General thermodynamic considerations for the chemical transport of ternary compounds; chemical transport of yttrium iron garnet with HCI

Abstract

Thermodynamic considerations are applied to the problem of the chemical transport of ternary compounds. While many ternary compounds have been transported with satisfactory results, difficulties have been reported in the case of certain oxides especially garnets and some spinels. A general scheme has been developed to evaluate the conditions under which a ternary phase may become unstable and decompose into the binary compounds. These considerations have been applied to the chemical transport of yttrium iron garnet (YIG) with HCl as a transport agent. Normally YIG decomposes during this reactions. Under certain conditions predicted thermodynamically, however, single crystals of YIG up to 5 mm in size were transported in a closed system. The extension of the general scheme from ternary to quarternary and higher compounds is proposed.