The Dielectric Spectroscopy Laboratory in interested in complex relaxation behavior of ion inside ferroelectric lattices. The main goal of this particular research is dopant, for instance Cu ions inside a KTN lattice.  Here the mismatch in ionic radii results in a multiwall potential and the creation of a virtual dipole as the Cu ion moves between local troughs inside the multi well.  This oscillation can be cooperative as long range interactions between ions begin to dominate with the approaching ferroelectric transition. These interactions lead to thermal behavior reminiscent of glass forming liquids.  In the ferroelectric phase, the same ionic oscillation can become restricted due to the large internal fields present after the spontaneous polarization of the ferroelectric transition. Such confinement can find parallels in soft condensed matter physics.  Transport phenomena such an electron hopping is also visible in the dielectric landscape.  How the local environment modifies this behavior is a central theme of dielectric research, illuminating topics like Anomalous diffusion.  Phenomena such as percolation can also be observed whereby the accumulation of the local polarization vectors of individual clusters coalesces to an infinite percolation cluster.  A final theme in this multifaceted field is the design of smart materials based on a thorough understanding of their ferroelectric behavior.

 

Figure 4. The dielectric losses, ε”, for copper-doped KTN crystal. The three phase transitions are evident at T= 295.6 K, 291.1 K, and 230 K, respectively