Hello,

it's not that easy. Rietveld's method in combination with the internal standard method is rather used for quantitative estimates of the content of amorphous components. Isomorphic mixing is frequent and difficult to estimate from the Rietveld method. 93-95% agreement of the results when converted to the theoretical composition with the analysis seems very good to me.

Dalibor M.

Dear Saurabh!

1. To quantify amorphous you have to use internal standart. But for complex compositions it usualy yeld an inaccurate result.

2. Since there are usualy some unclearence in phase identification of cements it isn't any necessity in using Rietveld. Corund ratio method in combination with XRF leads to comparable accutacy.

Nikolay Babitskiy Dalibor Matýsek

thanks for the suggestions, I am learning more about refining amorphous phases. I have used direct method (with crystal structure which models peak positions and intensities of amorphous component in cement samples).

As of now i am in interested in crystalline phases but for better fit i have used direct method for few amorphous phases.

The refinement of my data give 93 to 95% of composition with low chi value as shown in the images below.

During refinement the composition was 100% with high chi values but after improved refinement with direct method the difference plot looks much better and the composition changed to 95%.

Can i call this data valid?

thanks

Looking at the composition, I have the impression that you have a overdefined model for Rietveld analysis. Too many similar phases. If I had a raw file, I could look at it in Bruker Topas. Cements are wery complex and require better measurement (longer times per steps for noise reduction).

Dalibor Matýsek

thanks for your opinion, It will be really helpful to get your suggestions on the raw data.

I have attached my raw file (in UXD and ASC format).

My scan rate was 6deg/min and the instrument is Bruker D8advance(Cu).

thanks

saurabh

I send my rather skeptical look. One peak is unevaluated, it is probably some hydrocalumite phase. (Rexp: 5.64, Rwp: 7.09, Rp: 5.50, GOF: 1.26, all in %)

The calculated crystallinity from the peak areas is 72%.

Another note, in Rietveld analysis it is possible to enter only one structurally and chemically close phase. I would recommend a longer measurement time.