Nanocrystalline BaAl2O4 powders prepared by aqueous combustion synthesis

In order to achieve BaAl2O4 formation via combustion synthesis, two types of recipes were designed: single fuel recipes (urea, glycine, β-alanine or hexamethylenetetramine) and innovative fuel mixture recipes (urea+glycine, urea+β-alanine and urea+hexamethylenetetramine respectively). No combustion reactions were noticed in the case of single fuel recipes based on urea or hexamethylenetetramine. The only crystalline phase present in the case of the powders obtained in such a way was unreacted Ba(NO3)2. Glycine and β-alanine generated smoldering reactions, leading to the formation of black powders, which consist of Ba(NO3)2, BaCO3 and traces of BaAl2O4 (in the case of β-alanine). Fuel mixture recipes proved to be better than single fuel recipes, yielding BaAl2O4 as main crystalline phase. The specific surface area of the resulted powders ranges between 2.0 and 3.9 m2/g. The urea and glycine fuel mixture was the most efficient yielding BaAl2O4 with an average crystallite size of 60 nm.