Crystallographic texture
Qualitative analysis can be done by Laue photography, simple X-ray diffraction or with a polarized microscope.
For drawn metal wires the cylindrical fiber axis turned out as the sample direction around which preferred orientation is typically observed (see below).
The full 3D representation of crystallographic texture is given by the orientation distribution function (ODF) which can be achieved through evaluation of a set of pole figures or diffraction patterns.
The making of metal sheet often involves compression in one direction and, in efficient rolling operations, tension in another, which can orient crystallites in both axes by a process known as grain flow.
However, cold work destroys much of the crystalline order, and the new crystallites that arise with annealing usually have a different texture.
Texture in ceramics usually arises because the crystallites in a slurry have shapes that depend on crystalline orientation, often needle- or plate-shaped.
Casting or other fluid-to-solid transitions (i.e., thin-film deposition) produce textured solids when there is enough time and activation energy for atoms to find places in existing crystals, rather than condensing as an amorphous solid or starting new crystals of random orientation.
Material properties such as strength,[6] chemical reactivity,[7] stress corrosion cracking resistance,[8] weldability,[9] deformation behavior,[6][7] resistance to radiation damage,[10][11] and magnetic susceptibility[12] can be highly dependent on the material’s texture and related changes in microstructure.
[6][7] As the result of substrate effects producing preferred crystallite orientations, pronounced textures tend to occur in thin films.
[13] Modern technological devices to a large extent rely on polycrystalline thin films with thicknesses in the nanometer and micrometer ranges.
In the case of oxide compounds intended for transparent conducting films or surface acoustic wave (SAW) devices, for instance, the polar axis should be aligned along the substrate normal.
[14] Another example is given by cables from high-temperature superconductors that are being developed as oxide multilayer systems deposited on metallic ribbons.
[15] The adjustment of the biaxial texture in YBa2Cu3O7−δ layers turned out as the decisive prerequisite for achieving sufficiently large critical currents.
The determination of texture gradients by x-ray scattering, however, is not straightforward, because different depths of a specimen contribute to the signal.
