It is well known that heat treatment enhances the cristallinity of materials. This means that you will have an increase in XRD peaks intensity. Also, you may have an increase of the cristallite size. This could be clearly visible from the narrowing of your XRD peaks.
I studied nano/micro-sized powder calcinated at different temperatures. I could see a trend on XRD pattern that when the calcination temperature was increased while processing these powders, intensity of the characteristic peaks increased with it.
I also studied these powders under SEM, but couldn't concluded any noticeable difference. Different imaging technique should be considered while studying their differences in nano/microstructure and morphology.
For my best of knowledge, the stability of the NPs is the top most problematic area. Definitely differences will be there. Agree with Prof. Artur's view. Plz explain that first.
I believe the increase in intensity of the characteristics peaks is because of the increasing crystallinlity of the material as a result of heat treatment.
Usually, increasing the annealing temperature leads to increasing the degree of crystallinity. So, In most cases, we find that the X-ray diffraction lines increases with rising the annealing temperature.