Effect of Misfit Strain on Pyroelectric Properties of (111) Oriented Pb(Zr_1−xTi_x) O₃ Thin Films

Based on the Landau-Dovenshire theory, the thermodynamic potential of (111) oriented films is constructed to investigate the pyroelectric properties of Pb(Zr_1−xTi_x) O₃ thin films. Due to the presence of nonlinear coupling terms resulted from the (111) epitaxy with substrates, the effects of misfit strain and electric field on the phase transitions at room temperature are more complex than that of (001) and (110) oriented films. Pb(Zr_0.5Ti_0.5) O₃ thin films with the Ti composition around the morphotropic phase boundary (MPB) have the giant dielectric and pyroelectric properties. Moreover, Pb(Zn_1−xTi_x) O₃ thin films grown on the tensile substrates which induce the triclinic γ phase have the larger dielectric and pyroelectric properties than that on the compressive substrates. Therefore, the physical properties of (111) oriented Pb(Zr_1−xTi_x) O₃ thin films can be adjusted by choosing the suitable substrates. (paper)