THE PURIFICATION AND PREPARATION OF HIGH-PURITY PBCL2 AND TERNARY ALKALI LEAD CHLORIDE SINGLE-CRYSTALS

Purification and crystal growth of PbCl2 and congruently melting terna ry alkali lead chlorides, KPb2Cl5, RbPbCl3, RbPb2Cl5, and CsPbCl3, wil l be described in the present paper. Source materials were purified by the chlorination of molten chlorides with gaseous mixture of chlorina ting agents in combination with a subsequent zone-melting. The efficie ncy of this method is confirmed by chemical analysis before and after purification and by the behaviour of the melts. Large single crystals of PbCl2, KPb2Cl5, RbPb2Cl5 and CsPbCl3, 20 mm in diameter and 50-60 m m long, were grown by the Bridgman method. Their quality was checked b y the optical absorption and elastic light scattering measurements.