On the width of charged {110} ferroelectric domain walls in potassium niobate

Abstract

High-resolution electron micrographs of {110} domain walls are reported for ferroelectric orthorhombic potassium niobate (KNbO₃). Some of the difficulties of interpreting such images are discussed. It is shown that (1) charged 60° and/or 120° domain walls are present, (2) the domain wall structure is incoherent with a spatial periodicity of approximately 800 Å, (3) there are significant ionic displacements localized within ≤ 15 Å of the walls, (4) there are probably significant changes in electron density over a relatively wider band (∼50 Å) and (5) there are small local departures of domain wall orientation from {110}.