STUDIES OF THE IMPURITY EFFECTS ON CRYSTALLINE QUALITY BY HIGH-RESOLUTION X-RAY DIFFRACTION

Abstract

Sr(NO3)2 single crystals with different impurities doped were grown from aqueous solutions. The distribution of impurities in Sr(NO3)2 crystals were investigated by electron probe micoranalysis. Results show that the distribution of impurities illustrates a compositional zoning behaviour. The Ba2+ has a higher concentration in the {100} growth sectors than in the {111} sectors. On the contrary, Pb2+ has a higher concentration in {111} growth sectors than in {100} sectors. The crystalline perfection of the pure and Ba2+ or Pb2+ doped Sr(NO3)2 crystals was studied by high-resolution X-ray rocking curve technique. The high-resolution X-ray rocking curve of the ideal Sr(NO3)2 crystal was theoretically calculated based on the dynamical X-ray diffraction theory. High-resolution X-ray diffraction results show that the crystalline quality in the growth sectors of the pure Sr(NO3)2 crystal is fairly high, since its experimental rocking curve is very close to the theoretical calculation. However, in the areas of the sector boundary the full width at half maximum of the rocking curve gets broader due to the lattice stress in the boundary area. The doping of impurities will deteriorate the quality of the crystal and induce an inhomogeneity behaviour of the crystalline quality. As for the Ba2+ doped Sr(NO3)2 crystal, the crystalline quality in {111} growth sectors is higher than that in {100} sectors. On the contrary, the crystalline quality in {100} growth sectors is higher than that in {111} sectors for Pb2+ doped Sr(NO3)2 crystal. This coincides well with the composition distributions of the dopants.