Studies on the Purification and Single-Crystallization of KI

KI crystals produced in an atmosphere of nitrogen gas by Kyropoulos' method were used as the starting material of crystal productive of zone melting method and Bridgman's method. In the case of the operation of their two methods, the influence of the variation of migration or descent speed was investigated. Concerning thus produced crystals, investigations were performed as to their crystal perfectness and single-crystalli-zations, and further investigations regarding the concentrations of divalent cations, hydroxyl ions and carbonate ions in the crystals. The crystals obtained at the speed of 6 mm/h in both methods showed considerably better single crystallization and perfectness (density of dislocations: 4～6×10^5 cm^-2) than in the case of using other speeds. The meassurements of ionic conductivity were performed within the range of temperatures 100℃～450℃, and activation energy was found to be about 0.36 eV from the curves of logσ-10^3/T°K at about 2.3×10^3/T°K (230℃). Its value was not affected by the concentrations of divalent cations in the crystals. On the other hand, the decrease of the formation energy of vacancy pair was observed when the estimated concentrations of the divalent cations was decreased. Regarding the crystals obtained by zone melting method and Bridgman's method in iodine atmosphere, the characteristic absorption peaks due to the hydroxyl ion and the carbonate ion were not observed in infra-red absorption measurement. Further, it was ascertained by the measurement of ultra-violet absorption at the temperature of liquid nitrogen that the concentrations of the hydroxyl ions in the above mentioned crystals showed a very small value or the extent of a trace.T°K (230℃). Its value was not affected by the concentrations of divalent cations in the crystals. On the other hand, the decrease of the formation energy of vacancy pair was observed when the estimated concentrations of the divalent cations was decreased. Regarding the crystals obtained by zone melting method and Bridgman's method in iodine atmosphere, the characteristic absorption peaks due to the hydroxyl ion and the carbonate ion were not observed in infra-red absorption measurement. Further, it was ascertained by the measurement of ultra-violet absorption at the temperature of liquid nitrogen that the concentrations of the hydroxyl ions in the above mentioned crystals showed a very small value or the extent of a trace