I'm using TOPAS for quantitative analysis by Rietveld refinement. In many cases, amorphous is present in my samples. What will be the consequences if the density of the amorphous phase differs largely while other crystalline phases are same?
This can affect the results of quantitative analysis. Crystals 2023, 13(10), 1485; https://doi.org/10.3390/cryst13101485 partially explains this.
My suggestion is to add the amorphous phase, defined as a broad peak, to the refinement process in TOPAS. Do not forget to define the composition of this phase. This can bring the result of the quantitative analysis closer to the true result.
Do you consider the presence of amorphous phase during the refinement? If not all the phases percentages are wrong. You can prepare a sample by mixing your phases with a known amount of a crystalline phase (such as alumina), then collect the powder pattern. In Topas this known phase is defined as spiked phase and on this basis the program can correct the percentages of the other crystalline phases, that otherwise will be wrong.
Marcella Bini thanks for your reply. Yes, I use a known amount of crystalline phase as an internal standard to quantify phases including amorphous phase. But, my question is, if the density of the amorphous phase differs largely in different samples (assuming all other crystalline phases are same), what will be the consequences in quantitative phase analysis by Rietveld?
I apologize for taking the floor again on this issue. I want to help you and I'm also interested in your final result.
Burhanuddin Burhanuddin :"if the density of the amorphous phase differs largely in different samples (assuming all other crystalline phases are same), what will be the consequences in quantitative phase analysis by Rietveld?"
I think the answer to this question is given in Figures 5 and A7, with function plots for different values of the A parameter in Crystals 2023, 13(10), 1485; https://doi.org/10.3390/cryst13101485 . As you can see the resulting intensities (Intensity changes) depend mainly on the absorption mass and the packing factor. As a consequence, the texture is also affected by the different shapes of grains of different phases. See also section 3.2.
My idea is that you should do an experiment for known amounts and check the results with the Rietveld method.
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