IMPROVED TECHNIQUE FOR HGI2 PURIFICATION

The modified procedure used in our laboratory to purify commercially a vailable mercuric iodide consists of a sequence of steps: (1) distilla tion under continuous evacuation, followed by (2) repeated sublimation in a closed tube, and (3) recrystallization in the presence of free i odine. Our objective for the iodine treatment in the recrystallization purification is to improve the stoichiometry which was interfering wi th the crystal perfection. Detector and spectrometer quality crystals (up to 340 g) have been grown using our purified raw materials by the modified vapour phase located point method (VPLPM). The stoichiometry of HgI2 was determined by energy dispersive X-ray spectroscopy (EDX) a nd differential thermal analysis (DTA). The perfection and nuclear spe ctroscopic performance of the grown crystal are also studied.