Y : LiNbO3 single crystals with the bulk periodically poled structure were grown by Czochralski technique along [2 (1) over bar (1) over bar 0] (X-axis). The chemical etching pictures of the domain walls and the yttrium concentration curves were superimposed with the help of the marks and WDS analysis traces on the {0 (1) over bar (1) over bar 0} crystal surface (Y-cut). With this novel approach we show that the domain walls are displaced relative to the corresponding impurity concentration minima during the crystal annealing below the Curie point. The new positive domain arises around the electron beam trace on the {0 1 (1) over bar 0} crystal surface.