Colossal dielectric constants in La15/8Sr1/8NiO4

We report the results of dielectric spectroscopy on La15/8Sr1/8NiO4, performed in a broad temperature and frequency range. This material exhibits extremely high (colossal) dielectric constants ε'. Room-temperature values ε' > 104 are found, remaining colossal up to the GHz-regime, which is of high relevance for possible applications. The charge transport in La15/8Sr1/8NiO4 is found to be dominated by hopping conductivity. The material is prone to charge order, which can be assumed to play an important role in the generation of its unusual dielectric properties.