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

Pb(InNb)O-(1--)Pb(MgNb)O-PbTiO (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 -, orthorhombic -, monoclinic -, and paraelectric PE phases. It is also found that the - and -PE phase boundaries exhibit a superior dielectric constant ε11 which reached 1.979 × 10 with u = -0.494%, as well as the - phase boundary showing a large piezoelectric response which reached 1.64 × 10 pm/V. In comparison, the c-PE and M-aa phase boundaries exhibit a superior dielectric constant ε over 1 × 10 around um = 0.316% and the piezoelectric response 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.