Complex dielectric behaviour during formation of BaTiO3 by combustion synthesis

Abstract

Complex dielectric behaviour was observed during the combustion synthesis of polycrystalline barium titanate in the presence of a 0.1–100 kHz ac electrical field. The ac conductivity (σ) and relative dielectric permittivity (ε) attained their maximum values during the initial stage of the combustion at ∼850 °C before the temperature reached its maximum (∼1340 °C) and before complete conversion of the reactants to the product BaTiO3. The duration of the ac conductivity and relative dielectric permittivity at 0.1 kHz were much shorter (∼90 ms) than at 100 kHz (∼3 s). The low frequency response is probably dominated by massive charge carriers (O2−, Ti4+ Ba2+), while that at high frequency by light charge carriers (electrons, holes). The temporal ac conductivity, relative dielectric permittivity and temperature suggest that most charge carriers were generated when the reaction rate was maximal.