Quantitative Compound Analysis
General XRD - Quantitative Compound Analysis
AMIA Laboratories specializes in the investigation and characterization of materials using the latest advances in x-ray diffraction. We can help you determie if or which x-ray analysis will help in your materials characterization. The quantification of an XRD pattern can produce percentages of crystallographic phases. Quantitative Analysis (Semi-Quant and Reitveld) are the two major quantification for crystallographic phases. Percent crystallinity, latice parameters and crystallite size are other quanitative measurments of a crystallographic phase.
General XRD: Semi-Quant Analysis
General XRD: Rietveld Analysis
More Rietveld Analysis
Rietveld Analysis may be considered a Fundamental Parameters program for XRD. It refines various parameters including lattice parameters, peak width and shape, and preferred orientation to derive a new diffraction pattern. Once the derived pattern is nearly identical to the original data, various properties pertaining to the sample can be obtained including:
- Accurate Quantitative Results (usually to within ±1%)
- Crystallite Size
- Site Occupancy Factors
There are many methods for conventional quantitative analysis. Most need standards to achieve reasonable accuracy. The standardless or RIR method is usually accurate to within ±3%. For better accuracy a standards method is used. There is a considerable time investment involved in preparing and measuring standards. It is an accurate technique, but inflexible. If a new component enters the method, additional standards must be prepared.
Rietveld Analysis doesn't use standards. Instead, it calculates how the diffraction profiles are affected by the different crystal properties previously mentioned. It continues to refine its estimates of the new diffraction profiles and computes a difference pattern. As this difference becomes smaller, the derived pattern begins to look more like the original data. At some point there is no improvement, and the refined pattern's parameters are used to calculate results. The process of refining the pattern is compute-intensive, but with the advent of modern powerful PC's it takes approximately 20 minutes to calculate results for a 12-component mixture, a task nearly impossible using conventional methods.
The main advantage of Rietveld Analysis over conventional quantitative methods is that no standards are required to achieve accurate results to within ±1%.
