Direct mapping of microscopic polarization in ferroelectricx(BiScO3)−(1−x)(PbTiO3)throughout its morphotropic phase boundary

Abstract

Pair distribution functions of ferroelectric $x{\mathrm{BiScO}}_{3}\text{\ensuremath{-}}(1\ensuremath{-}x){\mathrm{PbTiO}}_{3}$, obtained from neutron total scattering data, were examined and modeled utilizing the reverse Monte Carlo technique to depict exclusively the local structure of this compound throughout its reported morphotropic phase boundary (MPB). Microscopic polarizations due to the cation shifts have been mapped out from the refined crystal structure as a function of composition in order to reveal individual cation behavior driven by the composition. Direct evidences are provided for large static displacements of the cations $(\ensuremath{\sim}0.2\ensuremath{-}0.5\phantom{\rule{0.28em}{0ex}}\AA{})$, local cation ordering between Ti and Sc, and a categorical change of favored polarization directions of the cations at the conjuncture of the MPB. Apart from Sc, all cations have demonstrated an apparent transition from a relatively defined directional distribution to a broad and random distribution at $x={x}_{\mathrm{MPB}}$, suggesting a flattening of the local potential function for them. These features can further be correlated with the general concept of structural instability of a ferroelectric system at the MPB, which is often linked to the manifestation of enhanced physical properties.