I worked with Fe3O4 for quite a long and had gone through this problem in 2018. For iron oxides, synthetic conditions are extremely important. Let me explain why.

Iron oxide and oxyhydroxides have almost 20 different polymorphs, out of which, at least 7 are stable in ambient conditions. During the synthesis procedure, if you accidentally oxidize the system, you'll get gamma-Fe2O3, also known as maghemite. This phase also converts to hematite on open-air heating. If you have a look on the reaction-mechanisms, you'll find, most precursors first make FeOOH, which at higher temperature converts to Fe3O4, in absence of open air. If your reaction-temperature is low, you may get FeOOH, instead of Fe3O4.

If you have FeOOH or gamma-Fe2O3 impurities (may commence, if you don't use vacuum-drying), your sample will look brown with a soil-type texture. But, pure Fe3O4 is black, and fine crystalline powder. You should also use surfactants to ensure less surface-oxidation. But, if you use too much surfactant (polymers), Fe3O4 will be inside a polymer matrix, and you may get this sort of noisy and humpy XRD data.

So, in brief, there are so many crucial points. I'll recommend the following paper of mine, it has a grand detailing of synthetic techniques. Also consult the supporting information:

Article Size-modulation of functionalized Fe3O4: Nanoscopic customiz...

Dear Moustafa Abdelaziz ,

Looking at your XRD pattern, I would say the synthesized material is of highly amorphous nature as the peak intensties are very weak. But if you see, definitely there is a peak around 36 which is a characteristic peak of Fe3O4. So you just smoooth the curve so that the major peaks will be clearly visible.

For your refernce I am attaching an article where similar XRD pattern of Fe3O4 has been reported.

Thank you.

I worked with Fe3O4 for quite a long and had gone through this problem in 2018. For iron oxides, synthetic conditions are extremely important. Let me explain why.

Iron oxide and oxyhydroxides have almost 20 different polymorphs, out of which, at least 7 are stable in ambient conditions. During the synthesis procedure, if you accidentally oxidize the system, you'll get gamma-Fe2O3, also known as maghemite. This phase also converts to hematite on open-air heating. If you have a look on the reaction-mechanisms, you'll find, most precursors first make FeOOH, which at higher temperature converts to Fe3O4, in absence of open air. If your reaction-temperature is low, you may get FeOOH, instead of Fe3O4.

If you have FeOOH or gamma-Fe2O3 impurities (may commence, if you don't use vacuum-drying), your sample will look brown with a soil-type texture. But, pure Fe3O4 is black, and fine crystalline powder. You should also use surfactants to ensure less surface-oxidation. But, if you use too much surfactant (polymers), Fe3O4 will be inside a polymer matrix, and you may get this sort of noisy and humpy XRD data.

So, in brief, there are so many crucial points. I'll recommend the following paper of mine, it has a grand detailing of synthetic techniques. Also consult the supporting information:

Article Size-modulation of functionalized Fe3O4: Nanoscopic customiz...

Dear Moustafa Abdelaziz,

I think the material is amorphous. If you still want analyse the pattern then there are two notable peaks around 35 and 65, so try to smoothen the pattern to elevate both peaks. Then do some regular process and compare that with icdd data in XpertHighScore plus.

Also try to calculate %crystallinity then you may get some idea about material.

Dear Moustafa Abdelaziz ,

there is another reference about Fe304 nanoparticles at RG with more pronounced peaks: please see Fig. 1 of:

Article Use of Fe3O4 Nanoparticles for Enhancement of Biosensor Resp...

To my opinion the 'amorphous' background of your pattern may arise from Fe K-fluorescence excited by Cu K-alpha of your x-ray tube.

As Souvik Bhattacharjee stated above, there might be a lot of other Fe compounds present in your sample but only a little Fe3O4; but the Fe atoms of all Fe compounds contribute to the background.

Recommendations:

a) You can reduce this fluorescence background by using a Co based x-ray tube.

Co K-alpha is not able to excite Fe K-fluorescence.

b) Smoothing is an option, but you will propably broaden your peaks. You should go for much larger acquisition time to improve your signal to noise ratio; go for at least 4 times increase of scan time ( better 10 times or even more....).

Good luck

I can see a definete peak near 36 degree which is due to (311) orientation of Fe3O4 phase but the intensity is very low. Generally this peak appears with highest intensity along with series of peaks for Fe3O4 nanoparticle. In your case this peak is so small and missing of other peaks indicating the very poor crystallinity of the material.

Dear Moustafa Abdelaziz,

If you have used some surfactant or some chemical/bio-synthetic procedures, then you may think of a high temperature calcination depending on the thermal stability of the Fe3O4. On performing the calcination, you would obtain a better crystallinity. Typically a calcination at 250oC for 2 hours should be enough. Also, if the size of the nanoparticles are very small (typically quantum dots) then you may get such an XRD. In such a case, XRD won't be suitable for the crystal analysis.

Dear Moustafa Abdelaziz,

Based on the procedure and conditions of preparation your Fe3O4 samples, the amorphous phase is high. Beside the polymorphs property of Fe3O4 play a rule in the resultant structure. Layer of native oxides could be covered the surfaces of Fe3O4 nanoparticles. You may try to in-situ and ex-situ minimize exposure samples to air before XRD examination.

Dear Moustafa Abdelaziz ,

as alternative of using a Co x-ray tube you may use a balanced filter set ( Ross-filter) of for example 5µm Ni and 5,5µm Co.

Please put these filters alternaltely in front of the detector and acquire your XRD pattern; for example patternNi with Ni filtration and patterCo with Co filtration.

The resulting patternRes, which mainly is due to Cu K-alpha radiation, but most of the Fe K-fluorescence removed, is calculated via:

patternRes = patternNi - patternCo

Good luck

Dear Moustafa Abdelaziz

I suugest you to follow the procedure in these two articles, as you can find the typical peaks for such Fe3O4 nanoparticles.

You can also have a look at the attached figures, and if you need further help, let me know. My Regards

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I agree with Gerhard Martens, it could be an instrumental problem, have you used enough quantity on your sample holder or you used a substrate? This diffractogram is typical of nano iron oxides prepared in the presence of organic compounds where the amorphous fraction will be high and the mean particle size is really small (let's call them amorphous iron oxides), you can try to remove the background using TOPAS or MATCH, then the answer will be if you have prepared stoichiometric maghemite or magnetite NPs? XRD is not enough to differentiate. I have eight years working on nanomagnetite/nanomaghemite and the synthesis method will be a key to differentiate them. The above affirmation that crystallinity in that samples are all single-crystallinity is wrong. (311) Miller index is not enough to estimate the "crystallite" size of your NPs, Scherer is a method from the past century and in principle, it will not give you an accurate mean crystallite size if you only have one Bragg's position. Try to improve your synthesis first and then you will be able to characterize your sample correctly. Moreover in the paper shared above (Dalton Trans.,2020,49,7872–7890), that Mossbauer spectra at 300 K do not corroborate the presence of pure Fe3O4. All my best.

I have phased the same issue during my work on Ferrites. A little factor generates a different phase during synthesis and secondly Fe3o4 is a very unstable structure in ambient condition. You should be very careful about synthesis protocol for this and especially choosing capping agent.