Combined Analysis

Chapter 6

Quantitative Phase Analysis

6.1. Standardized experiments

There are many ways of calculating the phase amounts from diffraction patterns [KLU 74]. All the methods rely on the comparison of a given peak intensity, groups of peak intensities, or even whole-pattern analysis, with those of a standard sample. However, for such methods the problem is shifted to the creation of the reference standard. In many cases the standard can provide sufficiently accurate determinations of the weight and volume fractions; however, quantitativity can be lost if other factors, e.g. texture, amorphous phase, porosity, absorption, etc., are present and uncontrolled. The necessity of calibration through standards represents a major drawback, which, however, can be avoided, as will be seen in the following.

6.2. Polycrystalline samples

Quantitative phase analysis can be performed without the need of a standard on multi-phase samples using the formalism described by Hill and Howard [HIL 87b], if the phases are all crystallized. Looking at equation [2.4], we can rewrite:

[6.1] 

Here m_Φ is the mass of phase Φ present in the sample and m_cΦ is the mass of one unit cell of phase Φ. The weight fraction W_Φ of the phase Φ can then be written as:

[6.2]

where Z_Φ is the number of formula units per unit ...