OPTICAL AND PHOTOELECTRICAL STUDIES OF CHARGE-TRANSFER PROCESSES IN YALO3-TI CRYSTALS

The donor and acceptor charge-transfer transitions in YAlO3:Ti3+/Ti4were investigated through absorption, emission, excitation, one-photon and two-photon photoconductivities, excited-state absorption, and the rmoluminescence. The results are contrasted to similar studies previou sly made on Al2O3:Ti3+/Ti4+. The dominant Ti3+ population has a photoi onization threshold at 37 000 cm(-1). The lowest energy Ti4+ charge tr ansfer transition has its zero-phonon energy near to 33 900 cm(-1). Th e sum of these two quantities agrees with the reported band-gap energy of YAlO3. The position of the Ti3+/Ti4+ level in the band gap of YAlO 3 is determined by these measurements. Stimulated emission from the (2 )E State of Ti3+ is limited by photoionization from this state.