On the effect of oxygen partial pressure on the chromium distribution coefficient in melt-grown ruby crystals

TL;DR

This study investigates how oxygen partial pressure influences chromium distribution in melt-grown ruby crystals, revealing a linear relationship and thermodynamic insights into the growth process.

Contribution

It provides new experimental data showing the dependence of chromium distribution coefficient on oxygen partial pressure in ruby crystal growth.

Findings

Chromium distribution coefficient varies from 0.3 to 1.2 with oxygen pressure.

k depends approximately linearly on log(p(O2)).

Thermodynamic calculations support experimental observations.

Abstract

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.