Powder X-ray diffraction

Powder X-ray diffraction technique can be used to characterize the composition and phase of a material.

Powder x-ray diffraction: the powder of a material in order to make sure that all possible crystallographic planes are randomly oriented meaning for a microscopic region all planes are equally probable.

A monochromatic beam of x-ray beam is collimated over the powder sample at an incidence angle $(\theta)$, and the reflected intensity is collected at $(2\theta)$. Once the condition:

$$2d~\sin(\theta) = n\lambda$$

is satisfied, we will have a diffraction peak. Here the $\lambda$ is fixed, we determine the $\theta$, so we can find the $d$, the inter-planner distance. Comparing the set of different inter-planner distances, we can identify the lattice constants.

To make it easier, there are also databases of powder XRD pattern for all known compounds, and we can compare them with the help of a software application.

Resources

• FullProf tutorial on fitting XRD peaks