Paramagnetic defects in BaTiO3 and their role in light-induced charge transport. I. ESR studies

On the basis of a previous identification of paramagnetic defects in nominally undoped as grown BaTiO3 single crystals, we have investigated the changes of the concentrations of these centers and their optical absorptions under illumination with light of varying wavelengths. The most pronounced charge transfers occur by hole ionization of Fe4+ and — to a lesser extent — of Cr5+ and Cr4+. At low temperatures the created holes are trapped in the form of O−-ions next to Al3+ or unknown acceptor defects. Corresponding Fe4+ and O− absorptions have been identified.

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