The state of dispersion of Pb²⁺ in highly doped KCl crystals

Abstract

The state of dispersion of Pb2+ in highly doped KCl crystals after different heat treatments is investigat,ed. Optical and X-ray diffraction measurements show that the new phase formed in KCl crystals by precipitation of the impurity is imperfectly ordered and composed of agglomerations of cation-vacancy dipoles, different from the case of Pb-doped NaCl crystals where a PbCI, phase is obtained. X-ray diffraction and luminescence data show that after both, strong precipitation and dissolution, the impurity evolves towards the same equilibrium state characterized by partial aggregation of Pba+ cation-vacancy dipoles.On a BtudiB l'btat de dispersion du Pb2+ dans les cristaux de KCI fortement impurifi6s soumis b des diffbrents traitements thermiques. Les mesures de diffraction des rayons X et les donnbes optiques ont conduit b la conclusions que la nouvelle phase obteniie par la prbcipitation du Pb est une phase peu ordonke, formBe par des associations de dipoles Pb2+-vacance, btat different de la phase de PbCI, obtenue dans le cas du cristal de NaC1:Pb. Les rbsultats radiocristallographiques et de luminescence ont indiqub qu'aprks une forte prbcipitation ou aussi bien dissolution, l'impureth bvolue vers un m4me &at d'bquilibre caractkrish par l'agglom6ration partielle des dipoles Pb2+--vacance.

The relationship between local plastic deformation and precipitation morphology in ionic crystals

“…The light-scattering method of Taurel and Girard-Nottin [5] showed that (110)and (100)-rods coexist in KC1:Ca crystals. The same conclusion was arrived a t by Baltog et al [16] for crystals of NaC1:Ba and NaC1:Pb and by Marculescu et al [7] for crystals of KC1:Pb. Furthermore, the results given by Plint and Sibley [18] for KC1:Sr crystals and Abaev and Kornfeld [9] for NaC1:Cd and NaC1:Mn crystals showed that light scattering was only caused by the (100)-rods.…”

On the decay of the luminescence emission of Pb2+ centres in alkali halide crystals

“…However, the shape is nearly exponential, proving that the resonant energy transfer probability 8 is a constant for each sample. The constant probability is an argument in favour of the great dispersion of the lead impurity in the KC1 lattice [13].…”