SOLUBILITY MODEL FOR RARE-EARTH IRON GARNETS IN A PBO-B2O3 SOLUTION

It is shown that the solubility of non-substituted rare-earth iron garnets in a PbO/B2O3 solution can be well described if it is assumed that the different garnet components are dissolved separately. Two descriptions for the liquid are used, a molecular fluid consisting of molecules of PbO, B2O3, Y2O3 and Fe2O3 and an ionic fluid consisting of Pb2+, B3+, Y3+, F e3+ and O2- (Temkin model). The latter description gives good agreement between the measured heat of solution and the enthaply of solution obtained from solubility data. If it is assumed that both the liquid and the solid are ideal mixtures of the end-member components, the solubility of substituted garnets like LaxY3-xGayFe5-yO12 can also be described. From experimental data it may be concluded that the degree of La substitution x is influenced by the degree of Ga substitution y, and vice versa. In addition a relation is obtained for the equilibrium distribution of Ga on tetrahedral and octahedral sites. © 1979.