The effect of misfit strain on the phase diagram and pyroelectric effect in (110) oriented Pb(Zr1−xTix)O3 thin films

The phase diagram and pyroelectric effect of (110) oriented Pb(Zr1−xTix)O3 thin films with different Ti composition are investigated by a phenomenological Landau-Dovenshire theory. The tetragonal (a1) phase, the orthorhombic (a2c) phase, and the triclinic (γ) phase are stable. The compressive misfit strain favors the orthorhombic (a2c) phase, whereas the tensile misfit strain makes the triclinic (γ) phase and the tetragonal (a1) phase stable. At room temperature, the misfit strain induces the first order phase transition from the orthorhombic a2c phase to the triclinic γ phase in the Pb(Zr1−xTix)O3 (x=0.4, 0.5, 0.6) thin films. Moreover, even in the γ phase of Pb(Zr1−xTix)O3 (x=0.4, 0.5) thin films, the first order γ1-γ2 phase transition may happen with increasing the tensile misfit strain. The Pb(Zr0.5Ti0.5)O3 thin film with the Ti composition around the morphotropic phase boundary has the largest dielectric and pyroelectric properties, which is in agreement with the experimental result. A critical electric field exists and results in the non-monotonic variation of dielectric and pyroelectric properties with the misfit strain in Pb(Zr0.5Ti0.5)O3 thin film. The positive pyroelectric coefficient is obtained in the γ2 phase of Pb(Zr1−xTix)O3 (x=0.4, 0.5, 0.6) thin films.