Probing point defects in Ba()O3 by ESR, PAS and dielectric spectroscopy

In contrast to simple ternary perovskites (e.g., SrTiO3 and BaTiO3), the defect chemistry model of complex barium perovskites with general formula Ba( B 1 / 3 ′ B 2 / 3 ″ )O3 has yet to be developed. In an attempt to gain an insight into a point defect chemistry of these compounds, we present first results of electron spin resonance, positron annihilation spectroscopy and dielectric spectroscopy (10–100 GHz) of Ba( B 1 / 3 ′ B 2 / 3 ″ )O3, where B′ = Mg, Zn, Ni, Co and B″ = Nb and Ta. Both extrinsic and intrinsic defects were found in these materials. A Mn ion impurity serves as an excellent sensor for the early stages of the B-site cation disorder and oxygen activity. Based on the several Ba( B 1 / 3 ′ B 2 / 3 ″ )O3 examples, we demonstrate that Schottky disorder plays a crucial role in the high temperature phase stability and dielectric loss of Ba( B 1 / 3 ′ B 2 / 3 ″ )O3 perovskites.