Characterizing Structure, Defects, and Chemistry

Abstract

In this chapter we will discuss techniques that can produce useful information about the structure, chemistry, and bonding in ceramics. There are so many characterization methods available that books are written on each one. Since we cannot cover all the details or even all the techniques, we will give examples and aim at making you aware of the key ones and their applications.

We can group the techniques into six categories:

• Imaging using visible (or nearly visible) light

• Imaging using electrons [mainly scanning electron microscopy (SEM) and transmission electron microscopy (TEM)]

• Imaging using sensing [atomic force microscopy (AFM) and other scanned probes that “sense” a force or field]

• Scattering and diffraction (using X-rays, neutrons, α-particles, electrons)

• Spectroscopy and spectrometry [using X-rays for energy dispersive spectrometry (EDS) and wavelength dispersive spectroscopy (WDS), Raman, infrared (IR), etc.]

• Thermal analysis (measuring changes, e.g., enthalpy, as a function of temperature)

Most of the techniques we describe can be used to study other classes of materials, but our examples will all be related to ceramics.

The suitability of a characterization technique depends on the type of information we hope to obtain and may also be dictated by the size of our sample, what part of the sample is important, and whether we can destroy the sample. There are some limitations:

• Reflection techniques examine only surfaces.

• Techniques using electrons require the sample to be in a vacuum.

• Techniques using transmitted electrons generally require the sample to be thin.

• For nanomaterials we need high resolution.

We always ask two questions:

• How much material is required for the analysis?

• Is it destructive or nondestructive?

For example, TEM is invariably destructive, but you need a very small amount of material for the analysis.