Texture (orientation) Analysis
How are the grains or crystallites oriented with respect to a sample surface or direction?
Texture, also called orientation, measures the preferred orientation of crystallites in a sample. Usually this technique is used on manufactured materials such as polymers, ceramics, semiconductors and metals. Natural produces can also have orientations as a result of growth conditions, stress or pressure. Examples of natural materials are silk, minerals and cotton fibers. The texture of a material determines physical properties of materials, such as strength and conductivity.
Texture (orientation) analysis can be performed by collecting data pertinent to the sample texture (see Method table). If a full description of all orientations are necessary, a set of complete pole figures are collected and used to determine an ODF (Orientation Distribution Function).
For samples with simple fiber texture, a limited set of data is sufficient to quantify the texture strength via fiber texture plots, which are slices of a pole figure. Ratio methods (integrated line intensities from coupled q:2q scans) are also used for relative comparisons of texture direction and strength, but do not indicate a % random (percent of un-oriented crystallites). Also, these limited approaches do not measure texture correctly if the pole intensity is slightly off-axis or tilted from the perfect normal direction to the sample surface.
Although texture results can be difficult to interpret, display software, which shows results in pole figure space and the reporting of volume fractions and a random fraction makes it easier to relate the crystallite orientation to the sample's surface. Most important is the use of a two dimensional detector which covers a large section of multiple Debye rings, making texture measurements easier and more reliable than conventional ratio methods or rocking curves.
An X-ray Diffraction Service Laboratory