Complex perovskites: A chessboard at the nanoscale

Nanoscale phase separation into a perfect two-dimensional chessboard structure is observed in a class of perovskite-based lithium-ion conductors. Guiton and Davies have reported the observation of perfect two-dimensional periodic separation, spinodal decomposition, into two compositionally distinct phases. Functionalities can be attained by combining different materials to form composites or heterostructures. Binary nanocomposite superlattices, where size-controlled spherical nanoparticles pack into lattices that replicate the atomic packing seen in the crystal structures of simple binary compounds, represent another elegant example of a periodic composite structure. In general, a spinodal decomposition leads to a mixture of phases that is neither symmetric nor random. This phase separation uses two phases that adopt a periodic ordered superstructure that extends over the entire crystal.