Determination of the Transition Pressures of Some Alkali Halides under Hydrostatic Pressure with X-Ray Diffraction Method
Although many reports have been presented concerning the polymorphic transition pressures of alkali halides, there have been few reliable studies with respect to the hysteresis phenomena. Recently Lacam and Peyronneau  observed the definite hysteresis loops of several rubidium halides Controlling such conditions as purity of the specimen, heat treatment, and pressurization rates. For the potassium halides, on the other hand, which have higher transition pressures  than those of rubidium halides, no reliable hysteresis loop was reported. Mizouchi  measured the transition pressures of potassium chloride as a test of his new pressure apparatus both in compression and decompression runs, but his result is unlikely to be regarded as a hysteresis loop. In order to explain the hysteresis phenomena, therefore, the lattice constants of the potassium halides were measured using the x-ray diffraction technique at pressures including the phase transition. The specimens studied were KCl, KI, KBr, and KF.
KeywordsHysteresis Loop Hydrostatic Pressure Diffraction Line Sample Chamber Transition Pressure
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