Designing pseudocubic perovskites with enhanced nanoscale polarization

A crystal-chemical framework has been proposed for the design of pseudocubic perovskites with nanoscale ferroelectric order, and its applicability has been demonstrated using a series of represen- tative solid solutions that combined ferroelectric (K 0.5 Bi 0.5 TiO 3 , BaTiO 3 , and PbTiO 3 ) and antifer- roelectric (Nd-substituted BiFeO 3 ) end members. The pseudocubic structures obtained in these systems exhibited distortions that were coherent on a scale ranging from sub-nanometer to tens of nanometers, but, in all cases, the macroscopic distortion remained unresolvable even if using high- resolution X-ray powder diffraction. Different coherence lengths for the local atomic displacements account for the distinctly different dielectric, ferroelectric, and electromechanical properties exhib- ited by the samples. The guidelines identified provide a rationale for chemically tuning the coher- ence length to obtain the desired functional response.