Non-stoichiometry and its implications for the properties of PMN-PT thin films

0.67[Pb(Mg1/3Nb2/3)O-3]-0.33[PbTiO3] (PMN-33PT) epitaxial thin films were prepared by pulsed-laser deposition (PLD) using ceramic targets, enriched with PbO (and MgO). The phase composition and crystal structure were analyzed by high-resolution X-ray diffraction. Accurate chemical analysis of the thin films was carried out using wavelength-dispersive X-ray spectroscopy, which revealed that the target-substrate material transfer is not fully stoichiometric. The largest deviations were found for Pb and Mg content. Our results show that it is possible to effectively tune the stoichiometry of the films via the use of custom-made ceramic targets, emphasizing their advantage over single-crystal targets in PLD growth of complex metal oxides. The functional response of the films, however, is the result of complex interactions between the crystal structure, microstructure and chemical composition of the films. Our results show that the sample, prepared from the target with 20 mol% PbO excess, with the largest deviations from the nominal stoichiometry, exhibits the highest longitudinal piezoelectric coefficient.