X‐Ray Study of the Solid Solution of TiO, Fe2O3, and G, O3 in Mullite (3A12O3a2Si02)

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Abstract
A study of the solid solution of TiO2, Fe2O3, and Cr203 in mullite was made by measuring the changes in lattice parameters and unit‐cell volume. Synthetic mullite (3O3‐2SiO2) was reacted with up to 12 weight % of the oxides at temperatures ranging from 1000° to 17000C. The approximate minimum temperature required for the formation of solid solution was 12000C. for Fe203 and 1400°C. for Cr2O3 and TiO3. The maximum amount of solid solution found was 2 to 4% TiO2 at 1600°C., 10 to 12% Fe2Os at 1300°C., and 8 to 10% CrZO3 at 1600OC. Lattice parameters and unit‐cell volumes for each solid solution series increased with increasing amounts of foreign oxide. There was good agreement between the calculated and observed increase in cell dimensions for the iron oxide series. Except in the case of titania, there was good agreement between X‐ray data and petrographic observations.