Removal of oxidic impurities for the growth of high purity lead iodide single crystals

It could be shown that the hydrogen (H2) treatment of lead iodide (PbI2) is capable to effectively reduce oxidic impurities contained in the source material used for single crystal growth. Comparative experiments of melting PbI2 in H2 and Ar atmosphere as well as thermal analysis (DTA, DSC/TG) of contaminated PbI2 were carried out to characterise the influence of the H2 treatment on the resulting material purity. At the same time, a hygroscopic nature of PbI2 could be disproved, and new results on the controversially discussed thermal behaviour of solid, oxide-polluted PbI2 are presented. Effective measures for the avoidance of oxidic impurities during source material processing could be derived. Finally, the effectiveness of an H2 treatment is confirmed by single crystal growth experiments using the Czochralski technique. PbI2 crystals with improved structural properties and, for the first time, a reproducible predetermination of crystallographic orientation are shown.