A CHEMICAL ROUTE FOR THE PREPARATION OF NANOSIZED RARE EARTH PEROVSKITE-TYPE OXIDES FOR ELECTROCERAMIC APPLICATIONS

ABSTRACT

This paper reviews the work performed by the authors on the preparation of LnTO₃ (Ln = rare earth elements, and T = transition metals) perovskite-type oxides by the thermal decomposition at low temperatures of the corresponding heteronuclear complexes. Bimetallic complexes in the series Ln[Fe(CN₆)]·nH₂O and Ln[Co(CN₆)] nH₂O, with Ln = from La through Yb, and trimetallic complexes in the series Ln¹ _xLnnl-x[Co(CN₆)] nH₂O and Ln[FeyCo1-_y(CN₆)] nH₂O were prepared. The formation of the perovskite-type oxides by the thermal decomposition of the complexes has been studied by simultaneous thermogravimetric and differential thermal analysis (TG/DTA), x-ray fluorescence (XRF), Fourier transform infrared (FTTR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The composition and temperature limits of stability for the dimetallic and trimetallic perovskite-type oxides have been clarified. The major role played by the ionic radii of the Ln3⁺ and T3⁺ ions on the formation of the perovskite-type oxides has been identified. Homogeneous perovskite-type oxide powders with nanosized particles, which possess promising characteristics for their applications as functional ceramics, are easily synthesized with this method.