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

It could be shown that the hydrogen (H sub(2)) treatment of lead iodide (PbI sub(2)) is capable to effectively reduce oxidic impurities contained in the source material used for single crystal growth. Comparative experiments of melting PbI sub(2) in H sub(2) and Ar atmosphere as well as thermal analysis (DTA, DSC/TG) of contaminated PbI sub(2) were carried out to characterise the influence of the H sub(2) treatment on the resulting material purity. At the same time, a hygroscopic nature of PbI sub(2) could be disproved, and new results on the controversially discussed thermal behaviour of solid, oxide-polluted PbI sub(2) are presented. Effective measures for the avoidance of oxidic impurities during source material processing could be derived. Finally, the effectiveness of an H sub(2) treatment is confirmed by single crystal growth experiments using the Czochralski technique. PbI sub(2) crystals with improved structural properties and, for the first time, a reproducible predetermination of crystallographic orientation are shown.