Abstract

GUSTAVO VALDERRAMA et al. Caracterización de perovskitas la_1-xsr_xnio₃ y la_2-2xsr_2xnio_4-d obtenidos a partir del método de auto-combustión. INCI [online]. 2005, vol.30, n.6, pp.25-33. ISSN 0378-1844.

The auto-combustion method was used to synthesize a series of La_1-xA_xNiO₃ perovskite type oxides where the La³⁺ cation is partially substituted by Sr²⁺and Mg²⁺. The X-ray diffraction analysis indicates that Sr has a strong effect on the structure of the synthesized solids producing a single perovskite type structure for x£0.1, while a mixture of spinella type oxides and NiO phases were observed for x³0.2. It is observed that the formal oxidation state of Ni decreases from 3+ (x= 0) to 2.6+ (x= 0.4), indicating that Sr enhances the reduction of the cations by promoting the electron acceptance capacity of the perovskite. No perovskite type structure was obtained with Mg. The temperature program reduction studies (TPR) showed that the reduction proceeds through a step wise process to form NiO, SrO and La₂O₃ phases which could be related to the activity presented in later catalytic studies of these precursor solids.

Keywords : Auto-combustión ; Caracterización ; Especies Intermediarias ; Perovskitas .