V3+∶YAG晶体的生长、色心与光谱性能研究

采用石墨电阻加热的温梯法生长了V∶YAG晶体，晶体的不同部位呈现两种不同的颜色：浅绿色和黄褐色.通过对比分析不同颜色V∶YAG晶体的室温吸收光谱，推断出石墨发热体高温下扩散出来的C可以起到还原作用，提高晶体中V³⁺_tetra离子的浓度，同时诱导了F心的形成.在1300℃下，对不同颜色的V∶YAG晶体进行真空退火处理，发现处于八面体格位中的V³⁺离子在热激发作用下与近邻的四面体格位Al³⁺离子存在置换反应，由此产生一定浓度的四面体格位V³⁺离子.同时，F心在退火过程中被完全消除，释放出来的自由电子被高价态的V离子俘获，可以进一步提高晶体中四面体格位V³⁺离子的浓度. 关键词： V∶YAG晶体 四面体格位 碳还原 真空退火 F心

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

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.