Effect of simultaneous substitution of magnesium and niobium on dielectric properties and phase transition temperature of bismuth sodium barium titanate ceramics

(Bi1/2 Na1/2)0.94Ba0.06Ti1−x (Mg1/3Nb2/3)xO3 ceramic samples with x = 0.0, 0.01, 0.05, 0.15, 0.20 were synthesized by solid state method. Microstructure, dielectric properties, impedance and conductivity of the ceramics were studied. Phase formation was confirmed by X-ray diffraction. Co-doping of the ceramics with Mg and Nb at x = 0.01 raised the dielectric constant from 6510 to 8225 at the frequency of 1 KHz. Further increase in (Mg1/3Nb2/3)4+ concentration up to 0.15 increased the transition temperature from 275 °C to 339 °C and lowered the dielectric constant. The ac impedance measurements showed a linear response with frequency at lower temperature indicating insulating behavior and a single semicircular arc with spike at higher temperature.