Mesoscopic dynamical coupling in A-site relaxor ferroelectrics

K1xLixTaO3 and Na1/2Bi1/2TiO3 belong to a class of material called relaxor ferroelectrics. They have the same pm3m structural symmetry as do perovskite (ABO3) ferroelectric systems in the cubic paraelectric phase. However, the disordered cation sites give rise to a frequency dependent dielectric dispersion. This is the dening characteristic of relaxor ferroelectrics. Another commonly observed feature is the formation of nano-sized local polar regions, the reorientations of which are related to the dielectric dispersion. In this thesis work, we use spectroscopic techniques to study the dynamical coupling eects in macroscopic excitations and resonances due to the nano-sized regions that share the same symmetry properties.