Thermal decomposition of Ln(C2H5CO2)3•H2O (Ln = Ho, Er, Tm and Yb)

The thermal decomposition of Ho(III), Er(III), Tm(III) and Yb(III) propionate monohydrates in argon was studied by means of thermogravimetry (TG), differential thermal analysis (DTA), IR-spectroscopy and X-ray diffraction (XRD). Dehydration takes place around 90 degrees C. It is followed by the decomposition of the anhydrous propionates to Ln(2)O(2)CO(3) (Ln = Ho, Er, Tm or Yb) with the evolution of CO2 and 3-pentanone (C2H5COC2H5) between 300 and 400 degrees C. The further decomposition of Ln(2)O(2)CO(3) to the respective sesquioxides Ln(2)O(3) is characterized by an intermediate plateau extending from approximately 500-700 degrees C in the TG traces. This stage corresponds to an overall composition of Ln(2)O(2.5)(CO3)(0.5) but is more probably a mixture of Ln(2)O(2)CO(3) and Ln(2)O(3). The stability of this intermediate state decreases for the lighter rare-earth (RE) compounds studied. Full conversion to Ln(2)O(3) is achieved at about 1,100 degrees C. The overall thermal decomposition behaviour of the title compounds is similar to that previously reported for Lu(C2H5CO2)(3)center dot H2O.