I have prepared phase pure BiFeO3 with particle size 20 nm by hydrothermal method. But FESEM shows lot of agglomeration. Tried mortaring and ultrasonication. But of no use. What can I do to get segregated particle image.
Agglomeration should be simply broken by mechanical forces, otherwise, the particle is strongly collected (aggregation). It can be distinguished from the images whether the particles are interconnected or not.
If the aggregation is not the case, disperse the particles in a volatile solvent (e.g. Ethanol) to obtain a very diluted suspension. Then drip a drop of the suspension on a tiny glass plate. Put the plate in an oven (e.g. 40 oC) for quick evaporation of the solvent. Finally, submit the sample for FE-SEM analysis.
If the suspension is not diluted enough, in the image you will see a bunch of particles!
I agree with Ali Nematollahzadeh.
You can ressuspend you nanoparticles in a solvent with lower boiling temperature, and deposite the suspension drop-by-drop on you holder.
But to dry, i recommended the use of low pressure conditions, to avoid effect of coffe ring and others process of aggregation.
Fahmida Sharmin
You do not say what form (powder or colloidal suspension) you material is in but I suspect powder from the hydrothermal route. If it's in powder form then you have no free, independent, discrete particles of < 100 nm present. How did you obtain 20 nm as a particle size? Do you mean crystallite size? With a density of 8.22 g/cm3 then your specific surface area should be around 2500 m2/g. Have you measured this crucial parameter? In powder you'll have a collection of fused, chemically bound, aggregates (not dispersible) and looser agglomerated (dispersible by sonication in the wet, for example). See (registration required):
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
If your material is in colloidal suspension and 20 nm, then you should have a clear (maybe colored) transparent liquid. Here there are a number of preparation techniques for SEM or TEM and you may wish to look at 2 NIST materials (RM 8011 and 8012) in this size region. For the smaller SM 8011 (TEM ~ 9 nm) you'll find the electron microscopy preparation routes on page 7 and for 8012 (TEM ~ 28 nm) on pages 7 and 8.
@Alan F Rawle thank you very much for your answer. 20 nm is the particle size of my powder material. I have calculated that from FESEM images, particles are not segregated but could be seen individually for calculation. I have not yet measured the surface area.
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