Studies in the System Li2O–Al2O3–Fe2O3‐H2O

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Abstract
Subsolidus equilibrium relations in a portion of the system Li2O‐Fe2O3‐Al2O3 in the temperature range 500° to 1400°C. have been determined near po2= 0.21. Of particular interest in this system is the LiFe5O8‐LiAl5O8 join, which shows complete solid solution above 1180°C. Below this temperature the solid solution exsolves into two spinel phases. At 600°C. approximately 15 mole % of each compound is soluble in the other. The high‐temperature solid solution and the low‐temperature exsolution dome extend into the ternary system from the 1:5 join. There is no appreciable crystalline solubility of LiFeO2 or of α‐Fe2O3 in LiFe5O8. An attempt to confirm HFe5O8 as the correct formulation of the magnetic ferric oxide “γ‐Fe2O3” was inconclusive, but in the absence of positive evidence, the retention of γ‐Fe2O3 is recommended. All the metallic oxides of the Group IV elements increase the temperature of the monotropic conversion of ‐γ‐Fe2O3 to α‐Fe2O3. Silica and thoria have a greater effect on this conversion than does titania or zirconia.