Solution combustion synthesis (SCS) which includes the redox reaction between nitrates and organic fuels in solution is one of suitable methods for synthesis of oxide nanoparticles. In the present work, we investigated the SCS process in the Sr-Al-O system and found that it proceeds in the following stages. Stage 1 takes place just after evaporation of H2O but before start-up of combustion; stage 2: combustion reaction; stage 3: rapid cooling down to some temperature below that of furnace facilitated by vigorous evolution of gaseous products; and stage 4: warm-up to the furnace temperature. It has been found that Al(NO3)3 · 9H2O and CO(NH2)2 react at stage 1, while Sr(NO3)2 (whose decomposition temperature is about 925 K) react with Al(NO3)3 · 9H2O and CO(NH2)2 at stage 2 to give the nuclei of SrAl2O4. Upon completion of combustion, rapid cooling down caused by vigorous evolution of gases occurs at stage 3. The particles of newly formed SrAl2O4 did not grow significantly (20–50 nm) because of high temperature gradients. The particle sizes did not change meaningfully at stages 3 and 4, due to which the SCS process yielded fine SrAl2O4 nanoparticles (∼50 nm).
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