Comparative study on heterophase structures in ferroelectric solid solutions based on barium titanate

Heterophase structures are first compared for related perovskite-type ferroelectric solid solutions that are tin-modified barium titanate and hafnium-modified barium titanate with compositions near the morphotropic phase boundary. The studied heterophase structures are interpreted in terms of two models wherein two polydomain phases and a single-domain interlayer or polydomain and single-domain phases and a polydomain interlayer coexist at the complete stress relief. The role of the non-180 degrees domain types and unit-cell parameters of the coexisting phases is highlighted to show the important link between the phase contents and unit-cell parameters near the morphotropic phase boundary. A link between the heterophase/polydomain regions and piezoelectric activity of the ferroelectric solid solutions is discussed. Results on the phase contents in the morphotropic region are consistent with experimental data on the aforementioned solid solutions based on barium titanate