Mechanical properties of irradiated Gd_2Zr_2O_7 pyrochlores as studied by nanoindentation technique - Effect of grains and grain boundaries

摘要

The influence of ion irradiation on nanomechanical properties of Gd_2Zr_2O_7 pyrochlore have been studied. The polycrystalline samples were irradiated at room temperature with 320 keV Ar ions with fluences from 2 × 10~(14) to 1 × 10~(16) ions/cm~2. Nanomechanical properties of grains and grains boundaries were measured by means of nanoindentation technique. The measurements were performed in the centers of the grains and at the grain boundaries and point to the conclusion that grain boundary region is usually characterized by higher hardness and Young's modulus than the center of the grain. The analysis performed suggests that the stress induced effect related to the transition to anion-deficient fluorite structure leads to the increase of recorded hardness values and may be considered as primary source of hardening. Studied phenomenon depends on the irradiation fluence and may serve as an indicator of the structure modification in the irradiated sample. Finally, nanomechanical properties of irradiated grain boundaries were interpreted in the frames of incorporation of foreign species near grain boundary.