Abstract
The thermal behaviour of Ln(C3H7CO2)(3) (Ln = Er, Tm, Yb or Lu) was studied in argon from room temperature by means of thermogravimetry and differential thermal analysis up to 1400 degrees C, by infrared spectroscopy, hot-stage optical microscopy and X-ray diffraction. Melting prior to decomposition was observed in all four compounds, but its course depends on the rare-earth element. Decomposition to sesquioxides proceeds via the formation of dioxymonocarbonates (Ln(2)O(2)CO(3)) and release of 4-heptanone (C3H7COC3H7) as well as carbon dioxide (CO2) without evidence for an intermediate oxobutanoate stage. During the decomposition of Ln(2)O(2)CO(3) into the respective sesquioxides (Ln(2)O(3)), an intermediate plateau extending from approximately 550 to 850 degrees C appears in the TG traces. The overall composition during this stage corresponds approximately to Ln(2)O(2.8)(CO3)(0.2), but the state is more probably a mixture of Ln(2)O(2)CO(3) and Ln(2)O(3). The stability of this intermediate state seems to decrease with the mass of the rare-earth elements. Complete conversion to Ln(2)O(3) is reached at about 1100 degrees C. The overall thermal decomposition behaviour of the title compounds is different from previous reports for other rare-earth butanoates.