Light-induced charge transport processes in photorefractive Ba0.77Ca0.23TiO3 doped with iron

Photorefractive barium-calcium titanate crystals with the congruently melting composition (Ba0.77Ca0.23TiO3) doped with iron are annealed in a hydrogen atmosphere at various temperatures. The samples are studied with electron paramagnetic resonance (EPR) and optical absorption, both performed separately as well as simultaneously, before and after illumination. The reduced samples are electron conductive and the charge transport at room temperature is governed by only one level identified by photo-EPR as Fe2+/3+. The optical absorption of Fe2+ is found to be peaked at 1.9 eV.