Desr Luo

Try to coat the sample with a thin layer of a conductive coating,i.e.carbon,gold,and so on. This process might help the detector to collect/ acquisit more backscatter electrons of the ceramic ,i.e.,intermetallic, sample,without having to charge the sample.

Also be sure the electrochemical etching method,i.e.,thermal corrosion treatment, was appropriatedly applied to cause relatively deep etching to the gain boundries. The SEM backcatterring images are usually obtained from the bottom of pits,grain boundaries,noches, and so on.

Xuewei Luo,

Thanks for the question. Inherently, detection of the grain boundary by BSE is dependent upon the width of the grain boundary. Typically, grain boundary widths are very very small (a few nm width in ceramics as estimated by Kingery), where typical BSE interaction volumes are 3 orders of magnitude larger (1-10 microns). This does not take into account etching.

As Khaled J. Habib mentioned, please make sure that your sample is coated to mitigate charging, preferably with carbon as this typically yields the best results, although gold and other targets can be used.

Again, echoing the previous answer and knowing that the grain boundary is very small in width, the etching method is absolutely critical to being able to visualize the grain boundaries. Can you provide your etching method? Also, a general reference for great etching practices is Vaner Voort's book, linked below.

Book Metallography, Principles And Practice

Thanks and good luck.

Dear Luo,

Depends on the type, might find a slow rate etchant for the ceramic. Such etchant will react in a faster rate with the boundaries.

Another option is to try to use a mirror detector SEM (FEI newer model have this), or STEM.

We use SEM Hitachi SU8010 Japan，== Thank You！

As mentioned above, the methodology to obtain an adequate contrast will be fundamental, both of the coating and of the etching , I would also add, testing with intermediate or little lower voltages, to help reveal the grain limits and the effect of the etching.