Induced ferrielectricity in chlorapatite

Abstract

Application of an external electric field of 1300 V/mm ∥ c induced the displacement of ∼3% of the chloride ions in the channels of a chlorapatite crystal with composition Ca10−x (PO₄)₆Cl2−2x □2x (x = 0.03). The percentage of the displaced ions corresponds to the concentration of the vacancies in the channels. The displacements bring about a partial reversal of the elementary dipoles in the ideally antiferroelectric structure and thus lead to a ferrielectric phase. At a field strength of 5000 V/mm chlorapatite became optically uniaxial and possibly ferroelectric.