Citrate-nitrate auto-combustion synthesis of perovskite-type nanopowders: a systematic approach

Citrate-nitrate auto-combustion synthesis is used to prepare an iron, a cobalt and a cerium-perovskite. The influence of different synthesis conditions on the combustion process, phase composition, textural and morphological properties is studied in detail by X-ray diffraction, nitrogen adsorption and scanning electron microscopy. Results show that the combustion intensity increases from iron, to cerium, to cobalt-perovskite. Conversely, the combustion intensity decreases and thus the safety and the gain of the combustion process increase by using high fuel/oxidant ratios, low pH values or combustion reactors with high heat dispersion capacity. High fuel/oxidant ratios increase particle size and may enhance dopant segregation. Low citric acid/metal nitrates ratios may cause precipitation of the most insoluble compounds or segregation of the dopant. High citric acid/metal nitrates ratios increase the formation temperature of the perovskite-type structure. Low pH values are deleterious for the phase composition and/or for the morphology of the final product, although at high pH values dopant segregation may occur.