Defect characterization of barium titanates, tantalates and niobates by PAS and ESR

We present first results of a detailed study by both PAS and ESR of the influence of preparation conditions and stoichiometry on the defect chemistry of BaTiO3 and of more complex perovskites with the general formula Ba(B'1/3B''2/3), where B'=Mg,Zn,Ni, and B''=Nb,Ta. In BaTiO3, several paramagnetic defects such as, Ti3+, VBa, and VTi were detected and identified by ESR, and correlated with positron lifetime data. In the more complex perovskites, the positron data are significantly more difficult to interpret and show a strong dependence on the density of the sintered material. (orig.)