350 nm-thick Perovskite PbZr0.54Ti0.46O3 (PZT) thin films were deposited on Al2O3 substrates by sputtering with and without an additional 10-nm-thick TiOx buffer layer. X-ray diffraction patterns showed that in presence of TiOx buffer layer, PZT film was highly oriented along the (111) direction film, whereas the unbuffered, counterpart was polycrystalline. A full wave electromagnetic analysis using a vector finite element method was performed to determine the tunability and the complex permittivity up to 67 GHz. A comparison between the electromagnetic analysis and Cole-Cole relaxation model was proposed. Through an original study of the relaxation time as a function of the electric field, values, such as 2 ps and 0.6 ps, were estimated for EDC = 0 kV/cm and 235 kV/cm, respectively, and in both cases (111)-PZT and polycrystalline-PZT. The distribution of relaxation times is found to be larger for (111)-PZT film, which is probably related to the film microstructure.