The natural chrome ore used in refractories such as magnesia chrome bricks is a spinel solid solution consisting of Cr_2O_3, iron oxide, Al_2O_3 and MgO as major components. It is well known that heating of the chrome ore causes oxidization of iron oxide and deposition of sesquioxide. Various researches and literature have been published on the relation of these phenomena to the heating atmosphere and the chemical composition of the chrome ore~(1,2). Among such changes on heating, the influence upon the volume change is particularly important to understand material design and the embrittlement of magnesia chrome bricks during operation. This paper reports an investigation on the influence of atmosphere on the thermal expansion behavior and differences in the mineral produced on heating.
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