Piezoelectric Properties of Pb_1-xLa_x(Zr_0.52Ti_0.48)_1-x/4O₃ Thin Films Studied by In Situ X-ray Diffraction

The piezoelectric properties of lanthanum-modified lead zirconate titanate Pb_1-xLa_x(Zr_0.52Ti_0.48)_1-x/4O₃ thin films, with x = 0, 3 and 12 mol% La, were studied by in situ synchrotron X-ray diffraction under direct (DC) and alternating (AC) electric fields, with AC frequencies covering more than four orders of magnitude. The Bragg reflections for thin films with low lanthanum concentration exhibit a double-peak structure, indicating two contributions, whereas thin films with 12% La possess a well-defined Bragg peak with a single component. In addition, built-in electric fields are revealed for low La concentrations, while they are absent for thin films with 12% of La. For static and low frequency AC electric fields, all lanthanum-modified lead zirconate titanate thin films exhibit butterfly loops, whereas linear piezoelectric behavior is found for AC frequencies larger than 1 Hz.