Dielectric properties of the low dimensional vanadium oxides Ba2V3O9 and Sr2V3O9

The dielectric response of the low-dimensional vanadium oxides Ba2V3O9 and Sr2V3O9 has been investigated in the frequency range of 20 Hz–1 MHz. At low frequencies the dielectric response is governed by strong relaxation-like features, which we attribute to Maxwell–Wagner type contact contributions. The analysis of the complex dielectric spectra in terms of an equivalent circuit revealed the intrinsic dielectric constant and dc conductivity of these systems. The frequency-dependent ac conductivity in both systems follows the universal dielectric response behaviour, clearly indicating that hopping of localised charge carriers is the dominating charge-transport process. Also, a newly observed dielectric relaxation process in both systems is reported and we find evidence for a phase transition close to 455 K in both materials.