Evaluation of intrinsic and extrinsic contributions to the piezoelectric properties of Pb(Zr1−XTX)O3 thin films as a function of composition

Abstract

The piezoelectric, dielectric, and ferroelectric properties of highly (111)-textured, 200-nm-thick polycrystalline lead zirconate titanate (PZT) films have been investigated as a function of Zr/Ti ratio. The distinct peak in piezoelectric coefficient at the morphotropic phase boundary found in bulk PZT ceramics is not observed in thin film PZTs. Measurements of the temperature dependence of relative permittivity and the nonlinear behavior of relative permittivity and piezoelectric coefficient suggest that non-180° domain wall motion in these films is negligible, indicating that the extrinsic contribution to the room temperature permittivity is dominated by only 180° domain wall motion. The semiempirical phenomenological equation relating the piezoelectric coefficient to measured polarization and permittivity values is demonstrated to give an excellent description of the piezoelectric behavior in these films, assuming bulk electrostrictive and elastic coefficients. The small deviation between calculated and measured piezoelectric coefficients as well as the dependence of piezoelectric and polarization behavior on the external field, i.e., hysteresis loop, are suggested to be primarily due to backswitching of 180° domains.