POLYTYPISM OF VAPOR-GROWN PBI2 CRYSTALS

Pure single crystals of lead iodide have been grown from vapor and characterised by X-ray diffraction for their polytypism and related phenomena. The theoretical estimation of the Jackson's alpha-factor and the surface micrographs of the crystals, coupled with the results of X-ray diffraction, indicate crystal growth by two-dimensional nucleation. Comparison of the experimental results with the earlier ones on gel-grown and melt-grown crystals reveals an obvious influence of the impurities on polytype formation, besides confirming the high purity of the vapor-grown crystals.