Occurrence and products of solid/solid interactions in equimolar-mixed BaCO3 and Cr2O3 powders were examined isothermally (700-1000 degrees C) and non-isothermally (25-1200 degrees C) under different gas atmospheres, employing thermogravimetry. X-ray diffractometry, infrared and Raman spectroscopies. scanning electron microscopy, and energy dispersive X-ray spectroscopy. Irrespective of the gas atmosphere, a noncatalytic decomposition of the barium carbonate commenced at 570 degrees C, a temperature that is much less than the decomposition temperature ( 970 degrees C) of separate BaCO3. Characteristics and distribution of the yielding products were found to be quite sensitive to the surrounding gas atmosphere. Under N-2 atmosphere, the interactions were thermochemical in nature, leading eventually to the formation of barium chromite (BaCr2O4) spinel as the sole detectable product. Under O-2 atmosphere, however, the oxygen molecules contributed oxidatively to the chromite thermal genesis course, thus imposing a topochemical nature to the reaction, leading to formation of BaCrO4, as the major product, and barium chromites (BaCr2O4 and Ba3Cr2O6), as minor products. Proposed reaction pathways and characteristics of products have been presented and discussed. (C) 2008 Elsevier B.V. All rights reserved.