Identifying open-volume defects in doped and undoped perovskite-typeLaCoO3,PbTiO3

Dopants, vacancies, and impurity-vacancy clusters have a substantial impact on the properties of perovskite-type metal oxides (general formula $\mathrm{AB}{\mathrm{O}}_{3}).$ 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 ${\mathrm{LaCoO}}_{3},$ ${\mathrm{PbTiO}}_{3},$ and ${\mathrm{BaTiO}}_{3}$ 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.