A structural perspective on the origin of the anomalous weak-field piezoelectric response at the polymorphic phase boundaries of (Ba, Ca)(Ti, M)O3 lead-free piezoelectrics

In this paper, we compare the structural features of Ca modified Ba(Ti, Sn)O3 with that of its Ca-free counterpart to understand why the Ca-modified variant of this lead-free piezoelectric gives a much higher piezoelectric response. We found that in spite of the reduced spontaneous lattice strain, the polarization of the Ca-modified variant is higher. We, therefore, demonstrate that the very large piezoelectric response of (Ba, Ca)(Ti, Sn)O3 is associated with the decoupling of the polarization and lattice strain by Ca-modification.