Sol-gel combustion synthesis of BNBT powders

Ba-modified bismuth sodium titanate with composition 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO(3) (BNBT) was prepared by a citrate nitrate sol-gel combustion method. The sol was obtained using barium acetate, bismuth nitrate, sodium nitrate and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (C/N) were considered for the sol production. The corresponding gels were fired at different temperatures (300, 400, 500 degrees C) in order to evaluate the conditions necessary to obtain the decomposition of the precursors and the formation of the pure BNBT perovskitic phase in a single step. The best conditions to obtain the desired phase are: (C/N) = 0.2, and combustion temperature of 500 degrees C. Ball milled powders were densified at a temperature 100 degrees C lower than the one generally used for powder produced with the conventional mixed oxide route. The electrical properties are comparable to those reported for conventionally prepared materials.