Phase transition and EOS of zinc sulfide (ZnS) under shock and static compressions up to 135 GPa

Shock and static compression experiments were performed on zinc sulfide (Zn S) polycrystal in the pressure range up to 135 GPa to investigate the phase transition and equation of state (EOS). Hugoniot data were measured by mea ns of the inclined-mirror method combined with a powder gun and two-stage l ight gas guns, and the static X-ray diffraction experiment was conducted us ing a diamond-anvil cell. This material behaved as an elasto-isotropic soli d which lost its shear strength above the Hugoniot-elastic limit (less than 4.4 GPa). The phase transition from zinc blende-type (B3) to rock salt-typ e (B1) took place at approximately 15.7 GPa under shock compression, and fi nished up to about 37 GPa. The corrected phase transition pressure at 298 K was 15.5 GPa. It was confirmed by the static X-ray diffraction experiment that the B1-type phase was stable at the pressure range up to 80 GPa. The u nstable inclined-mirror images over 75 GPa, double inclined-mirror images o ver 99 GPa, and a discontinuous decrease in free-surface velocity between 8 7 and 99 GPa were observed. The melting and decomposition were discussed in relation to these peculiar free-surface motion behaviors. The density, Gru neisen parameter, bulk moduli (K-0) and the pressure derivative (K-0') of t he B1-type phase were estimated to be 4.91 +/- 0.03 g/cm(3), 0.96 +/- 0.03, 105 +/- 6 GPa and K-0' = 3.8 +/- 0.1 (K-0" = - 0.05 GPa(-1)), respectively . (C) 1999 Elsevier Science Ltd. All rights reserved.