crystal cluster problem

ruyle at dallas.net ruyle at dallas.net
Sat Jun 13 18:00:37 EST 1998


yep. your seeing the tendancy of molecules to move from warm places to
cooler places.
as nucleation begins. the formed crystal represents a "cooler" place
than the areas around it. and as such attracts further nucleation.
you need to do 2 things.
1. encourage growth of the crystal your trying to grow.
provide a highly polished and correctly oriented seed crystal for your
nucleation to take place on. make sure its the coolest place in the
crucible. cooling it by a few degrees is more than sufficient.
2. discourage all other growth.
attempt to maintain an even temperature throughout the rest of the
solution. (as far as possible), and provide agitation of the solution.
a growing crystal on the end of a rotating seed makes an exellent paddle
to do this with. not only does it help nucleation by replacing the
depleted solvent at the crystal/solvent boundary with fresh nutirent, it
helps stop the formation of the clusters by agitation of the solvent.
i have tried various rotation speeds and various solvents. it seems that
around 18 rpm is just fine. above 25 causes too many inclusions in the
growth.
give it a try
hope it works.
did for me.
steve ruyle




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