Monocrystalline red mercuric iodide prepn. - by purification and sublimation of polycrystalline material

摘要

A quadratic monocrystal of mercuric iodide, is prepd. by condensing the vapour obtained from a charge of polycrystalline mercuric iodide, by placing the purified polycrystalline material at one end, (sublimation zone), of a growing ampoule, which has means of germination at the other end, (grown zone); heating the ampoule, to establish a temp. gradient; maintaining a pressure 10-5 - 10-6, and displacing continuously the transfer zone, between the sublimation and growth zones, towards the charge as the monocrystal grows, typically at 1-10 mm/day. The temps. in the ampoule are 80-90 degrees C in the transfer zone. The charge is prepared by direct synthesis from mercury and iodine and purified by one or several zone sublimations followed by one or several zone fusions. The ampoule is cylindrical with one end narrowed to form the growth zone. The ampoule is heated by a mobile electric furnace with three windings. The process gives a larger crystal, volume 10 cm3; than prior art and the crystal is homogeneous and practically free from impurities. The crystals have excellent transparency and crystal perfection, so that they may be used in high precision appts. utilising material of unclear purity.