Effects of Bi nonstoichiometry in (Bi0.5+xNa) TiO3 ceramics

Effects of Bi nonstoichiometry on (Bi0.5+xNa) TiO3 (BNT) ceramics were investigated at x=-1+2 mol % of Bi-0.5 covering Bi deficiency and excess. At all compositions, rhombohedrally symmetric BNT perovskite formed without secondary phases. Increasing x caused smaller grains. Higher piezoelectric coefficient (d(33)) but lower depolarization temperature (T-d) occurred at Bi excess than at Bi deficiency and vice versa. Leakage current at room temperature decreased with decreasing x. Electrical conductivity of the stoichiometric BNT (x=0) from 700 to 900 degrees C increased with decreasing partial oxygen pressure from 1 to 10(-5) atm suggesting n-type conductivity at elevated temperatures. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3525370]