Controlling the domain size to enhance the piezoelectricity of BiFeO3-BaTiO3via heterovalent doping

We demonstrate a novel concept of domain engineering to simultaneously achieve outstanding piezoelectricity (d(33) similar to 191 pC N-1) and high Curie temperature (T-C similar to 485 degrees C) in BF ceramics by adding elements with high valence difference. It is revealed that the NaTaO3 additive contributes to tuning the relaxor characteristics and the configuration of macrodomains and nanodomains in the nonergodic state (0.725-x)Bi1.05FeO3-0.275BaTiO(3)-xNaTaO(3)-0.3% MnO2, 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 degrees 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 R3c to R3m. 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.