Piezoelectric properties of mechanochemically processed 0.67BiFeO3-0.33BaTiO3 ceramics
Gianni Ferrero, Konstantin Astafiev, Erling Ringgaard, Leonardo Soares de Oliveira, Bhaskar Reddy Sudireddy, Astri Bjørnetun Haugen, Katarina Žiberna, Barbara Malič, Tadej Rojac
Abstract
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.