I have 3 different specimens. Each specimen has a main peak of the targeted phase, however, all of them also have a secondary peak of associated with a secondary phase. Now just based on the intensities of the main peak and secondary peak, can I estimate which specimen has the highest amount of secondary phase and which has the lowest?
Someone told me to compare the ratio of peak intensities of secondary phase and the main phase. Is this rough comparison have any significance?
Or do I only look at the intensity value and compare which specimen has the highest numerical value and thus has the highest amount of the secondary phase.
Kindly share any papers which have estimated the amount of secondary phase just by XRD peaks. I am attaching the picture of XRD peaks. (1) is the main phase and (2) is the secondary phase.
Solely based on intensities, thus excluding fitting procedures like the Rietveld refinement, I think that an approach like the texture coefficient or the relative texture coefficient could bring overall useful information about the ratio between the two phases.
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In order to do this, you must surely know that your specimen does not have texture. In a sample with random orientations such as powders, you can in principle catch the trend between these samples based on ratios of intensities. However, you cannot directly use the peak maximums as "Intensity" as your smaller peaks have certain broadening and the two peaks are convoluted. You need to fit a peak function (such as Voigt function) to each peak and then integrate the area under the peaks to obtain Integrated Intensity. Note that the numerical value that you obtain from the ratios DO NOT correspond to phase fractions, they can only be used for comparison with other samples.
You can check chapter related to quantitative phase analysis using direct comparison method in "Elements of X-ray Diffraction" by Cullity for the theory.
Steven Van Petegem Thank you for your insight. Yes, the starting powder is the same for all 3 samples. They were prepared at different temperatures. Expanding on your answer, let's assume that if the major peak intensity value of PTT_150 is greater than PTT_250, and the minor peak intensity value of PTT_250 is greater than PTT_150, is it safe to assume that PTT_150 has a higher amount of major phase and lower amount of secondary phase as compared to PTT_250?
Syed, to your followup question of June 30, I was about to say exactly the same thing as Steven. The reason you want a broader scan range is because that will enable you to confirm or disprove the important assumption of random crystallite orientation.
To demonstrate random - not preferred - orientation you calculate relative peak intensities* of each phase, just comparing intensities for the same phase. Compare those relative intensities to those of a reference pattern.
To compare phase fraction trends, you need to know that the crystallite orientations are random and that the phases have same composition in all the samples. If those conditions are met, then relative peak intensity trends between phases do indicate relative phase fraction trends.
Note that I say "trends" because if all those conditions are met and you observe that
intensity_sample_1_phase_A/intensity_sample_1_phase_B > intensity_sample_2_phase_A/intensity_sample_2_phase_B
then you know fraction of phase A in sample 1 > fraction of phase A in sample 2. But you do not know that fraction of phase A > fraction of phase B in sample 1 just because intensity of phase A > intensity of phase B. You could be comparing a relatively small peak of phase A with a relatively tiny peak of phase B. Also, even if you are comparing each phase's most intense peak, phase B could be a weak scatterer and phase A is a strong scatterer. In both of those cases, you could have a phase B much smaller than the phase A peak, but still lots more of phase B than phase A. To summarize, you need to know
- "I/Ic" of each phase because that value provides a measure of absolute scattering intensity
- the (hkl) of each peak and its relative peak intensity
in order to know more than trends between samples.
forgot to include the * reference
* be sure to always use integrated intensity, not peak intensity.
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