Dependence of dielectric and piezoelectric properties on film thickness for highly {100}-oriented lead magnesium niobate-lead titanate (70/30) thin films

Fiber textured {100}-oriented lead magnesium niobate-lead titanate (PMN-PT) (70/30) films with thicknesses between 0.35 and 2.1 mum were prepared usin g chemical solution processing. The degree of preferred orientation changed little with increasing thickness. However, the measured dielectric constan t, remanent polarization, and piezoelectric coefficients (d(31)) increased with increasing film thickness. The effective d(31) coefficients of highly (100)-oriented PMN-PT films on Pt-coated Si substrates were found to range from -16 to -96 pC/N. Ultraviolet illumination during poling resulted in ab normal aging behaviors and lower overall aging rates for the films. The ini tial nonlinear aging behavior was attributed to the presence of an internal space-charge field that developed from photoinduced charge carriers. As th e space-charge field decays over time, the magnitude of d(31) increased unt il 450-500 min after poling, at which time d(31) remained either constant o r declined slightly. Thus, the changes in d(31) were Limited to 1-2%/decade 500-600 min after poling.