The monoclinic structural distortion in lead phosphate and lead arsenate is correlated with the ferroelastic phase transition R3̄m → C2/c and R3̄m → P21/c respectively. The resulting domain patterns in the mixed compounds depend on their chemical composition. The intersection of ferroelastic W domain walls with the (100) surface of lead phosphate-arsenate mixed crystals has been imaged using tapping mode atomic force microscopy. Dilution of the strain leads to characteristic surface deformations which deviate from those in pure lead phosphate. In high twinned lead phosphate-arsenate, X-ray diffraction (XRD) was used to show renormalization effects and scattering phenomena stemming from the twin walls. The wall trajectory was found to be independent of chemical variations using transmission electron microscopy.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Imaging soft matter by transmission electron microscopy (TEM) is anything but straightforward. Recently, interest has grown in developing alternative imaging modes that generate contrast without additional staining. Here, we present a dark-field TEM technique based on the use of an annular objective aperture. Our experiments demonstrate an increase in both contrast and signal-to-noise ratio in comparison to conventional bright-field TEM. The proposed technique is easy to implement and offers an alternative imaging mode to investigate soft matter.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007

Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005

Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005

The thermal stability of amorphous Zr:Al mixed oxide films of different composition, produced on (001) silicon wafers by the atomic layer deposition method is studied by transmission electron microscopy during in situ heating experiments. The temperatures at which phase separation and crystallization occur are composition dependent. The crystallization of thick films (55–70 nm), deposited on HF-treated silicon surfaces covered with a 15 cycles Al2O3 layer, results in the formation of cubic ZrO2 and cubic γ–Al2O3. In very thin films (5 nm), deposited on silicon surfaces covered with a 0.5 nm SiO2 thin film, the formation of tetragonal zirconium disilicide (ZrSi2) is observed in the microscope vacuum, at temperatures above 900 °C. This effect depends on the thickness of the as deposited thin film.

The microstructure of BaTiO3 thin films, epitaxially deposited on (001) MgO by pulsed laser ablation, has been investigated by transmission electron microscopy. The films are always c-axis-orientated, but dislocations, {111} stacking faults, and antiphase boundaries are frequently observed. Conventional TEM and high-resolution microscopy allow one to deduce the Burgers vectors of dislocations as b1 = 〈100〉 or b2 = 〈110〉, both being perfect dislocations. Most extrinsic stacking faults are ending at 1/3〈112〉 or 1/3〈111〉 partial dislocations; the displacement vector of the antiphase boundaries is 1/2〈101〉. Studying the interfacial structure by means of zone images taken along [100] and [110] shows that the misfit is mainly released by dislocations with Burgers vectors of 1/2〈110〉 and 1/2〈101〉.

The microstructure of NdNiO3 thin films deposited on Si (100) has been investigated by high resolution electron microscopy. Deposition at 250 °C and 600 °C and several annealing at high temperature under oxygen pressure were performed. Depending on the deposition temperature and annealing conditions, different texture and microstructure were observed. Relationships between microstructure and transport properties are discussed. The differences of grain boundaries are suggested to be responsible for the difference in transport properties of the films.

Positron lifetime spectroscopy is an effective tool to study various types of defects in materials including nanostructured ones. The size of free volumes associated with defects can be estimated using the lifetime components found in the measured spectra. Positron lifetime experiments are performed on nanocrystalline Ni-Al samples synthesized by the inert-gas condensation technique. The samples are further characterized by means of X-ray diffraction, electron diffraction and microscopy techniques as well as density measurements. In the lifetime spectra we observe three lifetime components corresponding to different annihilation sites in the samples. These lifetimes are compared with the results of simulations of positron lifetimes in modeled Ni-Al samples obtained using molecular dynamics and Monte Carlo calculations. Finally, we present positron lifetime results for nanocrystalline Ni3Al samples which were produced or annealed at different temperatures.

Different structural configurations of nanoparticles have been investigated by advanced transmission electron microscopy (TEM) techniques. The cluster-surface interaction of Au clusters, produced in a laser vaporization source and deposited with low energy on MgO cubes, is investigated by high-resolution transmission electron microscopy (HRTEM). A dilation of the Au lattice that perfectly accommodates the misfit with the MgO lattice is measured and modeled with Molecular Dynamics (MD). To study the chemical ordering in bimetallic clusters, Au-Cu alloy clusters with different stoichiometries are produced and deposited in the same way as the Au clusters. Electron diffraction (ED) ring patterns obtained from these alloy clusters lying on amorphous carbon, are indexed as face-centered cubic, which is confirmed by HRTEM. This indicates that clusters of Au-Cu alloys are solid solutions, i.e. no ordering takes place in these clusters. Assembled nanoclusters of Ni3Al, produced by the inert gas condensation (IGC) technique and pressed under high pressure (2 GPa), are investigated by HRTEM. These studies indicate that nanocrystalline Ni3Al consists of small crystallites of random crystallographic orientations separated by grain boundaries, with the presence of several nanoscaled voids. From the selected area electron diffraction (SAED) ring pattern, an incomplete L12 ordering is concluded.

Nanocrystalline titanium dioxide was prepared via aerosol pyrolysis of titanium alkoxide precursor at 200–580 °C in air and in nitrogen atmospheres. Powders were characterized by x-ray diffraction, thermogravimetric analysis, Brunauer–Emmett–Teller analysis, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, x-ray fluorescence, Raman and infrared spectroscopy, and Berner-type low-pressure impactor. The anatase phase transition was initiated at 500 °C in nitrogen and at 580 °C in air. Under other conditions amorphous powders were observed and transformed to nanocrystalline TiO2 via thermal postannealing. In air, smooth and spherical particles with 2–4-μm diameter were formed with an as-expected tendency to convert to rutile in the thermal postannealings. In nitrogen, a fraction of the titanium tetrabutoxide precursor evaporated and formed ultrafine particles via the gas-to-particle conversion. At 500 °C thermally stable anatase phase was formed in nitrogen. A specific surface area as high as 280 m2 g−1 was observed for an as-prepared powder.

The PbO–Nb2O5 phase diagram has been investigated, using electron diffractionand high resolution electron microscopy (HREM), for [Pb]/[Nb] ratios between 1 and1.25. Apart from the basic pyrochlore structure, different long periodsuperstructures, forming a homologous series Pb2n+1Nb2n−1O7n−1 based onthe pyrochlore structure have been found. Members with n = 5, 7, 9, 11 have beenobserved and their structure determined based on electron diffraction and HREM. Imagesimulations allow studying the influence of cation and oxygen vacancies in the basicstructure. Ordering of oxygen vacancies could be detected while no cation vacanciesare observed. Deviations from the perfect structure and ordered stacking defects arediscussed.

Phase transitions are often accompanied by pre-transition effects. These effects have been studied on an atomic scale by high resolution electron microscopy. For the diffusion controled phase transitions we discuss short range ordering effects in Ni-Mo and Cu-Pd. For the displacive transitions we discuss the martensitic nucleation in Ni-Al and the nanoscale domain formation in the Ni-Ti R phase.

NdBaCuO superconductors have been textured by the oxygen controlled melt growth method. The addition of platinum or Nd422 does not refine the 422 phase, but the latter improves the microstructural quality. High purity precursors are necessary to achieve high Tc and Jc (up to 56 000 A/cm2). The flux pinning mechanisms are discussed in terms of oxygen deficiency, Nd-Ba substitution and softening of the vortex lattice.