Ion-irradiation-induced amorphization ofLa2Zr2O7pyrochlore

Abstract

The isometric pyrochlore structure, ${A}_{2}{B}_{2}{\mathrm{O}}_{7},$ is generally susceptible to radiation damage, but certain compositions are remarkably resistant to radiation damage. In the binary system ${\mathrm{Gd}}_{2}({\mathrm{Ti}}_{2\ensuremath{-}x}{\mathrm{Zr}}_{x}){\mathrm{O}}_{7},$ the radiation resistance increases dramatically with the substitution of Zr for Ti, until the pure end member ${\mathrm{Gd}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ cannot be amorphized, even at doses as high as \ensuremath{\sim}100 dpa. Although zirconate pyrochlores are generally considered to be radiation resistant, we report results for the amorphization of a zirconate pyrochlore ${\mathrm{La}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ by ion beam irradiation (\ensuremath{\sim}5.5 dpa at room temperature). The critical amorphization temperature ${T}_{c}$ is low, \ensuremath{\sim}310 K. The susceptibility to ion-beam-induced amorphization and structural disordering for zirconate pyrochlores is related to the structural deviation from the ideal fluorite structure, as reflected by the x parameter of the ${\mathrm{O}}_{48f}.$