Phase Evolution oF Tin Oxides Roasted Under CO-CO2 Atmospheres in the Presence of Na2CO3

High-purity Na2SnO3 has been prepared by a novel process of roasting SnO2 and Na2CO3 in a solid state under CO-CO2 mixed gas. In the current study, the phase evolution of tin oxides and Na2CO3 roasted under various CO-CO2 atmospheres was investigated by chemical and X-ray diffraction analysis. Under the CO content of 5-20 vol% and temperature over 800 degrees C, Na2CO3 can react with SnO2 and the intermediate products of SnO and Sn to form Na2SnO3. SnO would be decomposed into SnO2 and Sn at temperatures below 800 degrees C; however, the decomposition reaction was effectively restrained by Na2CO3 over 800 degrees C. Na2CO3 apparently inhibits the volatilization of SnO. The reaction mechanism of SnO and Na2CO3 under reductive atmosphere was clarified.