A series
of tungsten bronze Sr2Na0.85Bi0.05Nb5–x
Ta
x
O15 (SBNN-xTa) ferroelectric
ceramics were designed and synthesized by the traditional solid-phase
reaction method. The B-site engineering strategy was utilized to induce
structural distortion, order–disorder distribution, and polarization
modulation to enhance relaxor behavior. Through investigating the
impact of B-site Ta replacement on the structure, relaxor behavior,
and energy storage performance, this study has shed light on the two
main factors for relaxor nature: (1) with the increase of Ta substitution,
the tungsten bronze crystal distortion and expansion induced the structural
change from an orthorhombic Im2a phase to Bbm2 phase at room temperature; (2) the
transition from ferroelectric to relaxor behavior could be attributed
to the coordinate incommensurate local superstructural modulations
and the generation of nanodomain structure regions. Moreover, we benefited
from the effective decrease of ceramic grains and inhibition of abnormal
growth. Finally, we obtained an effective energy storage density (W
rec) ∼ 1.6 J/cm3, an efficiency
(η) ∼ 80%, a current density (C
D) ∼ 1384.2 A/cm2, and a power density (P
D) ∼ 138.4 MW/cm3.