Composition-driven structural variation in ferrielectric phase of (Bi1/2Na1/2)TiO3-Ba (Mg1/3Nb2/3)O3

We investigate the structural variation in the ferrielectric P4bm phase of (1-x)(Bi1/2Na1/2)TiO3-xBa(Mg1/3Nb2/3)O-3 (BNT-BMN) by using high-resolution neutron powder diffraction (NPD) analysis. The NPD study on single-phase BNT-BMN powders obtained by a two-step calcination process reveals that a boundary between rhombohedral R3c and tetragonal P4bm phases exists at x = 4%. The Rietveld analysis reveals that the P4bm phase (x = 5%-10%) exhibits an isotropic expansion of the crystal lattice as well as a decrease in rotation angle of the oxygen octahedra when the BMN composition (x) increases. The compositional-driven variation in the P4bm structure strongly suggests that the polarization and octahedral rotation behaviors associated with phase transition, which is called polarization twist, has a crucial role in the enhancement of polarization properties of BNT-BMN. (C) 2019 The Japan Society of Applied Physics