INVESTIGADORES
MARTINEZ GARCIA Ricardo
congresos y reuniones científicas
Título:
Study of the crystal structure of some Ferrocyanide (II, III)
Autor/es:
RICARDO MARTÍNEZ GARCÍA; EDILSO REGUERA; MARCELO KNOBEL
Reunión:
Congreso; XVII Latin American Symposium on Solid State Physics; 2004
Resumen:
Hexacyanoferrates (II, III) have been intensively studied by its potential applications in nanotecnology. There are prototypes of de molecular magnetic materials with high Curie temperature [Entley et. al., 1995; Holmes et. al. 1999]. Others, have potentialities as adsorbents because they have a microporous structure [Cartraund et. al., 1981; Balmaseda et. al., 2002], and molecular sieves [Boxhoorn et. al., 1985]. Some of them are used in catalytic process [Kuyper and Boxhoorn, 1987; Reguera et. al., 1992], or in therapy of humans and animals affected by nuclear accidents [Roberts, 1987]. All these applications depend on the crystal structures of the compounds and these have not been totally studied. The crystal structure of some ferrocyanides (II, III), included the mixed compositions compounds, were determined. In the last case, the Na1+, K1+, and Cs1+ appear in the structure as charge balance cations. The studied compounds crystallize in two different systems, the ferricyanide in the cubic system, spatial group Fm-3m and the ferrocyanides of mixed compositions in the orthorhombic system, spatial group Pmn21. The ferricyanides have a structure with 33% of vacancies, these compounds are hydrated and, in its structure, there are two kinds of water molecules, coordinated and zeolitic waters. On the other hand, the ferrocyanides have a compact structure with few number of molecules of water and, in the case of the cesium mixed compounds, is anhydrous. The orthorhombic structure of the mixed ferrocyanides can be derivated from the cubic structure. In this work, we analyze the role of the alkaline ions in the deformation of the cubic cell. We also studied the ionic exchanges and the structural deformation that takes place when a ferrocyanide is in contact with a Cs1+ aqueous solution. The determination of the different structures were done from powder X-ray diffraction patterns and using the Rietveld method. We used the infrared and Mössbauer spectroscopy, termogravimetry, and the water adsorption curves that support the structural determination and favor the interpretation of the results.