Crystallization kinetics of amorphous lead zirconate titanate thin films in a microwave magnetic field

We investigated the crystallization process and kinetics of lead zirconate titanate (PZT) thin films fabricated in the magnetic field of microwave irradiation. The PZT thin films were prepared by the sol gel method and crystallized by microwave irradiation at 2.45 GHz. X-ray diffraction was used to identify the phases and to determine the volume fraction of the perovskite phase transformed during crystallization. Transmission electron microscopy gave information on nucleation, growth and grain structure. We also discussed how the crystallization and phase transformations correlated to the ferroelectric properties of the resultant films. We found that an intermediate phase formed during initial crystallization; it had a perovskite-like crystal structure, but it had a smaller lattice constant than perovskite PZT and contained more Ti. This intermediate phase acted as a nucleation site for the perovskite PZT, which grew with a columnar grain structure into the pyrochlore matrix throughout the film. Using Avrami's model, we found the effective activation energy for crystallization of the PZT films by microwave irradiation to be similar to 214 kJ mol(-1), lower than the activation energy for crystallization by conventional thermal processes. These results show that microwave irradiation indeed affected the crystallization of amorphous PZT thin films differently than conventional annealing. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.