(Pb,Ca)TiO3/(Pb,La)TiO3/(Pb,Ca)TiO3 heterostructure characterized as ferroelectric multifunctional material

Ferroelectric thin films are multifunctional materials with applications in a wide range of microelectronic and microelectromechanical devices. The recent investigations on multilayer heterostructures builtup with ferroelectric layers of different compositions have shown an enhancement of the dielectric, ferroelectric, and pyroelectric properties with respect to the single-component films. In this work, the structural, dielectric, ferroelectric, and pyroelectric properties of a (Pb,Ca)TiO3/(Pb,La)TiO3/(Pb,Ca)TiO3 multilayer heterostructure have been studied and compared with identically prepared (Pb,Ca)TiO3 and (Pb,La)TiO3 films. The heterostructure shows a higher dielectric permittivity in the whole temperature interval up to the transition temperature, and a higher tetragonal distortion with respect to the single-component films, revealing a lower residual stress in the heterostructure. Optimized ferroelectric and pyroelectric properties have been achieved in the heterostructure, with maximum values of remanent polarization, Pr, and pyroelectric coefficient, γ, of Pr=27 μC cm-2 and γ=51x10-9 C cm-2 K-1. A mechanism of stress relaxation by plastic deformation through vacancies diffusion is proposed to explain the enhanced properties