Thermal behavior and stability of eutectic 52/48 Li/Na carbonate mixture containing various concentrations of lanthanum carbonate in the range 0.5-2.0 mol% was investigated by a combination of thermal analysis (DSC) and spectroscopic (EGA-FTIR) techniques under CO2 and N-2 gas flows. Thermal decomposition of lanthanum carbonate with CO2 gas release was observed in the 470-480 degrees C range close to the melting point of eutectic alkali carbonate giving raise to formation of lanthanum oxycarbonate species. It was also found that the lanthanum carbonate phase promptly reformed, when the eutectic carbonate melt samples were cooled down to 440-460 degrees C under CO2 atmosphere. (C) 2012 Elsevier B.V. All rights reserved.