Disentangling elastic relaxation and ferroelectric domain contributions to in plane X-ray scattering profile: A necessity in strained ferroelectric superlattices

•Ferroelectric nanodomains give rise to satellite peaks in diffuse X-ray scattering.•X-ray diffraction satellite peaks due to nanodomains or elastic relaxation.•Contribution of elastic relaxation evidenced by transmission electron microscopy.•Domain’s electrostatic effect reduces the superlattice Curie temperature.