Synthesis of trimetallic heteronuclear Y[Fe1-xCox(CN)6]·nH2O complexes and characterization of their thermal decomposition products

DIEGO MAURICIO GIL; MARÍA CAROLINA NAVARRO; MARIA CRISTINA LAGARRIGUE; MARÍA INÉS GÓMEZ; RAÚL ERNESTO CARBONIO

Valparaíso

Congreso; SÓLIDOS 2009; 2009

Universidad Técnica Federico Santa María de Valparaíso

Perovskite - type oxides are promising materials for many kinds of applications such as materials for chemical sensors, electrodes for fuel cells, and catalisys [1, 2]. YMO3 (M=Fe, Co) exhibits interesting physical and chemical properties because of their ionic and electronic defects. These materials are widely used in magnetic materials, environmental monitoring application and in heterogeneous photocatalisys [3]. In general Perovskite ? type oxides have been prepared by the conventional solid reaction method using high temperature and intermediate grindings from the corresponding single oxides. We proposed the thermal decomposition of heteronuclear complexes for the preparation of the di-or tri- metallic oxides because the mixing of metal cations at the atomic level and with the desired stoichiometry of the metals in the heteronuclear complex allows lowering the synthesis temperature down to the range 500-800 ºC, producing high surface area and homogeneous materials [4, 5] and sometimes, polymorphs not obtainable at higher temperatures. Y[Fe1-xCox(CN)6].nH2O (0  x 1) as a precursor of perovskite ? type oxide was synthesized by mixing aqueous solutions of Y(NO3)3.6H2O and a solution of K3[Fe(CN)6] and K3[Co(CN)6] with stoichiommetric relations and was stirred with heating during one hour. The resulting precipitate was collected by filtration, washed with deionized water, and finally dried in a dry box with silica gel. The prepared Y[Fe1-xCox(CN)6].nH2O complexes were heated at different temperatures during 10 hours to obtain perovskite ? type oxides. In order to characterize the complexes and the decomposition products, their Powder X- ray diffraction (PXRD) patterns and IR spectra in the region of 400-4000 cm-1 were recorded. The thermal decomposition process was examined by TGA and DTA analysis, performed at a heating rate of 5 ºC/min in air. The crystal structure of Y[Fe1-xCox(CN)6] .nH2O and YFe1-xCoxO3 oxides were refined by Rietveld analysis using the FULLPROF program. The crystal system of the complexes was orthorhombic, space group (Cmcm) having n=4 and YFe1-xCoxO3 oxides crystallizes in the orthorhombic system, space group Pbnm. In YFe1-xCoxO3 oxides when x=0, YFeO3 hexagonal was formed at 700 ºC and a mixture of YFeO3 hexagonal and orthorhombic phases were found at 800 ºC. At 900 ºC, only orthorhombic phase was observed. For x=1 YCoO3 was formed at 950 ºC. The size and morphology of the particles was determined by scanning electron microscopy (SEM).