The extrinsic contributions to the dielectric response of 0.5Pb (Yb12 Nb12) O3 -0.5 PbTiO3 thin films with (100) or (111) crystallographic orientation were studied (all indices are given in terms of the pseudocubic cell). Both the nonlinearity in the permittivity as well as the polarization hysteresis are described by the Rayleigh Law in subswitching conditions. It was found that (100) oriented films show a slightly higher extrinsic contribution to their dielectric behavior than (111) oriented films. For example, at 1 kHz and oscillation fields of 20 kVcm, for (100) and (111) oriented films, respectively, 25% and 21% of the relative dielectric constant is due to irreversible extrinsic contributions. The difference is attributed to the higher concentration of mobile interfaces in the (100) oriented thin films. For frequencies between 20 Hz and 200 kHz both the Rayleigh parameters dropped with frequency approximately logarithmically. The frequency dependent Rayleigh parameters have been used to modify the Rayleigh Law to allow prediction of the dielectric properties in terms of both oscillation field and frequency.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)