Yielding and phase transition under shock compression of yttria-doped cubic zirconia single crystal and polycrystal

Abstract

Inclined-mirror Hugoniot measurements of yttria (Y2O3) -doped (9.6 and 8.0 mol %) cubic zirconia single crystal and polycrystal were performed in the pressure range up to 120 GPa to study yielding and phase transition. The Hugoniot-elastic limit (HEL) stresses parallel to the 〈100〉 and 〈110〉 axes were approximately 14 and 25 GPa, respectively, while that of the polycrystal was approximately 13 GPa. Above the HELs the Hugoniot data parallel toward the 〈100〉 and 〈110〉 axes converged on each other, and showed large relief to an isotropic compression state, while those of the polycrystal preserved a considerably larger shear strength. A phase transformation took place at approximately 53 GPa (both 〈100〉 and 〈110〉 axis directions), and was completed by about 70 GPa. The phase transition pressure was much higher than those of the monoclinic- or tetragonal-orthorhombic II phase transitions under static compression. The shock velocity Us versus particle velocity Up relation of the final phase of the single crystal was given by Us=2.19+2.35Up km/s. The equation of state of the final phase was analyzed by using a program based on the Debye model, the Mie–Grüneisen equation, and the Birch–Murnaghan equation. The volume change between the cubic phase and the final phase at zero pressure was estimated to be 20%, which was larger than that expected for the cubic-orthorhombic II transition. The bulk moduli of the final phase at zero pressure were estimated to be 510 GPa.