Macroscopic response and directional disorder dynamics in chemically substituted ferroelectrics

Using temperature-resolved dielectric spectroscopy in the range 25–320 K we investigate the macroscopic response, phase symmetry, and order/disorder states in bulk ferroelectric K1−yLiyTa1−xNbx (KLTN). Four longrange symmetry phases are identified with their relative transitions. Directional analysis of the order/disorder states using Fr¨ohlich entropy indicates global symmetry breaking along the growth axis and an anisotropic dipolar effective thermodynamic behavior, which ranges from disordered to ordered at the same temperature for different directions in the sample. Results indicate that the macroscopic polarization, driven by nanosized polar regions, follows a microscopic perovskite eight-sites lattice model.