

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    New insights into the luminescence properties of a Na stabilized Ga-Ti oxide homologous series
    (Journal of materials chemistry C, 2020) García Fernández, Javier; García Carrión, Marina; Torres Pardo, Almudena; Martínez Casado, Ruth; Ramírez Castellanos, Julio; Nogales Díaz, Emilio; González Calbet, José María; Méndez Martín, Bianchi
    Herein, we achieve the synthesis and structural study of a luminescent Na-stabilized Ga-Ti oxide homologous series by atomically resolved electron microscopy. Relevant optical properties as a function of the titanium content have been revealed. In particular, the excitation and emission bands change with the series term, showing wide tunability of the luminescence bands, ranging from the ultraviolet to the infrared. First principles studies of these structures have been done in the framework of density functional theory (DFT) to understand the optical properties. Good agreement with the experimental measurements for the three synthesized terms has been obtained from the perspective of the composition and occupancy of the crystallographic sites, as well as from the energy band structure point of view. This work paves the way to explore further the capabilities of tuning the electronic and optical properties in a variety of application fields.
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    Influence of cation substitution on the complex structure and luminescent properties of the Zn_kIn_2O_(k+3) system
    (Chemistry of materials, 2020) García Fernández, Javier; Torres Pardo, Almudena; Bartolomé Vílchez, Javier; Martínez Casado, Ruth; Zhang, Qing; Ramírez Castellanos, Julio; Terasaki, Osamu; Cremades Rodríguez, Ana Isabel; González Calbet, José María
    The effect of In^(3+) substitution by Ga^(3+) or Al^(3+) on the structure and luminescent properties of Zn_7In_(2-x)M_xO_10 (M = Ga or Al; 0 <= x <= 1) oxides has been investigated by means of high spatial resolution X-ray spectroscopy and high-angle annular dark-field images, combined with magic angle spinning nuclear magnetic resonance spectroscopy. Local structural variations have been identified for the Al- and Ga-doped samples through the analysis of atomically resolved chemical maps and the identification of their structural environment within the wurtzite lattice. In3+ is distributed in a zig-zag modulation, while Al^(3+) and Ga^(3+) are located in a flat distribution at the center of the wurtzite block. Density functional theory calculations provide unambiguous evidence for the preferential flat location of Ga^(3+) and Al^(3+) associated with the different strains introduced in the structure as a result of their ionic radii. The characterization of the photoluminescence response reveals the appearance of new radiative recombination pathways for the doped materials because of the presence of new defect levels in the band gap of the Zn_7In_2O_10 structure.