Synthesis, structure and luminescence of Er3+-doped Y3Ga5O12 nano-garnets

A novel Y3(1-x)Er3xGa5O12 nanocrystalline garnet has been synthesized by a sol-gel technique and a complete structural, morphological, vibrational, and optical characterization has been carried out in order to correlate the local structure of the Er3+ ions with their optical properties. The synthesized nanocrystals are found in a single-phase garnet structure with an average grain size of around 60 nm. The good crystalline quality of the garnet structure is confirmed by FTIR and Raman measurements, since the phonon modes of the nano-garnet are similar to those found in the single crystal garnet. Under blue laser excitation, intense green and red visible and 1.5 mu m infrared luminescences are observed, whose relative intensities are very sensitive to the Er3+ concentration. The dynamics of these emissions under pulsed laser excitations are analyzed in the framework of different energy transfer interactions. Intense visible upconverted luminescence can be clearly observed by the naked eye for all synthesized Er3+-doped Y3Ga5O12 nano-garnets under a cw 790 nm laser excitation. The power dependency and the dynamics of the upconverted luminescence confirm the existence of different two-photon upconversion processes for the green and red emissions that strongly depend on the Er3+ concentration, showing the potential of these nano-garnets as excellent candidates for developing new optical devices.This work has been partially supported by Ministerio de Ciencia e Innovacion of Spain (MICCIN) under The National Program of Materials (MAT2010-21270-C04-02; -03; -04), The Consolider-Ingenio 2010 Program (MALTA CSD2007-0045), and The National Infrastructure Program, by Ministerio de Economia y Competitividad of Spain (MINECO) within The Indo-Spanish Joint Programme of Cooperation in Science and Technology (PRI-PIBIN-2011-1153/DST-INT-Spain-P-38-11), and by the EU-FEDER funds (UCAN08-4E-008). S.F. Leon-Luis and V. Monteseguro wish to thank MICINN for the FPI grants (BES-2008-003353 and BES-2011-044596). Dr V. Venkatramu is grateful to DAE-BRNS, Government of India for the award of DAE Research Award for Young Scientists (no. 2010/20/34/5/BRNS/2223).Venkatramu, V.; León-Luis, SF.; Rodriguez-Mendoza, UR.; Monteseguro, V.; Manjón, FJ.; Lozano-Gorrín, AD.; Valiente, R.... (2012). Synthesis, structure and luminescence of Er3+-doped Y3Ga5O12 nano-garnets. Journal of Materials Chemistry. 22:13788-13799. doi:10.1039/c2jm31386cS13788137992

RE_0.01Sr_0.99Co_0.5Fe_0.5O₃ (RE = La, Pr, and Sm) Cathodes for SOFC

This study focuses on the synthesis, characterization, and study of new perovskite-type materials as cathodes in SOFC. The doped perovskites were successfully synthesized with high purity. The electrochemical performance of these materials was extensively examined through the characterization of I-V-P and EIS curves at the three temperatures, 750, 800, and 850 °C, where it reveals a substantial reduction in total resistances, accompanied by an impressive increase in power densities. The cell featuring La0.01Sr0.99Co0.5Fe0.5O3 exhibited the most commendable electrochemical properties at each temperature, following which were SrCo0.5Fe0.5O3, Pr0.01Sr0.99Co0.5Fe0.5O3, and Sm0.01Sr0.99Co0.5Fe0.5O3