(Bi0.5Na0.5)TiO3 ferroelectric ceramics: Achieving high depolarization temperature and improved piezoelectric properties.

(Bi 1/2 Na 1/2)TiO 3 -based materials have received much attention due to large electro-strain and high piezoelectric constant (d 33), but the tough issue is that the existence of inherent depolarization temperature (T d) limits the temperature stability and application temperature range. Previously, reports about the formation of BNT/oxide (i.e., ZnO, Al 2 O 3) composites thought that T d can be deferred to a higher temperature and then thermal depolarization improves. However, the deferred T d of BNT/oxide composites is limited, accompanied by a low d 33. Here, we design the {[Bi 0.5 (Na 0.8 K 0.2) 0.5 ] 1- x Pb x }TiO 3 ceramics, leading to a big shift of T d from 77 ℃ to 390 ℃. Large d 33 (140 pC/N) and high T d (∼263 ℃) can be simultaneously achieved for the sample with Pb=0.05, and T d could be further deferred higher (390 ℃) for Pb=0.20. The off-centre displacement of Pb induced by Pb-O hybridization in the PbO 12 polyhedron and ferroelectric order stabilized by the addition of Pb can provide the driving force to strengthen the ferroelectric order, and then promote the thermal stability. [ABSTRACT FROM AUTHOR]