X-ray Spectroscopy Study on the Local Structures of Ferroelectrics

X-ray absorption spectroscopy (XAS) is an element-specific technique that provides information on the electronic states and local coordination environments around selected ionic species. The element selectivity of XAS is particularly valuable in the study of ferroelectrics, where ionic coordination structures directly influence the ferroelectric polarization. This article explains the principles behind the element selectivity of XAS and presents several case studies demonstrating how the technique can distinguish between various structural phases such as those arising from overall changes in crystal structure or shifts in the ratio of coexisting phases near a morphotropic phase boundary. Additionally, we introduce the study of ferroelectric ionic displacements at specific locations using polarization-dependent scanning transmission X-ray microscopy.