Colossal dielectric permittivity and mechanism of AC conduction in bulk delafossite CuFeO2

We report structural, dielectric, and ac conductivity studies of CuFeO2, a material that belongs to the delafossite family. X-ray diffraction, X-ray absorption near edge structure (XANES), and impedance studies were carried out in order to investigate the structural and dielectric properties of the system. XANES measurement suggests that Fe present in the sample is in a mixed valence state. Dielectric properties measured at a temperature range of 84-450 K exhibit colossal dielectric permittivity with clearly distinguishable grain and grain boundary contributions. It has been found that both short-range and long-range motions of charge carriers are present in the sample, with the short-range motion dominating at low temperatures and long-range motion dominating at high temperatures. It has also been observed that the conduction in the sample is dominated by the conduction through the grain boundaries. Published under license by AIP Publishing.