Piezoelectric properties of mechanochemically processed 0.67BiFeO₃-0.33BaTiO₃ ceramics

Solid solutions of BiFeO3 and BaTiO3 are promising lead-free piezoelectric materials, especially around the morphotropic phase boundary at 0.67BiFeO3-0.33BaTiO3. Still, these materials are challenged by phase instability and limited understanding of the processing-properties relationship. Here, we investigate mechanochemical activation and the use of BaTiO3 as seed particles for the 0.67BiFeO3-0.33BaTiO3 phase.

Contrary to expectations from seeding in lead-based perovskites, the BaTiO3 seeds do not promote the 0.67BiFeO3-0.33BaTiO3 perovskite phase neither during the mechanochemical activation nor the subsequent sintering, but cause an inhomogeneous structure with remnant BaTiO3. This results in ceramics with weaker low-field piezoelectric response than that of the unseeded route, but with higher field-induced strain, even up to 150 °C.

Both routes produce ceramics of high density and without significant secondary phases visible by X-ray diffraction. This demonstrates the advantage of mechanochemical activation and the possibility to tailor the piezoelectric response of 0.67BiFeO3-0.33BaTiO3 through the processing route.