Habit modification of nearly perfect single crystals of potassium dihydrogen phosphate (KDP) by trivalent manganese ions studied using synchrotron radiation X-ray multiple diffraction in Renninger scanning mode

摘要

The X-ray multiple diffraction technique using synchrotron radiation is applied in the preliminary study of the habit modification of KDP samples as induced by incorporation of the trivalent transition metal cation Mn3+. High-resolution Renninger scans of pure and doped KDP were carried out using 400 as the primary reflection, echoing the fact that these impurity species were segregated in the {100} growth sector. The analysis of the Renninger scans of the doped KDP crystals is consistent with the presence of the impurity species chemically bound within the KDP crystal structure, as confirmed through the suppression of the huge observed peak asymmetry, characteristic of perfect crystals. In addition, an extra Renninger-scan peak measured for the doped material is indicative of the impurity atoms occupying interstitial crystallographic sites in the lattice, a result consistent with X-ray standing-wave measurements. Renninger-scan reflection curve widths and lattice parameter measurements reveal the decrease in crystalline perfection ( increased mosaic spread, eta) and lattice contraction of ca 0.4% in the a and c lattice directions at the surface plane for the Mn3+-doped KDP samples in comparison with the undoped crystals. [References: 37]