Identifying open-volume defects in doped and undoped perovskite-type LaCoO3, PbTiO3, and BaTiO3

Dopants, vacancies, and impurity-vacancy clusters have a substantial impact on the properties of perovskite-type metal oxides (general formula ABO(3)). In order to determine synthesis and processing conditions that optimize the desirable properties of these materials a careful study of these defects is required. It is essential to identify the defects and to map the defect densities. Positron annihilation spectroscopy has often been used to identify vacancy-type defects. Calculations of the positron lifetime and Doppler-broadened profiles of the positron-electron annihilation radiation in undoped and doped LaCoO3, PbTiO3, and BaTiO3 are reported, and compared with available experimental data. The results show that these positron techniques are excellent for studying open-volume defects, vacancy-impurity complexes, and for identifying the sublattice occupied by the dopants.