Controlling the domain size to enhance the piezoelectricity of BiFeO 3 –BaTiO 3 via heterovalent doping

We demonstrate a novel concept of domain engineering to simultaneously achieve outstanding piezoelectricity ( d 33 ∼ 191 pC N −1 ) and high Curie temperature ( T C ∼ 485 °C) in BF ceramics by adding elements with high valence difference. It is revealed that the NaTaO 3 additive contributes to tuning the relaxor characteristics and the configuration of macrodomains and nanodomains in the nonergodic state (0.725- x )Bi 1.05 FeO 3 –0.275BaTiO 3 - x NaTaO 3 –0.3% MnO 2 , leading to heterogeneous domain structures with rhombohedral-tetragonal phase coexistence. In addition, temperature-dependent piezoelectric characterization studies exhibit a continually increasing d 33 with the increase of temperature in this system, and an ultrahigh piezoelectric constant ( d 33 = 516 pC N −1 ) can be found at the composition of x = 0.008 when the temperature reaches 320 °C. Combined with in situ XRD and first-principles calculations, we confirm that the enhancements of d 33 and P r in the BF–BT ceramics during the heating process have an intrinsic contribution from the phase transition of R 3 c to R 3 m . This work not only provides a concept to obtain ceramics with both excellent piezoelectricity and Curie temperature but also helps understanding the intrinsic origin of unusual high-temperature d 33 in BF–BT-based materials, which is useful for further developing BF-based piezoelectric materials.