I have a CeO2-based catalyst.
After adding 1% of Ni, the XRD peak for CeO2 decreases.
But then, when I add 5%, 10%, and 15%, the peak increases. But all the peaks are still lower than the bare CeO2.
The peak intensity is in the following order 0%Ni > 15%Ni > 10%Ni > 5%Ni > 1%Ni.
If we talk about crystallinity, the higher the peak, the higher the crystallinity right? Then, in this case, the CeO2 catalyst decreases in crystallinity when adding 1%Ni, but then the crystallinity improves when adding more metal.
Is this possible? It's not in order.
Dear Abdul Hakim Hatta ,
with respect to the crystallinity you are only partly right: higher peaks may indicate higher crystallinity.
But other parameters also affect the peak height, such as
a) peak broadening (e.g. due lattice strain via Ni in your case, and crystallite size) ,
b) additional x-ray attenuation via adding of Ni, and
c) sample height adjustment, etc.
So what you need is
a) a reference and
b) that reference has to be taken from the XRD pattern itself.
The crystallinity is defined as the ratio of the crystalline informations Icr from the XRD pattern divided by the sum of the crystalline information and the amorphous information Iam.
crystallinity = Icr/(Icr + Iam)
Icr is calcuated from the XRD pattern as the sum of all peak integrals of the crystalline peaks, which are characterized by small peak widths.
Icr +Iam is the integral over the whole XRD pattern including the amorphous background am.
You may have a look at:
https://www.youtube.com/watch?v=D65k1yHPKaM
When doing so, you may have the order of your crystallinity values, which you are expecting...
Good luck and
best regards
G.M.
Dear Abdul Hakim Hatta ,
It is possible for the XRD peak to increase when the amount of Ni is increased. It is likely that, at lower amounts of Ni, there is a higher rate of adsorption of the metal onto the CeO2 surface, which can lead to an amorphization of the lattice and therefore a decrease in peak intensity. At higher concentrations, this may be balanced by an increase in crystallinity due to incorporating more of the metal into the structure and hence an increase in peak intensity.
R. Sagayaraj Thank you very much for your answer. Are there any references that I can read and cite for this information?
To get some feedback, please refer to the latest preprint article at link DOI: 10.13140/RG.2.2.27720.65287/3
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