Interplay of Local Polarization, Ionic Size, and Octahedral Tilt in SrTiO3-Na0.5Bi0.5TiO3

We show that the ferroelectric system (1- x)SrTiO3-(x)Na0.5Bi0.5TiO3 exhibits an interesting interplay of local polarization, ionic size effect, and octahedral tilt. This interplay results in (i) a nonmonotonic composition dependence of the lattice volume at room temperature and (ii) existence of a unique temperature (300 degrees C) at which the competing effects of electrostriction caused by the formation of polar nanoregions and geometrical ionic size make the system exhibit composition independent lattice parameters in a large composition interval x < 0.40.