Improved Dielectric and Piezoelectric Response in Defect‐Mediated (Na _0.5 Bi _0.5 )TiO ₃ ‒BaAlO

ABSTRACT

Piezoceramics based on (Na _0.5 Bi _0.5 )TiO ₃ have garnered considerable attention over the past decade due to the remarkable properties observed near the morphotropic phase boundary (MPB). The piezoelectric response ( d ₃₃ ) is inversely related to the ferroelectric–relaxor ( T _F‐R ) or depolarization ( T _d ) phase transition temperature. It has been suggested that the introduction of oxygen defects can elevate the T _d while reducing the d ₃₃ . In contrast, our investigation on the (Na _0.5 Bi _0.5 )TiO ₃ ‒ x BaAlO _2.5 solid solution (via introducing oxygen defects) revealed a decrease in T _d and a corresponding increase in d ₃₃ , reaching a maximum of approximately ∼151 pC/N. This counterintuitive phenomenon has been linked to a notable increase in the number of interfaces or domain wall density, which compensates for a reduction in lattice structural distortion.