Decoding the correlation between initial polarity and strain property of BNT-based ceramics

Although a large electric-induced strain has been obtained in sodium bismuth titanate (Bi 0.5 Na 0.5 TiO 3 , BNT)-based ceramics using chemical modifications, the effect of initial BNT-based ceramic's polarity on modulating strain properties was rarely reported. Herein, we comparatively studied the effect of tantalum (Ta) doping on two BNT-based ceramics with different ferroelectric polarities, namely, (Bi 0.5 Na 0.5 ) 0.935 Ba 0.065 TiO 3 –0.7%Bi 2 FeCrO 6 and (Bi 0.98 Gd 0.02 ) 0.5 Na 0.5 TiO 3 . The former locates at the morphotropic phase boundary (MPB), whereas the latter is close to pristine BNT ceramics. An effective critical point, located at the crossover between ferroelectric and relaxor, is constructed in the former ceramic and significantly enhances strain properties, whereas a useless one is found in the latter ceramic due to the retention of a non-ergodic relaxor and has merely limited ability to promote strain properties. Our results demonstrate that the ferroelectric polarity of the initial BNT-based ceramic matrix also plays an important role in pursuing high strain properties.