The Rietveld-internal standard method for Bragg-Brentano reflection geometry (q/2q) X-ray
diffraction (XRD) patterns is implemented to determine the amorphous phase content. The effect
of some minor phases on quantitative accuracy is assessed. The numerical simulation analysis of
errors and the related corrections are discussed. The results reveal that high purity of crystalline
phases in the standard must be strictly ensured. The minor amorphous or non-quantified crystalline
phases exert significant effect on the quantitative accuracy, even with less than 2 wt% if ignored.
The error levels are evaluated by numerical simulation analysis and the corresponding error-accepted
zone is suggested. To eliminate such error, a corrected equation is proposed. When the adding
standard happens to be present in sample, it should be also carefully dealt with even in low amounts.
Based on that ignorance, the absolute and relative error equations (DAE, DRE) are derived, as proposed.
The conditions for high quantitative accuracy of original equation is strictly satisfied with a lower
amount of standard phase present in sample, less than 2 wt%, and a higher dosage of internal standard,
larger than 20 wt%. The corrected equation to eliminate such quantitative error is suggested.
