Dear Saurabh Khandelwal ,

as mentioned, is it is a paste, the possible diffraction peaks are going to be much attenuated by the significant amount of water.

it would be possible to use portlandite amount determined by TGA to have an approximate phase concentration, hardly comparable to other associated phases in the X-ray. However, all crystalline phase are going to have their intensity affected by matrix self absorption of the X-ray beam.

Higher the amount of water, lower the detectable amount of crystalline phases, the higher the width of each of the phases in the X-ray, when detectable. The effect is also severe on amorphous part of your sample. Basically it would be a severe superposition of very large peaks. you may still see only highly crystalline phases such as quartz, silicates, and so on. Even crystalline, lower phase amounts will be completely hidden in the overall matrix diffraction, if any.

I guess it would be almost impossible to reach a physically meaningful convergence result under a paste-like sample, whatever the used internal standard.

Best regards

WNM

I completely agree with Dr. Wagner Da Nova Mussel

In general, for an arbitrary case, the process of determining phase conformation is to start with an approximate value and finding the best fit by refinement.

But, here for paste sample, it will be extremely difficult. Rietveld refinement works good for high quality crystalline samples generally.

In the same subject:

Regarding Reitveld's improvements or (Reitveld refinements ), it is difficult to apply them to the samples in form of thin films for several considerations, which we include below:

1- Hugo Rietveld described a technique for the characterization of crystalline materials called Rietveld refinement. Powder sample diffraction with neutrons and X-rays produces a pattern with reflections (intensity peaks) at certain locations. Many features of the crystalline material's structure can be determined by measuring the height, width, and position of these reflections. The Rietveld technique refines a theoretical line curve using a least-squares approach until it fits the measured curve. As a result, this process is utilized to analyze powder samples for the crystalline materials in order to cope with significantly overlapping reflections.

2- In summary, Rietveld evaluation is a method that uses the d-value to filter and determine the lattice parameters, allowing the real intensity of a phase or plane to be theoretically computed. This method yields very precise values for d, lattice parameters (a, b, and c), and another parameter. Thus, according to this method, the analyzed powder sample's strain, crystallinity, estimated Intensity, statistical analysis ( W% of elements, phases), and so on may all be computed. It's challenging with thin-film samples.

Thanks, Dr. Wagner Da Nova Mussel

I didn't know about this aspect in the refinement. Your suggestions are very helpful.

I have one additional doubt, In my samples, I have used hydrated polished cement disk for XRD and used this data for Rietveld to compare portlandite content in different samples (without any internal standard), as you mentioned the water significantly interfere with the crystalline phases, can I use my data for comparative study in different samples?

Dear Saurabh Khandelwal ,

as far your sample and reference has the same physical properties and preparation, it has still been possible to be used with parsimony.

Physical meaning would only be achieved when standard or reference, follows the real sample physical-chemical properties and preparation.

Only under those conditions, both are submitted to the same interferences and instrumental response.

Best regards,

WNM