Abstract
We studied frequency and temperature dependences of impedance, electric modulus, and dielectric permittivity of in the ranges of and , respectively. We first observed two electrical responses in the impedance and modulus formalisms. Then we detected a Debye-like relaxation in the permittivity formalism. Most interestingly, we found that the large dielectric constant of is independent of the temperature and frequency below . The results are interpreted in terms of a two-layer model with conducting grains partitioned from each other by poorly conducting grain boundaries. Using this model, we attributed the two electrical responses in impedance and modulus formalisms to the grain and grain-boundary effects, respectively, while the detected Debye-like relaxation and large dielectric constant were well explained in terms of Maxwell-Wagner relaxation.
4 More- Received 5 November 2003
DOI:https://doi.org/10.1103/PhysRevB.70.144106
©2004 American Physical Society