Polaron-assisted dielectric relaxation processes in donor-doped BaTiO3-based ceramics

TL;DR

This study investigates dielectric relaxation in Gd-doped BaTiO3 ceramics, revealing polaronic conduction mechanisms and how Gd doping influences activation energy and relaxation processes.

Contribution

It provides new insights into polaron-assisted dielectric relaxation and conduction mechanisms in Gd-doped BaTiO3 ceramics, combining experimental analysis with formal theoretical models.

Findings

Activation energy decreases with Gd doping from 0.29 to 0.21 eV.

Polaronic effects dominate conduction, involving Ti4+ and Ti3+ ions.

Small polaron hopping governs dielectric dispersion.

Abstract

Perovskite structure materials based on the Ba1-xGdxTiO3 system, where x = 0.001, 0.002, 0.003, 0.004 and 0.005, were prepared via the Pechini chemical synthesis route. The dielectric properties have been analyzed over a wide temperature and frequency range, revealing a significant contribution of the conduction mechanisms in the dielectric response of the studied ceramics. In fact, by using the Davidson-Cole formalism, the observed electrical behavior was found to be associated with relaxation processes related to intrinsic defects mobility promoted by a thermally-activated polaronic mechanism. The obtained values of the activation energy for the relaxation processes, estimated from the Arrhenius law for the mean relaxation time, revealed a decrease from 0.29 up to 0.21 eV as the Gd-doping concentration increases, which suggests the conduction process to be associated with the polaronic effects due to the coexistence of Ti4+ and Ti3+ ions in the structure. Analysis from the conductivity formalism, by using the Jonscher universal power-law, confirmed the polaron-type conduction mechanism for the dielectric dispersion, as suggested by the dielectric analysis, being the nature of the hopping mechanism governed by small polaron hopping (SPH) charge transport in the studied Ba1-xGdxTiO3 ceramics.