Misfit-Strain Phase Diagram, Electromechanical and Electrocaloric Responses in Epitaxial PIN–PMN–PT Thin Films

xPb(In(1/2)Nb(1/2))O(3)-(1−x−y)Pb(Mg(1/3)Nb(2/3))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 aa-, monoclinic M-, and paraelectric PE phases. It is also found that the c-M and aa-PE phase boundaries exhibit a superior dielectric constant [Formula: see text] which reached 1.979 × 10(6) with u(m) = −0.494%, as well as the c-M phase boundary showing a large piezoelectric response d(15) which reached 1.64 × 10(5) pm/V. In comparison, the c-PE and M-aa phase boundaries exhibit a superior dielectric constant ε(33) over 1 × 10(5) around um = 0.316% and the piezoelectric response d(33) reached 7235 pm/V. The large electrocaloric responses appear near the paraelectric- ferroelectric phase boundary. These insights offer a guidance for experiments in epitaxial PIN–PMN–PT thin films.