What should be a good sample preparation methodology for obtaining good quality EBSD patterns in Ceramics, such as Non-oxide ceramics (especially Carbides and Borides)? There are a few queries in specific, as follows:
1. There are places in literature which say that even Fractured surfaces can be looked at for obtaining good patterns but I haven't been successful with that.
2. Can techniques like Electro-polishing be tried on these ceramics (similar to Metals and alloys, because this class of ceramics is also conducting in general)?
3. I have even tried Vibro-Met polishing for around 10 hours but only 50% of area is getting indexed.
1. For brittle materials fracture surfaces are perfect since you do not invent any additional preparation artifacts. A claevage plane of a feldspar or calcite will form practically ideal patterns. For ductile materials it is of course problematic. And the surface roughness after fracture is terrible under 70 degree tilt so that single pattern are OK but maps are typically out of any discussion.
2) electropolishing avctually only works with conductive materials, i.e. for the matrix but not for the precipitates. On the other hand, the precipitates also form nice patterns because they are mostly free of any lattice defects. As long as the electropolishing does not affect them negatively they can be measured as well. For real ceramic phases it won't work.
3) Vibro-met is from my point of view totally overestimated. Of course, for materialys require a small loading during preparation it is better to do this in a vibro-met, but frankly speaking we did not have that many cases. We are doing all manually although we have automated polishing mashines. You simply feel during polishing if something is going on. If you have many samples with the same material it is of course more efficient to move to an automated procedure, but if you have many different samples the manual procedure is usually faster end more efficient. For hard phases you perhaps have to increase the loading, or to increase the time.
To be honest, your experience looks strange, as we've never had any problems in obtaining high quality EBSD patterns from any non-oxide (carbide, boride, nitride, sialon) ceramics fractured surfaces in any SEM. However, to give you any advice in electropolishing/electroetching it is necessary to know exactly the composition of your materials, as e.g. refractory carbides in such conditions behave very different from each other...
I seem to remember getting excellent EBSD patters with polycrystalline calcite with just manual polishing with Colloidal silica, after the usual polishing steps. In terms of manual polishing at least there are no hard & fast rules. I tried tweaking with the composition of C.S by just adding distilled water in varying proportion to see which works best. If you have two phases with differential chemical attack rates from C.S, I found that the 20nm Buelher master met solution works best, otherwise the Struers 50nm OPS solution works great. I would say manual polishing for an hour or two would typically suffice. You can also attempt FIB polishing at low currents, my colleagues used to get good results with it on oxides, see no reason it shouldn't work for other ceramics.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Ceramics