Orientational order parameters in the lead ytterbium tantalate phase transition

Abstract

We have found two orientational order parameters and their major roles in the phase transition of lead ytterbium tantalate (PYT). The zenithal order parameter was found to be associated with the phase transition from paraelectric to antiferroelectric phase and thus the magnitude of the dielectric constant. The azimuthal order parameter plays a main role in the diffuse phase transition between the antiferroelectric and the unknown phase. Our hard-mode spectroscopic analysis shows the unknown phase cannot be ferroelectric but antiferroelectric.