JOURNAL OF SOLID STATE CHEMISTRY 88, 351-367 (1990) The Chemistry of the Thermal Decomposition of Pseudobrookite Ferrous Titanium Oxides RAYMOND G. TELLER AND MARK R. ANTONIO BP Research, Warrensville Laboratory, 4440 Warrensville Center Road, Cleveland, Ohio 44128-2837 ALPHONSO E. GRAU AND MICHEL GUEGUIN QIT-Fer et Titane Inc., P. 0. Box 560, Sorel, Quebec Canada J3P 5P6 AND EDWARD KOSTINER Department of Chemistry, University of Connecticut, Storrs. Connecticut 06269 Received February 12, 1990; in revised form May 11, 1990 The thermal decomposition of two metastable ferrous titanium oxide compounds of commercial interest have been studied by in situ X-ray and neutron diffraction at elevated temperatures as well as by “Fe Mossbauer effect spectroscopy. Thermal decomposition was monitored by collecting neutron diffraction data (taken at the Argonne National Laboratory Intense Pulsed Neutron Source (IPNS) powder diffractometers) at 30-min intervals at 900 and 1000°C.Previous work has shown that each of these materials (pseudobrookite structure, A&O& (Mneos Fe,3;Tio.s2)(Ti,o)OS and ~~&d%.33%~d- (Ti,.gM&,,)Os, has a significant amount of Ti in the + 3 oxidation state and is completely ordered (no Fe located in the “B” site). The results of these “in situ” diffraction studies show that, prior to the thermal decomposition of the slags, there is a redistribution of cations within the pseudobrookite structure. Specifically, at temperatures in the range 600-7OO”C, iron cations move from the “A” sites to the “B” sites and Ti cations move from the “B” to the “A” sites. It is after this order-disorder transition that decomposition commences. At temperatures above 9OO”C, the neutron diffraction data show at least two modes of decomposition describing the high temperature chemistry of these disor- dered materials. The first mode produces iron metal and rutile (TiO,) and is modeled by the equation 2Fe,,5Tiz,,0S+ Fe + STiO?. The second mode of decomposition produces an iron-doped titanium oxide of the rutile structure and is modeled by the equation 4M,,3Ti2,705 + 2M0,5Ti,,505+ 5Feo,,Ti,.,h02 (M = Fe*+, Mn*+, Mg’+). 0 1990 Academic Press, Inc. Introduction noted that the temperature of preparation and the conditions of reduction largely de- During the course of structural investiga- termined the distribution of metal atoms tions of ferrous titanium oxides with the within the AB,O, structure. Neutron diffrac- pseudobrookite (A&O,) structure (I), it was tion and S7FeMossbauer effect spectros- 351 0022-4596190 $3.OO Copyright 0 1990 by Acidemic Press, Inc. All rights of reproduction in any form reserved.