The effect of various additives on the decomposition of sodium carbonate (Na2CO3) was evaluated using temperature-programmed desorption, thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. Incorporation of additives, CaO and Ca(OH)(2), had a significant effect on lowering the decomposition temperature of Na2CO3, while CaCO3, SiO2, and Al2O3 had no effect. The amount of additive, sweep gas flow rate, and heating rate were also found to play a significant role in altering the decomposition temperature of Na2CO3. The formation of a carbonate-type intermediate in the presence of CaO and Ca(OH)(2) may have promoted the decomposition of Na2CO3.