xPb(In1/2Nb1/2)O-3-(1-x-y)Pb(Mg1/3Nb2/3)O-3-yPbTiO(3) (PIN-PMN-PT) bulks possess excellent electromechanical coupling and dielectric properties, but the corresponding epitaxial PIN-PMN-PT thin films have not yet been explored. This paper adopts a nonlinear thermodynamics analysis to investigate the influences of misfit strains on the phase structures, electromechanical properties, and electrocaloric responses in epitaxial PIN-PMN-PT thin films. The misfit strain-temperature phase diagram was constructed. The results reveal that the PIN-PMN-PT thin films may exist in tetragonal c-, orthorhombic...