X-Ray dilatometric study of the phase transition of the improper ferroelectrics KH₂PO₄and KD₂PO₄

Abstract

Abstract X-ray dilatometric measurements were made on lattice strains of KH2PO4 and KD2PO4 as a function of temperature and biasing electric field near the Curie point. The electrostriction contained in the lattice strains x1, x2 along the a-and b-axes cannot be explained in terms of the ordinary electrostrictive effect. In order to interpret these new effects, the phenomenological theory of improper ferroelectrics has been successfully applied. The difference of the transition mechanism between KH2PO4 and KD2PO4 is discussed from the same viewpoint of improper ferroelectrics.