On twinning of lithium niobate crystals under uniaxial loading

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Abstract
Lithium niobate single crystals were subjected to uniaxial mechanical loading along their rhombohedral axis [111] in the mode of constant deformation rate (from 5 to 50 μm/min) in the temperature interval from 20 to 850°C. It is shown that beginning from the temperature 300°C the deformation of tested samples is realized mainly by formation of structural twins. Temperature dependence of the twinning processes at lower temperatures (T < 650°C) was found to have an activational character. X-ray analysis has shown that creation of the mechanical twins may be considered in this case as a process of mutual structural domain transfer of the rhombohedral phase, whose axes orientations are coupled through the virtual cubic (parent) cell.