RE2Zr2O7 and related oxides containing rare earth elements should be sintered at temperature ca 1500-1600oC in order to obtained pellets with high relative density. However at this temperature range RE tend to react with Al2O3 which is common materials for a crucible. What is the best way to sinter such materials? Are any powders used to separate pellet from crucible?
If you sinter the material in a vacuum or hydrogen furnace, you can take simply a crucible made of molybdenum foil.
Use some coarse alumina powder to separate the samples from the crucible and from each other. There were some previous similar threads on RG on related topics
RE2Zr2O7 and related oxides have low thermal conductivities, to chose the sintering conditions, please try to avoid cracking during cooling. Usually, very low cooling rate is needed.
To prevent the reaction of RE with crucibles , one the one hand, you may use RE2Zr2O7 and related oxides powders by brushing them on surfaces of pellets; on the other hand, you can use MgO or ZrO2 crucibles.
You can use coarse powders of zirconia (heat treated at higher temperatures, e.g. arc-melted previously and then ground) to separate your pellets from crucible. However, for better results in the preparation of homogeneous composition you need to process your material through double-sintering: after the first sintering cycle to grind the obtained products and repeat everything from the begining (also be careful with choice of materials for balls and mill surfaces in your ball-milling procedures!).
Thank you for all the answers. The powders I use are synthesized via chemical process so homogeneity is not an issue. So if I have nanometric zirconia it would be good idea to pre-heat it before use as inert powder in order to obtain coarser grain?
As I know, a lot of researchers use commercial ground Baddeleyite for this purpose. In my opinion it is easier and cheaper...
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