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Obtaining coatings on metallic substrates of irregular geometries is not easy by traditional methods. In those cases electrochemical methods show important advantages and have been used successfully. To date only silver has shown to be inert with respect to superconducting cuprates, although progress has been made in the development of intermediate buffer layers. However, in the particular case of YBa2Cu3O7 , annealing above the cuprate superconducting melting point to attempt densification or texturing is hard on silver because of the lower melting point of the metal. . Focalized heating of superconducting oxides over metallic substrates, using LASER techniques on controlled geometries, allows densification of coatings. The Laser processed sample may be amorphous but the crystallinity is easily recovered, as well as the optimal oxygen content for the oxide, but the preferential orientation induced by the electrophoretic deposition is lost upon the recrystallization process occurring over polycrystaline substrates.La realización de depósitos de óxidos superconductores sobre substratos metálicos de geometría compleja y en general policristalinos está prácticamente basada en métodos electroforéticos o electroquímicos que permiten la utilización de un campo eléctrico de geometría definida para inducir el movimiento de partículas de óxido o de precursores de éste, hacia el electrodo elegido. Dichos métodos son fundamentales cuando el substrato es metálico o puede hacerse metálico con facilidad. Hasta el presente tan sólo la plata ha mostrado ser lo suficientemente inerte para permitir recocidos posteriores, aunque se está progresando en el desarrollo de capas “buffer”. Sin embargo, cuando el óxido depositado es YBa2Cu3O7 , el proceso de recocido posterior no permite la obtención de textura sobre Ag mediante métodos térmicos dado el inferior punto de fusión de este metal. El presente trabajo presenta un estudio de fusión zonal por láser que permite recocer el óxido sin fundir el substrato metálico de plata. El control de las distintas variables permite llegar a una solución en la que se puede preservar la naturaleza superconductora del depósito y su densificación. Ello requiere un tratamiento térmico posterior que recupera la cristalinidad y el contenido óptimo de oxígeno. Sin embargo, el tratamiento disminuye la orientación preferencial de las partículas de YBa2Cu3O7 que se obtiene mediante la deposición electroforética.

The first silver-copper mixed oxide was recently synthesized in our laboratory. Such synthesis has been possible using soft chemistry methods and low temperatures, which prevent the decomposition of silver oxides. The present work describes the electrochemical behaviour of the silver-copper mixed oxide, Ag2Cu2O3, as studied by cyclic voltametry and electrolysis, both for oxidation and for reduction reactions. This compound undergoes several redox processes when it is reduced, yielding metallic silver and metallic copper as final products. The initial oxide is not regenerated upon re-oxidation. On the other hand, when Ag2Cu2O3 is oxidized a new phase with stoichiometry Ag2Cu2O4±δ appears.The original compound can be regenerated after a new reduction.Recientemente se ha sintetizado en nuestro laboratorio el primer óxido mixto de cobre y plata. Tal síntesis ha sido posible gracias a la utilización de métodos de química suave y baja temperatura, que impiden que los óxidos de plata se descompongan. En este trabajo se describe el estudio llevado a cabo sobre el comportamiento electroquímico del óxido mixto de cobre y plata, Ag2Cu2O3 ,mediante voltametría cíclica y electrólisis tanto para los procesos de oxidación como de reducción. Dicho compuesto sufre varios procesos redox cuando es reducido, obteniéndose plata metálica y cobre metálico como productos finales, sin que se dé regeneración del óxido al volver a oxidar a éstos. En cambio al ser oxidado el Ag2Cu2O3, se observa la formación de una fase oxidada de estequiometría Ag2Cu2O4±δ a partir de la cual se puede regenerar el compuesto original.

The analysis of the electronic structure of the isolated silver copper oxide Ag2Cu2O4 is presented along with its precursor Ag2Cu2O4 and similar binary oxides, Ag2O, AgO, CuO, and NaCuO2. The results for AgCu2O4 reveal an electronic distribution in which silver and copper share a delocalized valence scheme with both metals in formal oxidation states larger than the usual Ag(super I) and Cu(super II).

The encapsulation of magnetic clusters of the transition metal ions between diamagnetic fragments of metal oxides is a major characteristic of polyoxometalate complexes. The reaction of divalent metal ions with the trivalent tungstophospate ligands produces new types of compounds. These compounds are derived from the Keggin and Dawson-Wells polyoxoanions. The tetrametallic unit M4O16 is encapsulated by the individual polyoxometalate entities.

Crystals of a heteropolytungstate compound with the formula K5.5Na1.5(PW10Cu2 H2O 2O38).13H2O were subjected to X-ray diffraction, magneticsusceptibility and electronparamagnetic resonance spectroscopy examinations. Structural data identified the predominant alpha-Keggin coordination taken by the compound and the location of the copper ions. In addition, the exchange-coupled copper pairs, which were confirmed using magnetic measurements, formed two different exchange interactions and two anisotropies for the compounds.

The structure and redox properties of the reduced Keggin complex, PMo12O40(VO)2](super 5-), were assessed using the density functional calculations (DFT). The redox properties of the metal oxide complex clusters were investigated through the relative stabilities of the reduced species as a function of the number n of the metal electrons. The complex's six out of the eight d electrons were contained in the three symmetric molybdenum orbitals while the two d electrons were at the vanadium orbitals.

Yttrium aluminate (Y3A5O12) was doped with different rare earth ions (i.e. Gd3+, Ce3+, Eu3+ and/or Tb3+) in order to obtain phosphors (YAG:RE) with general formula,Y3-x-aGdxREaAl5O12 (x = 0; 1.485; 2.97 and a = 0.03). The synthesis of the phosphor samples was done using the simultaneous addition of reagents technique. This study reveals new aspects regarding the influence of different activator ions on the morpho-structural and luminescent characteristics of garnet type phosphor. All YAG:RE phosphors are well crystallized powders containing a cubic-Y3Al5O12 phase as major component along with monoclinic-Y4Al2O9 and orthorhombic-YAlO3 phases as the impurity. The crystallites dimensions of YAG:RE phosphors vary between 38 nm and 88 nm, while the unit cell slowly increase as the ionic radius of the activator increases. Under UV excitation, YAG:Ce exhibits yellow emission due to electron transition in Ce3+ from the 5d level to the ground state levels (2F5/2, 2F7/2). The emission intensity of Ce3+ is enhanced in the presence of the Tb3+ ions and is decreased in the presence of Eu3+ ions due to some radiative or non-radiative processes that take place between activator ions. By varying the rare earth ions, the emission colour can be modulated from green to white and red. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]