Sol-gel combustion synthesis of lead-free BNBT powders

Ba-modified bismuth sodium titanate with composition 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO3 (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°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°C. Ball milled powders were densified at a temperature 100◦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.