A thermal study of several lanthanide triflates

Five lanthanide triflates, Ln(TfO)(3). nH(2)O, where TfO- = CF3SO3-, Ln = La3+, Nd3+, Sm3+, Gd3+ and Yb3+, and n = 9 and 13, have been prepared and the thermal decomposition processes of these triflates up to 600 degrees C were characterized by means of TG, DTA, XRD. The thermal studies have shown almost all the lanthanide triflates prepared in this study to exist as a stable nonahydrate. During the stepwise dehydration processes, it was found that mono-, di-, tri-, penta-, and heptahydrates were formed. Decompositions were found to be exothermic, and calcinations of these triflates at 600 degrees C resulted in the formation of the corresponding LnF(3). Crystal systems of the trifluorides thus obtained were hexagonal for La, Nd and Sm trifluorides, whereas those of Gd and Yb were found to be orthorhombic. The volatile decomposition products at 600 degrees C were identified by MS, and it was revealed that the over all reaction scheme for the thermal decomposition proceeds as follows: Ln(OTf)(3)-->LnF(3) + 3SO(2) + CO2 + CF3OCF3. (C) 1998 Elsevier Science Ltd. All rights reserved.