Infrared and THz spectroscopy of nanostructured dielectrics

Results achieved using the infrared/THz spectroscopy of various inhomogeneous dielectrics in the Depart- ment of Dielectrics, Institute of Physics, Prague, during the last decade are briefly reviewed. The discussion concerns high-permittivity ceramics with inevitable low-permittivity dead layers along the grain boundaries, relaxor ferroelectrics with highly anisotropic polar nano-regions, classical matrix-type composites, core-shell composites, filled nanoporous glasses, polycrystalline and epitaxial thin films, heterostructures and superlat- tices on dielectric substrates. The analysis using models based on the effective medium approach is discussed. The importance of depolarizing field and of the percolation of components on the effective ac dielectric re- sponse and the excitations contributing to it are emphasized.