Elastic-plastic and phase transition of zinc oxide single crystal under shock compression

The Hugoniot data for zinc oxide (ZnO) single crystals were measured up to 80 GPa along both the 〈112^¯0〉 (a-axis) and 〈0001〉 (c-axis) directions using a velocity interferometer system for any reflector and inclined-mirror method combined with a powder gun and two-stage light gas gun. The Hugoniot-elastic limits of ZnO were determined to be 10.5 and 11.5 GPa along the a- and c-axes, respectively. The wurtzite (B4) to rocksalt (B1) phase transition pressures along the a- and c-axes are 12.3 and 14.4 GPa, respectively. Shock velocity (U_s) versus particle velocity (U_p) relation of the final phase is given by the following relationship: U_s (km/s) = 2.76 + 1.51U_p (km/s). Based on the Debye-Grüneisen model and Birch-Murnaghan equation of state (EOS), we discuss the EOS of the B1 phase ZnO. The bulk modulus (K₀) and its pressure derivative (K₀′) are estimated to be K₀ = 174 GPa and K₀′ = 3.9, respectively