Piezoresponse force microscopy (PFM) is applied to image ferroelastic formed c domains in a single crystal ferroelectric barium titanate bulk material. A simple model and an analytical approach are presented, which provides a basis to understand the complex tip-surface interactions responsible for the image contrast in PFM. In particular, the measured amplitude of the piezoresponse out-of-plane surface displacements of a C− domain is compared with theoretical results based upon a three-dimensional Green’s function solution. The electric field distribution in the tip-surface contact is determined using image-charge calculations for a spherical tip separated by a thin water layer from a mechanically isotropic and electrically anisotropic dielectric half plane.

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Four-point-bending V-notched specimens of lead zirconate titanate (PZT) poled parallel to the long axis are fractured under conditions of controlled crack growth in a custom-made device. In addition to the mechanical loading electric fields, up to 500V∕mm are applied parallel and anti-parallel to the poling direction, i.e., perpendicular to the crack surface. To determine the different contributions to the total energy release rate, the mechanical and the piezoelectric compliance, as well as the electrical capacitance of the sample, are recorded continuously using small signal modulation/demodulation techniques. This allows for the calculation of the mechanical, the piezoelectric, and the electrical part of the total energy release rate due to linear processes. The sum of these linear contributions during controlled crack growth is attributed to the intrinsic toughness of the material. The nonlinear part of the total energy release rate is mostly associated to domain switching leading to a switching zone around the crack tip. The measured force-displacement curve, together with the modulation technique, enables us to determine this mechanical nonlinear contribution to the overall toughness of PZT. The intrinsic material toughness is only slightly dependent on the applied electric field (10% effect), which can be explained by screening charges or electrical breakdown in the crack interior. The part of the toughness due to inelastic processes increases from negative to positive electric fields by up to 100%. For the corresponding nonlinear electric energy change during crack growth, only a rough estimate is performed.

The breakdown strength as well as the mechanical strength of ceramic materials decreases with increasing volume. The volume-effect of the mechanical strength can be explained by the Weibull theory. For the breakdown strength the same explanation has been often assumed.In order to validate this assumption breakdown strength and mechanical strength of alumina samples with defined porosities were compared. Differences in the Weibull moduli of breakdown and mechanical strength distributions indicate that the volume-effect cannot explain the thickness-dependence of the breakdown strength. In particular, the thicknessdependence of the breakdown strength always leads to a Weibull modulus of two which is not 2 in agreement with the measured Weibull moduli for samples with constant thickness. It can be concluded that the thickness-dependence of the breakdown strength cannot be explained by the Weibull concept. A recently developed breakdown model which is based on space charge injection is able to explain the experimental results.

Ion-beam synthesis of β-FeSi2 is demonstrated both in (111) Si and (001) Si substrates by 450 keV Fe ion implantation at elevated temperatures using a dose of 6×1017 Fe/cm2 and subsequent annealing at 900 °C. The structure of the buried layers has been analyzed using Rutherford backscattering spectrometry, x-ray diffraction, and (cross-section) transmission electron microscopy. In (111) Si an epitaxial layer is formed consisting of grains with lateral dimensions of approximately 5 μm. Epitaxy of β-FeSi2 (110) and/or (101) planes parallel to the (111) Si substrate plane is observed. In (001) Si a layer is formed consisting of grains with lateral dimensions of typically 0.5 μm. Several grain orientations have been observed in this material, among others β-FeSi2 {320}, {103}, and {13,7,0} parallel to (001) Si. Selected (111) Si samples were investigated optically using spectroscopic ellipsometry, and near-infrared transmittance and reflectance spectroscopy. The results confirm that the β-FeSi2 layer has an optical band gap of 0.87 eV. The ellipsometry results indicate that the layers formed by ion-beam synthesis are more dense than those formed by surface growth techniques. Hall measurements show that the β-FeSi2 layers obtained are p type. Mobilities observed are 1–4 cm2/V s at room temperature and approximately 25 cm2/V s at liquid-nitrogen temperature. These results show that the electrical properties of ion-beam-synthesized β-FeSi2 is comparable with those of surface-grown material. The results confirm that optoelectronic applications of β-FeSi2 are limited.