Domain wall contributions to properties in PZT

In lead zirconate titanate, the mobility of domain walls governs the stability of the domain state as a function of temperature, drive field, and time. A novel approach to quantitatively deconstruct the relative permittivity into three contributions (intrinsic, reversible extrinsic and irreversible extrinsic) was developed using a combination of X-ray diffraction and Rayleigh analysis. For tetragonal {001} textured Pb_0.99(Zr_0.3Ti_0.7)_0.98Nb_0.02O₃ thin films clamped to a Si substrate, a thickness-dependent in-plane tensile stress developed during processing which dictates the domain distribution. However, after the films were partially declamped from the substrate and annealed, the residual stress was alleviated. The volume fraction of c-domains was used to calculate the intrinsic relative permittivity. The reversible Rayleigh coefficient was used to separate the intrinsic and reversible extrinsic contributions. The reversible extrinsic response accounted for ~50% of the relative permittivity and was thickness dependent even after poling and release.

A second factor that is critical to domain wall motion is microstructural features. Using piezoresponse force microscopy, it was found that triple points typically serve as deep pinning sites, for which domain wall motion can be degraded with a radial width of influence of up to 527 ± 38 nm. Moreover, at the triple points, the nonlinear piezoelectric response is often non-Rayleigh-like in character, suggesting that the domain walls locally see a non-Gaussian set of restoring forces. It was found that different grain boundaries influenced the mobility of domain walls on length scales from 124 ± 23 nm to 575 ± 73 nm normal to their respective grain boundary. The largest width of influence recorded up to 905 ± 153nm. The minimum values of the irreversible/reversible Rayleigh constants, α/d_33,init, were found to be larger for Coincident Site Lattice boundaries compared to random grain boundaries.