  Small ruby crystals were grown by the Czochralski technique in different
atmospheres and their actual chromium content was analysed by a wet chemical
method. The chromium distribution coefficient k was found to be strongly
dependent on oxygen partial pressure p(O2). It ranges from k=0.3 in a reducing
atmosphere to k=1.2 in a slightly oxidizing atmosphere and to a good
approximation k depends linearly on log(p(O2)). The experimental data are
discussed on the basis of thermodynamic equilibrium calculations.

Materials Science