Crystal growth, color centers and spectra properties of V3+∶YAG grown by TGT

Abstract

A V∶YAG single crystal was grown by the temperature gradient technique (TGT) with graphite heating elements, which exhibited two kinds of colorations of light-green and yellow-brown in different parts. Differences in absorption spectra of three samples with different colors suggest that the reduction effect of carbon diffused from the heating element should enhance the concentration of tetrahedral V3+ ions and induce the F color centers with absorption band peaking at 370nm. The three samples all exhibited light-green color after annealing under vacuum at 1300℃. From changes of their absorption spectra, it can be inferred that tetrahedral V3+ ions should be produced through the exchange of octahedral V3+ and tetrahedral Al3+ ions in neighboring sites under heat exciting. During the process of annealing, the F color centers were thoroughly eliminated and the escaped free electrons could be captured by V ions with higher valance states than +3 to further improve the concentration of tetrahedral V3+ ions.