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Further improvement of the power conversion efficiencies of conventional perovskite ferroelectric oxides has been strongly impeded by their wide band gaps. Here, we use several band gap engineering strategies to design low band gap ferroelectric materials from first principles. We show that polarization rotation is useful for reducing the band gaps of strongly distorted perovskites. A variety of visible-light ferroelectric solid solutions are designed by combining Zn substitution into KNbO3with polarization rotation. Alternatively, the band gaps can be reduced by the introduction of low-lying intermediate bands through Bi5+substitution. With this strategy, two Bi5+-containing visible-light ferroelectric solid solutions are designed, which exhibit comparable bulk photocurrent to that of prototypical ferroelectric oxides, but with lower photon energies, as evidenced by the shift current calculations. [ABSTRACT FROM PUBLISHER]

Relaxor ferroelectrics have been a focus of intense attention due to their fascinating physical properties. Their diffuse phase transitions have been explained by the polar nanoregion model. Nevertheless, fundamental characterization of structure and dynamics in relaxors is still a long-standing challenge. Better scientific understanding of the microscopic origins of relaxor behavior is also required to improve efficiencies of relaxor based devices. Our molecular dynamics studies in 0.75PbMg1/3Nb2/3O3-0.25PbTiO3showed good agreement with experimental data and revealed conflicts with the current polar nanoregion model. Here, we review our work and propose an alternate model for structure and dynamics in the relaxor phase. [ABSTRACT FROM PUBLISHER]