Combustion synthesis of Sr0.5Ba0.5Nb2O6 and effect of fuel on its microstructure and dielectric properties

Nano-sized Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} (SBN50) powder has been synthesized, at very short reaction time, for the first time by a novel combustion method. Ba(NO{sub 3}){sub 2} and Sr(NO{sub 3}){sub 2} were used as source of Sr and Ba, respectively, while Nb-oxalate was used as the source of niobium. Urea, hexamethyltetramine (HMT) and glycine were used as fuel. The crystallite sizes in the powder ranged between 14-125 nm. X-ray diffraction analysis showed complete SBN50 phase formation at 700 deg. C, when urea/HMT was used as fuel, and at 800 deg. C when glycine was used as fuel. Ferroelectric-paraelectric phase transition temperature (T{sub c}) close to 40 deg. C was observed when urea and HMT were used and the T{sub c} was -49 deg. C when glycine was used. When urea was used as fuel highest dielectric constant was observed for the pellets sintered at 1250 deg. C for 4 h. Low dielectric loss was observed when HMT was used as fuel. Larger grain sizes in the sintered pellets were observed when glycine was used as fuel.