The dielectric constant is a measure of the electrical polarizability of a material and the most important quantity in the construction of capacitive elements in electronics. Higher ε' allows for smaller dimensions of these elements. This is not only important for the further miniaturization of electronic circuits, but also can be used for the enhancement of the energy and power density of very large capacitors used instead of batteries for the short-term storage of energy, e.g., in hybrid cars. The capacitive materials employed in current electronics often have relatively low values of ε' of the order of 10.
Colossal dielectric constants are found in various materials and can be caused by different physical processes. Click the following links to learn more:
For a review about CDCs in transition-metal oxides and the different physical mechanisms leading to CDCs, see:
Colossal dielectric constants in transition-metal oxides
P. Lunkenheimer, S. Krohns, S. Riegg, S. G. Ebbinghaus, A. Reller, and A. Loidl, Eur. Phys. J. Special Topics 180, 61 (2010).