Light-induced coloration and transformation process in YAlO3 crystal

The nature of point defects in YAlO3 (YAP) which brings great influence on the crystal properties has not been fully established. The UV-irradiated crystal exhibits broad additional absorption bands in the range of 200–800 nm while the additional absorption bands 200–800 nm can be reduced, with a re-irradiation of a 457 nm green laser. The light-induced coloration and transformation mechanism is studied and it is found that the increase or decrease of both UV and visible absorption bands are related to the creation and annihilation of anion vacancies (VO2+ and F+) and cation vacancies (VAl3− and VY3−). It is proposed that the creation and annihilation of VO2+, F+, VAl3− and VY3− may be caused by the separation and recombination of the vacancy clusters [VO2+–VAl3−–F+] and [VO2+–VY3−–F+], which play important roles in the formation and transformation process of light-induced color centers in YAP crystal.