Ferroelastic Behavior in Relaxor 24Pb(In_(1/2)Nb_(1/2))O_3-46Pb(Mg_(1/3)Nb_(2/3))O_3- 30PbTiO_3 under Shear Stresses along [001] Direction

摘要

The ferroelastic behavior of relaxor 24Pb(In_(1/2)Nb_(1/2))O_3-46Pb(Mg_(1/3)Nb_(2/3))O_3-30PbTiO_3 (PIN-PMN-PT) solidsolution single crystals was investigated under shear stresses using polarization light microscopy (PLM) and the scanning electron microscopy (SEM). Optical strain patterns along the {110}cub directions from the orthoscope images under crossed Nicol, induced by shear stresses applied along the (001)cub direction, making use of a Vickers microindenter with a square-base diagonal line oriented along the f100gcub directions of the crystal were observed on its {001} cub plate for the first time. These patterns at a diagonal position reveal a flowerlike pattern for ferroelastic transition from a square (S) lattice to a rectangular (R) lattice in a two-dimensional model system. A change in the interference color from yellow to blue through red toward the center in their flower leaves, according to the Michel- Levy birefringence chart, was observed. The patterns at the extinction position reveal starlike patterns coupled with lobes also due to orthorhombic and/or tetragonal twin domain structures. A blue shift (corresponding to addition in retardation) and a yellow shift (corresponding to subtraction in retardation) in color at each flower leaf in the {110}_(cub) and [110]_(cub) directions were respectively observed using a sensitive color plate. Such shifts in color correspond to oxygen octahedra being rotated in a staggered sense about the perovskite axis. The patterns appearing strongly along the {110}_(cub) directions in spite of slip lines along the [100]_(cub), [010]_(cub), and [110]_(cub) directions indicate the existence of a rotational preferred orientation in twin domain structures based on a pretransitional tweed domain structure due to platelets observed by SEM, leading to their superior piezoelectric properties due to large shear modes.