Defect Studies in BaTiO_3 Ceramics Using Positron Annihilation Spectroscopy

摘要

Temperature-dependent measurements using positron lifetime Spectroscopy (POLIS) were carried out to study intrinsic defects in polycrystalline BaTiO_3 (BT) samples. Annealing under different oxygen partial pressure of < 10~(-15) to 10~5 Pa were carried out. It was found that with decreasing oxygen pressure the average lifetime increases. This is attributed to the formation of complexes containing oxygen vacancies V_o and other vacancies, probably V_(Ba). The influence of the grain boundaries on the trapping probability in ceramic BT material was studied. It was found that the average positron lifetime increases distinctly with decreasing grain size.