High purity lead iodide for crystal growth and its characterization

Article abstract of DOI:10.1016/0025-5408(92)90141-L

High-purity lead iodide (PbI₂) is prepared by precipitation of lead nitrate (Pb(NO₃)) and potassium iodide (KI) solutions. Thoroughly dried PbI₂ is then zone-refined. The main impurity causing strong adherence of the solidified melt to the glass ampoule wall is identified as lead hydroxyl iodate (Pb(OH)I). In order to decrease the OH^- concentration and consequently the deviation from stoichiometry, molten PbI₂ is treated with a gaseous mixture of methylene iodide (CH₂I₂) and iodoethane (C₂H₅I). The criterion for the efficiency of this scavenging process is the removal of the adhesive effect; thus, the solidified PbI₂ ingot can move freely in the ampoule. A wet chemical analytic method for determining the deviations from stoichiometry is described.