The dehydration of potassium alum induced by shock loading

Shock-induced dehydration and structural change on potassium alum, KAl(SO$_{4}$)$_{2}$ $\cdot$ 12H$_{2}$O, has been studied up to a peak pressure of 8 GPa. The shock-recovered samples have been characterized using Raman spectroscopy, x-ray diffraction (XRD), and a scanning electron microscopy (SEM). Although the sample shocked at 5 GPa are consolidated and recovered, no evidence for structural change or dehydration is obtained. However, prominent change of texture and color of the recovered sample shocked at 8 GPa is observed. The XRD results reveal that the recovered sample shocked at 8 GPa consists of anhydrous potassium alum crystals with amorphous. This structure differs from that of dehydrated alum caused by heat. The critical pressure for the shock-induced phase transition is close to the transition pressure from alum crystal to amorphous phase, which is obtained by static pressure loading.