Influence of misfit stresses on the dielectric permeability of ferroelectric superlattices BaTiO3/BaZrO3

Abstract

Based on the temperature dependences of the dielectric constant and the tangent of the dielectric loss angle in an alternating electric field, the reasons for the increase in the temperature range of the existence of the ferroelectric phase and the increase in the dielectric response of the BaTiO3/BaZrO3 ferroelectric superlattices in comparison with the analogous characteristics of its individual components are discussed. The results of a significant increase in these characteristics for the superlattice under consideration are explained on the basis of the concept of elastic misfit stresses arising in different layers of the superlattice due to the mismatch of the sizes of the unit cells that make up the lattice of single-crystal layers. These stresses lead to the formation of longitudinal polarization in the layers of barium titanate BaTiO3 and to the related contribution of the transverse component of the dielectric tensor to the effective permeability of the superlattice in the direction normal to the plane of the layers. Simultaneously, the misfit stresses of the lattice layers cause the appearance of a ferroelectric phase transition in the barium zirconate BaZrO3 layers in the superlattice with the appearance of spontaneous polarization and an increase in the dielectric constant of this layer in the direction normal to the plane of the lattice layers. The increase in dielectric losses in the low-temperature region is explained by the motion of domain walls in the layers of barium zirconate. Along with the dielectric response, the deformations that arise in the layers of the BaTiO3/BaZrO3 ferroelectric superlattice extend the temperature interval of the existence of the polar state in the lattice layers by several hundred degrees compared to barium titanate.