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Final Activity Report Summary - EHFNA EHMNA (Electron Holography of Magnetic and Ferroelectric Nanoparticles Arrays)

Size effects on the Ferroelectric properties were studied on Nano-particles of BaTiO3 by Electron Holography. Isolated BaTiO3 nano crystals were prepared by a molten hydroxide synthesis. The ferroelectric properties within the nano crystals were characterised using electron holography above and below the Curie temperature, and also by Piezoresponse Force Microscopy (PFM), which can show the piezoelectric properties of the ferroelectric nanocrystals. The results from the electron holography experiments show different behaviour of the polarisation within different BaTiO3 nano crystals with a strong temperature dependence on polarisation. In particular the Curie temperature and the strength of ferroelectric fields were found to be dependent on the size of the nano-particle. This study was the subject of Daniel Szwarcman Thesis, and will be included in his Ph.D. The results were submitted for publication to "Nature Materials". Following the referrers reports and as the issue is on the edge of the field, it was decided that more people in Dresden, including a theoretician will be involved, in order to establish the results. Steps toward this establishment are presently in active and will be examined on a meeting in June 2011.

The 3D of nano wires and nano-tubes was characterised by Electron holography and published. We also apply the off-axis electron holography method to study the 3D morphology of several kinds of soot nano-particles. The soot particles were chosen to demonstrate the capability of incorporation the electron holography method into studies of air pollution. This study was obtained in collaboration with Dr Miroslowa Pawlyta - an expert in characterisation of soot by electron microscopy. The thickness profile of individual soot nano-particles and also network of agglomerated particles are revealed. The results were submitted for publication to "Carbon" Electron holography and atomic resolution study of bulk ferroelectric materials were obtained. The perturbation of reference wave due to charging on sample surface has been solved. Various domain configurations in PZT ceramics have been investigated.

These studies were combined with a Geometric Phase Analysis (GPA) method in order to correlate the results with the local distortion in ferroelectric materials. A perovskite order-disorder ferroelectric material, Pb(Sc1/2Ta1/2)O3, has been studied preliminarily. A new observation is that the ordered and disordered domains induce lattice distortion at their interfaces has been found. In addition to off-axis electron holography, a method of inline holography, Exit-Wave Reconstruction by through-focus series of high-resolution TEM (HRTEM) images, has been establish in Tel Aviv University and included in our studies. The reconstructed complex electron wave function at the exit plane of the specimen can be obtained. An advantage of this technique is the aberration correction. Hence the interpretation of the details in a reconstructed phase image is relatively easier than in the conventional HRTEM image. Defective HfO2 nanorods and Al nano-particles embedded in amorphous Ge matrix are studied and the preliminary results are reported.

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