"Strong XRD peaks" tell you either (1) your sample is neither amorphous nor nano crystalline; or (2) the sample is fine but you are getting strong diffraction peaks from the sample holder.

Dear Sreeja Narayanan,

Plz specify that which type of material you are talking about, only than I can help U.

All the Best.

Are you sure that the peaks arise solely from the NPs and not from the substrate or the sample support?

In addition to the request on material information by Qaisar above you may share the diffractograms.

"Strong XRD peaks" tell you either (1) your sample is neither amorphous nor nano crystalline; or (2) the sample is fine but you are getting strong diffraction peaks from the sample holder.

It is advisable to identify the unknown "strong peak" before advancing to the next level. It can either be from the background or your sample is no amorphous/nano-crystalline.

Dear Sreeja,

It is obvious that your hypothesis must be wrong. If you’re certain about amorphous nature of your bulk sample, make sure that your powder irradiated throughly by x-rays. Otherwise diffraction peaks may related with sample holder.

If we trust your experimental setup is all right, there are few possibilities left for logical explanation of your experiment. For example, If you made experiment at air, you need to check your sample’s stability with air or humidity. You may not be realize in bulk form due to small surface area you got thin reaction layer but when you pulverize your sample you created very large surface in comparison with bulk form. That increases the reaction time or speed, and increases amount of reaction products inevitably. reaction products may be crystalline form so you actually measure them instead of your amorphous sample.

I hope this idea could help you.

Good luck.