For increased resolution in the SEM, use as high a beam energy as possible ( > 20 keV) and as small an aperture as possible, and an in-lens detector if you have one. For high-res work, wait for the vacuum level to also reach < 10^-6 mbar and make sure the stage tilt is zero degrees. It would also help if your SEM machine is a FEG system, not a thermionic source.

If you are looking for more surface detail, use a lower beam energy (< 5 keV) at a shorter working distance, and a secondary electron detector (ET detector on the side of the chamber).

I'm going to guess the pyrochlore nanopowder is somewhat electrically conductive, so you don't need to sputter coat your sample with a metal layer before imaging. If you encounter charging which is affecting image quality, lower the beam energy.

Make sure you correct for astigmatism (and wobble, if you can) at high magnification by focusing on a circular feature or corner first, so that you can hit the optimal focal point. Adjust the scan speed accordingly to correct for any drift/charging at high magnifications.

The best recommendation would be to learn from an experienced user hands-on, if you can.

For increased resolution in the SEM, use as high a beam energy as possible ( > 20 keV) and as small an aperture as possible, and an in-lens detector if you have one. For high-res work, wait for the vacuum level to also reach < 10^-6 mbar and make sure the stage tilt is zero degrees. It would also help if your SEM machine is a FEG system, not a thermionic source.

If you are looking for more surface detail, use a lower beam energy (< 5 keV) at a shorter working distance, and a secondary electron detector (ET detector on the side of the chamber).

I'm going to guess the pyrochlore nanopowder is somewhat electrically conductive, so you don't need to sputter coat your sample with a metal layer before imaging. If you encounter charging which is affecting image quality, lower the beam energy.

Make sure you correct for astigmatism (and wobble, if you can) at high magnification by focusing on a circular feature or corner first, so that you can hit the optimal focal point. Adjust the scan speed accordingly to correct for any drift/charging at high magnifications.

The best recommendation would be to learn from an experienced user hands-on, if you can.

dear Layla Brini

Based from my experiment, 1st time using SEM always desperate. but by the time you used it, you will comfortable to used it and you will get the good image. If the coating is not really helpful, tray to double it or make the coating time little bit longer.

you can make sure, if your SEM is old type (U have been used old JEOL SEM), try to put the SEM in some cold room (I mean really cold room temperature in AC). you will get better image.

Higher KV will give better resolution and crisper images.

The main question is from my point of view, how do you define "quality of SEM images"? You don't say anything about the signal you are using, the used magnification, the applied energy of primary electrons, the beam current, beam size (resolution), the type of SEM (cathode etc., immersion lens etc), attached equipment  like other detectors or anything else, the material you are investigating. The number of factors is quite big, and for practically each of them different options exist in order to improve the derived image using counted electrons. The entire imaging in SEM is always very critical to discuss: Were the conditions during scanning properly chosen so that the derived image really shows me a signal which correlates with the sample surface, or is it more an interference of side effects? Since electron imaging is not really comparable with a light microscope I hardly recommend to keep the image formation in mind! 

and not last

Follow a manual to your SEM. If you have more specific questions, ask them in separate thread, do not forget to mention what specimens and for what purposes you are using

yours

Dear Jakub Jadwiszczak

thanks a lot for your gold pieces of information

Ashraf Alattar thank you so much for helping me understand better the situation