  We investigate the microstructural evolution in a ferroelectric to
antiferroelectric phase transition at the morphotropic phase boundary in the
Bi(1-x)SmxFeO3 system. Continuous Sm3+ substitution on the A-site induces
short-range anti-parallel cation displacements as verified by the appearance of
localized 1/4(110) weak spots in selected area electron diffraction patterns
for 0.1<x<0.14 samples, and thus onset of antiferroelectricity. Kinetic Monte
Carlo simulations confirm that increasing the strength of the anti-parallel
interactions (i.e. increasing x) induces a ferroelectric to antiferroelectric
transition. For 0.14<x<0.2 antiphase oxygen octahedra tilts induce complete
antiferroelectricity.
