Structure and dielectric properties of bismuth sodium titanate ceramic prepared by auto-combustion technique

(Bi0.5 Na0.5 )TiO3 ceramic was prepared by dry auto-combustion method using urea as a fuel. It was shown that the phase composition of the synthesized powder depends on the amount of urea. The X-ray diffraction study confirmed that single phase rhombohedral structure with space group R3C was obtained in the powder calcined at 700°C when 25 wt.% of urea was added, but secondary phases were observed with higher addition of urea. Pellets have been formed from the single phase powder and sintered at 1100°C for 2 and 3 hours. The effect of sintering conditions on the structural and dielectric behaviour was studied in detail. The scanning electron micrographs of pellets showed dense structure with well-defined rectangular grains having larger size after longer sintering time. The temperature and frequency dependence dielectric study of the sintered samples showed two dielectric peaks attributed to the factors caused by the phase transitions from ferroelectric to antiferroelectric and antiferroelectric to paraelectric phase. The dielectric constant and the diffuse phase transition behaviour increases with increase in sintering time.