Growth conditions influence on thermally stimulated luminescence of sapphire single crystals

The results of investigation of thermally stimulated and photoluminescence as well as absorption spectra of a-sapphire grown by a technique of horizontally directed crystallization in a protective gas medium of varying composition and pressure are presented. This technique has an advantage of minimization of W and Mo erosion, thus providing a considerably reduced prime cost. At the same time, there are some problems connected with emergence of considerable number of anion vacancies, whose in-axis concentration gradient is directed oppositely to that of dopants (mainly Ti). The correlations are found between the conditions of -sapphire growing and the data of absorption and luminescent spectroscopy. An interaction between the anion vacancies and Ti dopants, which induces a transition from electric-charge state Ti⁴+ to Ti³+, is discussed