Bismuth sodium titanate(BNT)ceramics exhibit outstanding strain responses but are unfavorable for application in high-sensitivity displacement actuators due to the large negative strain resulting from irreversible changes in their phase transition and domain structure.Here,(1−x)Bi_(0.50)Na_(0.41)K_(0.09)TiO_(3)-xNaNbO_(3)(BNKT−xNN)solid solutions were prepared to improve the strain properties through the strategy of modulating the phase boundary and domain structures.The introduction of sodium niobate could effectively regulate the relative content of the tetragonal(P4bm)and rhombohedral(R3c)phases in the phase boundary region.The ferroelectric-to-relaxor phase transition(T_(F−R))was reduced,and the ergodic relaxor(ER)state was nurtured at room temperature.Excellent zero-negative strain properties of S=0.41%and d_(33)^(*)=742 pm/V were achieved from the reversible transition between the ER and ferroelectric states under an applied electric field(x=0.04).Additionally,understanding the domain states via piezoelectric force microscopy(PFM)and firstorder reversal curve(FORC)revealed that the superior strain responses originated from the reversible inter-transformation of substable macrodomains and polar nanoregions(PNRs)in the phase boundary.This study provides new insight into the interplay between the evolution of phase boundaries and domain structures and the strain properties of BNT-based ceramics.
Dielectric capacitors,as physical powers,are critical components of advanced electronics and pulse power systems.However,achieving high energy efficiency without sacrificing recoverable energy density remains a challenge for most dielectric materials.In this work,the aliovalent Sm^(3+)doped Ba_(0.12)Na_(0.3)Bi_(0.3)Sr_(0.28)TiO_(3)(BNBST)relaxor ferroelectric at the A site was used to design a defect-induced phase/domain structure to improve polarization switching.A high energy efficiency of 91%,together with a recoverable energy density of 2.1 J/cm^(3),was achieved in Sm_(0.07)–BNBST ceramics at a low electric field of 114 kV/cm,exceeding those of other dielectric materials under the same electric field.In addition,Sm_(0.07)–BNBST ceramics exhibit good energy storage stability and endurance and fast charging‒discharging speeds,demonstrating their great potential in electrostatic capacitor applications.This work provides an approach to achieve highperformance dielectrics through aliovalent rare earth doping and builds a close relationship between the defect-engineered phase/domain structure and polarization switching for energy storage.
