Colossal dielectric constant up to GHz at room temperature
  The search for new materials with extremely high ("colossal") dielectric constants, required for future electronics, is one of the most active fields of modern materials science. However, the applicability of the colossal-epsilon' materials, discovered so far, suffers from the fact that their dielectric constant, epsilon', only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of La15/8Sr1/8NiO4 surpass those of other materials. Especially, epsilon' retains its colossal magnitude of >10000 well into the GHz range. This material is prone to charge order and this spontaneous ordering process of the electronic subsystem can be assumed to play an important role in the generation of the observed unusual dielectric properties. 
S. Krohns, P. Lunkenheimer, Ch. Kant, A.V. Pronin, H.B. Brom, A.A.   Nugroho, M. Diantoro, A. Loidl