Quantitative Phase Analysis

 

Quantitative Phase Analysis (sometimes called also Standardless Phase Analysis, Multiphase Rietveld Phase Quantification, Rietveld Quantitative Analysis or Rietveld XRD Quantification) is a powerful method for determining the quantities of crystalline and amorphous components in multiphase mixtures. The method relies on the simple relationship

where W is the relative weight fraction of phase p in a mixture of n phases, and S, Z, M, and V are, respectively, the Rietveld scale factor, the number of formula units per cell, the mass of the formula unit (in atomic mass units) and the unit cell volume (in 3). It is very important to know that commonly used Relative Intensity Ratio (RIR) method is simply not correct and should not be used. Please read our corresponding Technote, where we give proof of inadequacy of RIR method. It should be realized that Rietveld Phase Quantification method for quantification of mixture of 20 phases (with total 6000 reflection) is 30,000 times more powerful than RIR method for quantification of just two phase mixture.

 

Advantages of Rietveld Quantitative Analysis

  • The calibration constants are computed from reliable structural data, rather than by laborious experiments

  • All reflections in the pattern are explicitly included for calculation

  • The effects of preferred orientation and extinction are reduced, since all reflection types are considered

  • Crystal structural and peak profile parameters, particle statistics, microabsorption etc are refined as part of the same analysis.

The phase analysis is performed to determine weight (or volume) quantity of crystalline and amorphous phases which are present in the sample. Standard report of phase identification work includes the following:

  • Sample preparation for diffraction experiment

  • Experimental conditions

  • Diffraction raw data file in original and ASCII formats

  • Figure of the final refined diffraction profile

  • Table with weight percentages of phases present in the sample
     

 

 

EXAMPLE OF STANDARD REPORT

Phase quantification Report

1. Sample Preparation:

One gram of dry sample was hand-pulverized  and 1μm fraction separated with a microsieve  was used for data collection.

 

2. Experimental Conditions:

Part of pulverized sample was top-loaded into the standard glass sample holder (18mm height and 0.8 mm depth), and compacted with a class slide. Data collection was performed using horizontal goniometer Rigaku DMAX-B powder diffractometer with diffracted beam graphite monochromator. Slits DS=1, SS=1, RS=0.15. Two theta angular range=5-80, Step size=0.05, Step time=5 sec.

 

3. Diffraction data file

Diffraction data file in Binary (Z000111.raw), ASCII (A000111.raw) and MS Excel (X,Y) formats are in CD

 

4. Final Rietveld quantification  plot

 

5. Phases Table

The sample consists of the phases given in the Table. No other phases or amorphous components are found to be present in detectable quantities.

 

Phases Weigh,%
Quartz 56.3
Albite 19.3
Anorthite 15.2
Calcite 2.3
Hematite 2.4
Tremolite 2.1
Dolomite 2.4

 

 

 

 

 

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