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Mixture of Solvents for Crystal Growth

IP.com Disclosure Number: IPCOM000050723D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Scheel, HJ: AUTHOR

Abstract

In the growth of a solid solution crystal (e.g., of the type A(1-x)B(x)) from the pure melt, the concentration x is determined by the solidus line of the phase diagram and by the actual temperature. The distribution coefficient, i.e., the ratio of the concentration of one component in the solid to that in the liquid, generally deviates from unity and is given by the phase diagram.

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Mixture of Solvents for Crystal Growth

In the growth of a solid solution crystal (e.g., of the type A(1-x)B(x)) from the pure melt, the concentration x is determined by the solidus line of the phase diagram and by the actual temperature. The distribution coefficient, i.e., the ratio of the concentration of one component in the solid to that in the liquid, generally deviates from unity and is given by the phase diagram.

When the solid solution crystal is grown from a solvent, the distribution coefficient can no longer be simply derived from the phase diagram, it is also dependent on the type of solution (ideal, regular, etc.), the activities of the components A and B in the solution, and the temperature, and in most cases it deviates from unity, leading to inhomogeneous crystals.

A mixture of two (or more) solvents, one giving a distribution coefficient k is greater than 1, the other k is less than 1, can be found to yield an effective distribution coefficient k(eff) equals 1 (or nearly equals 1). Since high- temperature data of solutions are scarce, the distribution coefficients have to be determined experimentally. For gadolinium aluminate with partial substitution of Gd by lanthanum (Gd(1-x) La(x) AlO(3)), for example, the critical mixture of the solvents (PbO and PbF(2)) can easily be taken from the diagram for k(eff)=1 at 37-5% PbO and 62-5% PbF(2).

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