Abstract
Powder X-ray diffraction is widely used as an analytical method to evaluate various crystalline materials. This paper describes the basics and evaluation examples of the RIR (Reference Intensity Ratio) method and the Rietveld method.
In the RIR method, quantitative analysis is performed based on the integrated intensity of diffraction peaks and the RIR values registered in databases. In this method, rapid quantitative analysis is performed once qualitative analysis has been completed. However, if the peak intensity ratio differs from that in the database due to preferred orientation or other reasons, the obtained quantitative values will be inaccurate.
The Rietveld method is a method for refining crystal structure parameters by fitting a calculated pattern obtained from lattice parameters, crystal system, atomic coordinates, etc., to a measured diffraction pattern using the least-squares method. The obtained scale factor and information about the crystal structure can be used for quantitative analysis. The Rietveld method enables accurate quantitative analysis even if samples have preferred orientation and/or complex diffraction patterns.
The combination of the Rietveld method with the internal standard method, known as the PONKCS (partial or no known crystal structure) method, and the RIR method also enable quantitative analysis of amorphous phases.