Local atomic structure deviation from average structure of Na0.5Bi0.5TiO3: Combined x-ray and neutron total scattering study

摘要: The crystal structure of sodium bismuth titanate (NBT) and related compounds is great interest, as these may form part a new generation ferroelectric materials used in multitude piezoelectric applications. This work examines the short- long-range different states synthesis using x-ray neutron pair distribution function studies. average NBT was modeled monoclinic $Cc$ space group through combined structural refinement diffraction data via Rietveld method. A small box approach to model local based on material, determined from refinement, rule out presence $A$-site ordering NBT. ``box-car fitting'' method analyze showed that bond environments change when averaged over length scales calculated valence Bi${}^{3+}$, particular, locally its value. reverse Monte Carlo allowed positions Na${}^{+}$ Bi${}^{3+}$ move independently, allowing determination their distinctive bonding with O${}^{2\ensuremath{-}}$. revealed have slightly atomic positions, an effect be origin large displacement parameters for $A$ site model. described here discussed comparison published models.