Origin of ferroelectricity in the lattice dynamics of hafnia

The aim of the project is to investigate the origin of ferroelectricity in the simple binary oxide hafnia HfO2. We propose to measure for the first time the phonon dispersion of ferroelectric hafnia crystals Y:HfO2 by inelastic X-ray scattering complemented by diffuse scattering measurements. The objective is to verify the presence of a nearly dispersionless phonon branch controlling the different phases of hafnia (polar and antipolar). The observation of a flat, strongly temperature phonon band would be key to verify our current understanding of ferroelectricity in this system.