Record-breaking electrostrain in NaNbO3-based antiferroelectric ceramics via achieving fully reversible phase transition

Abstract

Antiferroelectric (AFE) materials hold great potential for actuation applications requiring high electrostrains, because of their reversible electric-field-induced AFE and ferroelectric (FE) phase transition. However, pure NaNbO₃ AFE ceramic usually presents a butterfly-shaped strain-electric field (S-E) curve with a small maximum strain (S_m) and a large negative strain (S_neg) under high electric field. Up to date, achieving a fully reversible high S_m in NN-based AFE ceramics has not been successful. Herein, a novel strategy of decreasing electronegativity difference was proposed to modulate the reversible AFE-FE phase transition, by deliberately introducing a dopant with low electronegativity difference, namely, Bi(Mg_1/3Al_1/3Ti_1/3)O₃ into 0.8NaNbO₃–0.2AgNbO₃. Consequently, a record reversible S_m of 0.45 %, free of S_neg, was successfully achieved in 0.75NaNbO₃–0.2AgNbO₃–0.05Bi(Mg_1/3Al_1/3Ti_1/3)O₃ ceramic, about 4.5 times higher than that of pure NaNbO₃ ceramic, together with appropriate frequency and thermal stabilities. Rietveld refinement of XRD demonstrated the decrease of [BO₆] octahedral tilting angles and ionic displacements accounted for the reversible AFE and FE phase transitions. This work provides a promising approach for achieving high electrostain in NaNbO₃-based ceramics, advancing their practical application in electromechanical fields.