Effect of acceptor concentration on the bulk electrical conduction in acceptor (Mg)-doped BaTiO3

Abstract

Bulk electrical conductivity of acceptor (Mg)-doped BaTiO3 ceramics were evaluated via an impedance spectroscopy analysis for materials with Mg concentrations up to 0.6 mol % and over a temperature range of 120–540 °C. At high temperatures beyond 320 °C, the activation energies of the bulk electrical conduction (Eσ) slightly decreased from 1.2 to ∼1.0 eV with an increase in the Mg concentration. However, in the low temperature range below 320 °C, there is a continuous decreased from 1.2 eV and then this saturated to ∼0.4 eV with the increase in Mg concentration. The calculated bulk conductivities based on a defect chemistry model explains conductivity for temperatures above 320 °C. The model demonstrates a predominant electronic conduction in the low concentration range below 0.1 mol % Mg and mixed conduction with ionic and electronic carriers in the intermediate and in high acceptor concentration range of 0.2–0.6 mol % Mg. However, the decrease in Eσ with the increase in Mg concentration in the low temperature range could not be explained by the defect chemical model. Such deviation however could be explained by a transition to hopping conduction between ionized acceptor (MgTi″) and neutral or hole-trapped acceptor (MgTi×) with the increase in Mg concentration in the low temperature range.