Oxygen vacancy related defects in batio3

Abstract
Depending on the acceptor content of BaTiO3 crystals, two types of Ti3+ ESR signals are observed. Acceptor-poor samples, which thus also have low concentrations of compensating oxygen vacancies, Vo, contain isolated Ti3+ free small polarons. Acceptor-rich crystals show signals to be attributed to Ti3+ next to Vo—alkali-acceptor complexes. This model is supported by a comparison of the optical absorptions and light induced charge transfer transitions of both types of specimens.