Characterization studies of physicochemical modifications conceded by equimolar-mixed chromia and barium carbonate powders as a function of temperature

Occurrence and products of solid/solid interactions in equimolar-mixed BaCO3 and Cr2O3 powders were examined isothermally (700–1000 °C) and non-isothermally (25–1200 °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 non-catalytic decomposition of the barium carbonate commenced at 570 °C, a temperature that is much less than the decomposition temperature (≥970 °C) of separate BaCO3. Characteristics and distribution of the yielding products were found to be quite sensitive to the surrounding gas atmosphere. Under N2 atmosphere, the interactions were thermochemical in nature, leading eventually to the formation of barium chromite (BaCr2O4) spinel as the sole detectable product. Under O2 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.