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

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.

Caracterización por XANES, análisis mineralógico y aplicación industrial de un depósito de caolín de México

“…Así, el blanqueo del material observado en el intervalo de 1.200-1.450 ºC es paralelo a la formación de la mullita. De acuerdo a trabajos previos (17), la mullita tiene la capacidad de incorporar cerca del 10-12% de hierro como Fe 2 O 3 a través de un mecanismo de formación de solución sólida. Caracterización por XANES, análisis mineralógico y aplicación industrial de un depósito de caolín de México A Mexican kaolin deposit: XANES characterization, mineralogical phase analysis and applications cambio energético también se refleja en el análisis por DTA.…”

Effect of transition-metal-ion doping on high temperature thermal expansion of 3:2 mullite—An in situ, high temperature, synchrotron diffraction study

“…2 According to past reports, up to 12 wt.% Cr 2 O 3 could be incorporated into mullite. 20,23,29 In this study, up to 15.9 wt.% Cr 2 O 3 was successfully incorporated in mullite. We believe that this was achievable primarily due to the more efficient mixing at molecular levels afforded by the co-precipitation method (PVA steric entrapment method) used for sample synthesis in this study.…”

“…2,28 While the highest degrees of incorporation were observed for trivalent cations such as V 3+ , Cr 3+ and Fe 3+ (approximately 11-13 wt.% as oxides) followed by Ti 4+ , and V 4+ (2-6 wt.% as oxides), only very low amounts of Mn 2+ , Fe 2+ and Co 2+ ions (<1 wt.% as oxides) entered the mullite structure. 2,15,19,20,23,28,29 Mullites display low and non-linear thermal expansion below ∼300 • C; and larger linear expansion between 300 • C and 1000 • C. Beyond 1000 • C, up to 1300 • C, an observed discontinuity in thermal expansion behavior has been attributed to a phase transformation, but is not completely understood. 2,30 Schneider and Eberhard, 14 and later Brunauer et al 13 showed that incorporation of Cr 3+ and Fe 3+ (11.5 wt.% and 10.3 wt.%, respectively) in mullite resulted in a decrease in thermal volume expansion.…”

Low-temperature Ti-containing 3:2 and 2:1 mullite nanocrystals from single-phase gels

“…23,24 Some results on the solubility of titanium oxide in 3:2 mullite synthesized by conventional laboratory techniques have already been reported but data on the role played by the titanium oxide during the reaction sequence at low temperature in 3:2 mullite monophasic gels are still scanty. [25][26][27][28][29] Thus, it seems to be interesting a systematic study concerning the mullitization of titanium-containing 3:2 mullite monophasic gels. Likewise, it would be also valuable to extend the study to 2:1 mullite single-phase gels, in order to compare thermal behaviours of either end-member of mullite gels.…”