Microstructure, dielectric and ferroelectric properties of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (NBTB) and 0.05BiFeO3-0.95NBTB ceramics: Effect of sintering atmosphere

0.94Bi(0.5)Na(0.5)TiO(3)-0.06BaTiO(3) (NBTB) and 0.05BiFeO(3)-0.95NBTB (BF-doped NBTB) lead-free ceramics were prepared by solid state reaction method. The ceramics were sintered at 1180 degrees C for 2 h in O-2 and N-2. All ceramics exhibited a single phase of perovskite structure. Relative amount of tetragonal phase was related to the sintering atmospheres. Both grain size and shape were influenced by the sintering atmospheres. Sintering the ceramics in N-2 weakened their dielectric anomalies corresponding to the transition from ferroelectric phase to the so-called "intermediate phase". When the NBTB and BF-doped NBTB ceramics were sintered in N-2, their maximum dielectric Constant and the degree of diffuseness of the transition from the "intermediate phase" to paraelectric phase increased, but their Curie temperatures decreased. The difference in dielectric properties of the ceramics sintered in different atmospheres was closely related to the difference in oxygen vacancy concentration. The correlation between ferroelectric properties and sintering atmospheres is associated with a competing effect among oxygen vacancy concentration. A-site vacancy concentration and percentage of tetragonal phase. (C) 2010 Elsevier B.V. All rights reserved.