Phenomenological thermodynamic potentials for bulk and thin-film Ba(Zr0.08Ti0.92)O3 single crystals

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Phenomenological thermodynamic analysis is an important theoretical investigation method for ferroelectric materials, however, it cannot be implemented for Ba(ZrxTi1−x)O3 due to the lack of thermodynamic potential coefficients. In this paper, we have constructed a phenomenological thermodynamic potential for bulk Ba(Zr0.08Ti0.92)O3 single crystals, which reproduces the three phase transition temperatures, dielectric and piezoelectric constants of bulk Ba(Zr0.08Ti0.92)O3 single crystals well, suggesting that the constructed thermodynamic potential is reliable. Then the thermodynamic potential with appropriate modification is applied to predict misfit strain-temperature phase diagram and electromechanical properties of Ba(Zr0.08Ti0.92)O3 thin films. It is found that compressive strain favors the tetragonal c phase with an out-of-plane polarization component, while tensile misfit strain favors orthorhombic aa phase with an in-plane polarization component. It also reveals that Ba(Zr0.08Ti0.92)O3 thin films under appropriate compressive strain show higher piezoelectric coefficient d15 than that of their bulk counterpart. The constructed thermodynamic potential opens a new avenue to theoretical analysis on Ba(Zr0.08Ti0.92)O3.