LEAD(II) HALIDES - A NEW CLASS OF ACOUSTOOPTIC AND ELECTRO-OPTIC MATERIALS

A novel and potentially useful class of crystals, the lead (II) halides were recognized by A. V. Zamkov et al. for the acousto-optic and electro-optic and electro-optic devices. Lead bromide, PbBr//2, is the most highly studied of these and was tested for its acousto-optic properties. The crystal possesses certain properties which are highly desirable for signal-processing applications. For this reason, we have developed a method to purify and grow single crystals of this compound. PbBr//2 crystals up to 26 mm in diameter and several cm in length were grown by the Bridgman method. Purification is complicated by oxidation of PbBr//2 in the presence of traces of moisture. Formation of lead chloric left bracket Pb(ClO//2)// 2 right bracket , plattnerite (PbO//2) and mixed oxy halides (Pb//3O//2NBrCl) were observed due to residual chlorine and oxygen impurities. Mendipite was the major constituent of dark bluish residue formed during the purification by directional freezing.