The physical origin of the piezoelectric effect has been the focus of much research work. While it is commonly accepted that the origins of piezoelectricity may be intrinsic (related to the change of lattice parameters) and extrinsic (related to the movement of domain walls), their separation is often a challenging experimental task. Here in situ high-resolution synchrotron X-ray diffraction has been combined with a new data analysis technique to characterize the change of the lattice parameters and domain microstructure of a PbZr1−x Ti x O3 (x = 0.45) crystal under an external electric field. It is shown how `effective piezoelectric coefficients' evolve upon the transition from purely `intrinsic' effects to `extrinsic' ones due to domain-wall motion. This technique and corresponding data analysis can be applied to broader classes of materials and provide important insights into the microscopic origin of their physical properties.

LaF3/SrF2 multilayer heterostructures with thicknesses of individual layers in the range 5-100 nm have been grown on MgO(100) substrates using molecular beam epitaxy. The longitudinal conductivity of the films has been measured using impedance spectroscopy in the frequency range 10(-1)-10(6) Hz and a temperature range 300-570 K. The ionic DC conductivities have been determined from Nyquist impedance diagrams and activation energies from the Arrhenius-Frenkel equation. An increase of the DC conductivity has been observed to accompany decreased layer thickness for various thicknesses as small as 25 nm. The greatest conductivity has been shown for a multilayer heterostructure having thicknesses of 25 nm per layer. The structure has a conductivity two orders of magnitude greater than pure LaF3 bulk material. The increasing conductivity can be understood as a redistribution of charge carriers through the interface due to differing chemical potentials of the materials, by strong lattice-constant mismatch, and/or by formation of a solid La1-xSrxF3-x solution at the interface during the growth process.

Synchrotron X-rays on the Swiss Norwegian Beamline and BM28 (XMaS) at the ESRF have been used to record the diffraction response of the PMN-PT relaxor piezoelectric 67% Pb(Mg1/3Nb2/3)O3-33% PbTiO3 as a function of externally applied electric field. A DC field in the range 0-18 kV cm-1 was applied along the [001] pseudo-cubic direction using a specially designed sample cell for in situ single-crystal diffraction experiments. The cell allowed data to be collected on a Pilatus 2M area detector in a large volume of reciprocal space using transmission geometry. The data showed good agreement with a twinned single-phase monoclinic structure model. The results from the area detector were compared with previous Bragg peak mapping using variable electric fields and a single detector where the structural model was ambiguous. The coverage of a significantly larger section of reciprocal space facilitated by the area detector allowed precise phase analysis.

Electrical properties of thin films of La1-xSrxF3-x solid solutions with x = 0 ÷ 0.24 were measured in temperature range from RT to 300°C and wide frequency range from 10−1 to 106 Hz by impedance spectroscopy method. The spectrums of impedance were analyzed with equivalent circuits contain RC and Warburg parts. DC-conductivities were calculated from RC-circuit of impedance and activation energies determined from Arrhenius-Frenkel equation \( \sigma_{DC} T = \sigma_{0} e^{{\left( { - \frac{{E_{\sigma T} }}{kT}} \right)}} \). Diffusion coefficients and their temperature dependencies were determined from Warburg part of impedance for different SrF2 content.

A special cell for single crystal diffraction experiments under applied electric field has been developed and tested. A wide angle scan range provided by the cell allows the data collection in a large volume of the reciprocal space. Test experiments at synchrotron source for ferroelectric and relaxor single crystals show the possibility to the dependence of both Bragg and diffuse scattering on applied electric field. Further development of insitu diffraction methods with the proposed cell at synchrotronbased and laboratory instruments is discussed.

LaF3 films in the 5-40 nm thickness range were grown on Si(111) by molecular beam epitaxy. The substrates were kept at 450 degrees C during deposition. The films were investigated by high-energy X-ray photoemission flanked by conventional X-ray photoemission, reflection high-energy electron diffraction, and atomic force microscopy. The film growth was layer-by-layer. The surface of the films presented flat terraces, similar to 100 nm wide, separated by monatomic steps, reproducing the morphology of the substrate. La 3d, F Is, P Is, and Si 2p core levels and valence band were measured by high-energy photoemission to investigate the reactivity of the system and the surface and bulk composition of the films, following varying sample treatments (X-ray irradiation, sputtering, heating). The fresh prepared films resulted of high purity, with no traces of reaction or intermixing at the buried interface between the substrate and the trifluoride. The X-ray beam was seen to induce F depletion at the surface and promote oxide formation. F depletion enhancement was obtained through Ar ion sputtering. An irreversible variation of the film composition was finally observed for samples heated above 300 degrees C, with the development of La oxides and oxofluorides. These effects were related to the high mobility of F ions in the LaF3 lattice and to the high tendency of defects formation involving F sites.