Combustion synthesis of Sr_(0.5)Ba_(0.5)Nb_2O_6 and effect of fuel on its microstructure and dielectric properties

摘要

Nano-sized Sr_(0.5)Ba_(0.5)Nb_2O_6 (SBN50) powder has been synthesized, at very short reaction time, for the first time by a novel combustion method. Ba(NO_3)_2 and Sr(NO_3)_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℃, when urea/HMT was used as fuel, and at 800℃ when glycine was used as fuel. Ferroelectric―paraelectric phase transition temperature (T_c) close to 40℃ was observed when urea and HMT were used and the T_c was ―49℃ when glycine was used. When urea was used as fuel highest dielectric constant was observed for the pellets sintered at 1250℃ 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.