TiO2-nonstoichiometry dependence on piezoelectric properties and depolarization temperature of (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

(Bi0.5Na0.5)0.94Ba0.06TixO1+2x lead-free piezoceramics with x varying from 0.97 to 1.03 were fabricated and characterized in order to investigate the effects of TiO2-nonstoichiometry on the piezoelectric properties and depolarization temperature of (Bi0.5Na0.5)0.94Ba0.06TiO3 composition. X-ray diffraction (XRD) analysis showed that all samples have a single phase of perovskite structure with rhombohedral symmetry. Piezoelectric and dielectric measurements revealed that deficiency of TiO2 leads to an increase in the piezoelectric coefficient (d33), free relative permittivity (ε33T/ε0), and loss tangent (tan δ) besides an increase in the electromechanical coupling coefficient (kp) within a certain amount, while excess of TiO2 results in a decrease in kp, d33, and ε33T/ε0, but an increase in tan δ. Depolarization temperature (Td) measurement indicated a decrease and an increase in Td as a result of increasing TiO2 deficiency and TiO2 excess, respectively. This TiO2-nonstoichiometry also induced changes in the remanent polarization (Pr) and coercive field (Ec) of the ceramics.