Dislocation structure at a \[ \{ {\overline{1} 2\overline{1} 0} \}/ {\langle} 10\overline{1} 0 {\rangle} \] low-angle tilt grain boundary in LiNbO3

Abstract

LiNbO₃ is a ferroelectric material with a rhombohedral R3c structure at room temperature. A LiNbO₃ bicrystal with a \[ \{ {\overline{1} 2\overline{1} 0} \}/ {\langle}10\overline{1} 0{\rangle}\] 1° low-angle tilt grain boundary was successfully fabricated by diffusion bonding. The resultant boundary was then investigated using high-resolution TEM. The boundary composed a periodic array of dislocations with \[ b = { 1}/ 3{\langle} \overline{1} 2\overline{1} 0{\rangle} \]. They dissociated into two partial dislocations by climb. A crystallographic consideration suggests that the Burgers vectors of the partial dislocations should be \[ 1/ 3{\langle}01\overline{1} 0{\rangle} \] and \[ 1/ 3{\langle}\overline{1} 100{\rangle} \], and a stacking fault on \[ \{ {\overline{1} 2\overline{1} 0} \} \] is formed between the two partial dislocations. From the separation distance of a partial dislocation pair, a stacking fault energy on \[ \{ {\overline{1} 2\overline{1} 0} \} \] was estimated to be 0.25 J/m² on the basis of isotropic elasticity theory.