Processing of textured ZnO based materials and charaterizaton their anisotropic properties

Non-random distribution of orientations of the grains, which make up the polycrystalline materials, with respect to each other is called texture. This texture makes it possible to have the anisotropic properties of single crystals in the polycrystalline materials. Texture can be obtained by different processes. It is possible to control the material properties by controlling the texture. In this study, highly oriented pure ZnO materials were obtained by utilizing a strong magnetic field (12 Tesla). Microtructure and texture characteristics of the samples were characterized by x-ray and electron diffraction methods. First the process of alignment, under a magnetic field, was optimized. Then the problem of anisotropic sintering shrinkage, which emerges due to high texture, was investigated. By varying the application type of the magnetic field, the texture of the material could be controlled (Like 96 %, 75 %, 27 % and 0 % Lotgering factor). Then, the electrical resistivity (3-0.5 Ohm.cm), hardness (200-150 kgf/mm2), and thermal diffusivities (16.5-18.5 mm2/s) were measured as a function of direction and texture. These measurements showed that the symmetry of the applied magnetic field is transferred to the texture characteristic and thus symmetry of the properties of the polycrystalline material. Finally, polycrystalline ZnO specimens with the highest texture degree and quality were utilized as substrates in growth of ZnO nano-structures. It was observed that the basal and some pyramidal planes, let fabrication of individually grown, aligned nano rods, while the dense films formed on prismatic surfaces.