Probing point defects inBa(B1/3B''2/3)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'1/3B''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'1/3B''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'1/3B''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'1/3B''2/3)O3 perovskites.