Abstract
The spatial distribution of UV-blue absorbing point defects in Bridgman grown bismuth germanate (Bi 4(GeO 4) 3) crystals has been imaged by means of UV absorption topography. From the occurence and position of growth bands and sector boundaries it was concluded that in all conditions the crystals only grow via the crystallographic non-equivalent {112} and {ovbar|112} facets. The exclusiveness and the F-type character of the (slower growing) {112} and (faster growing) {ovbar|112} faces were confirmed by sphere growth experiments and ex-situ surface microtopography. Within many crystals it was found that the {112} sectors show a higher UV-blue absorption and thus an enhanced impurity segregation than the adjacent {ovbar|112} sectors. This point to kinetically (i.e. non-equilibrium) determined segregation. Imaging of crystals by the Schlieren method showed a higher optical density for the {ovbar|112} growth sectors. Laser light scattering disclosed a preferential occurence of inclusions near sector boundaries.
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