The third step, from 500 to 900◦C, was due to the loss
of CO2 molecules. In this step, the carbonates (SrCO3,
MnCO3) and oxycarbonate (La2O2CO3) were decomposed
into La2O3, SrO, and MnO with emission of CO2 corresponding
to the mechanism of decomposition as follows
[11]: