Micropillar compression of LiF [111] single crystals: effect of size, ion irradiation and misorientation

Abstract

The mechanical response under compression of LiF single crystal micropillars oriented in
the [111] direction was studied. Micropillars of different diameter (in the range 1–5 lm)
were obtained by etching the matrix in directionally-solidified NaCl–LiF and KCl–LiF eutectic
compounds. Selected micropillars were exposed to high-energy Ga+ ions to ascertain the
effect of ion irradiation on the mechanical response. Ion irradiation led to an increase of
approximately 30% in the yield strength and the maximum compressive strength but no
effect of the micropillar diameter on flow stress was found in either the as-grown or the
ion irradiated pillars. The dominant deformation micromechanisms were analyzed by
means of crystal plasticity finite element simulations of the compression test, which
explained the strong effect of micropillar misorientation on the mechanical response.
Finally, the lack of size effect on the flow stress was discussed to the light of previous studies
in LiF and other materials which show high lattice resistance to dislocation motion.