Thermal decomposition as a preparative route to anhydrous rare earth nitrates

Thermal decomposition of rare earth pentanitrato complexes has been studied by TG and DTA. M2Ln(NO3)5·nH2O (M=NH4, Ln=La, Nd, Pr) decomposes in air through anhydrous (NH4)2Ln(NO3)5 to Ln(NO3)3, LnONO3 and finally to Ln2O3 above 600°C. When M=K and Ln=La, the intermediate K2La(NO3)5 is remarkably stable and KLaO2is formed at 800°C. Except for Nd, the nonanitrato complex M3Ln2(NO3)9 was detected during the degradation process in both air and nitrogen but its stability range is too narrow to allow its preparative isolation as single phase. For comparison, the TG and DSC curves were recorded for La(NO3)3·6H2O where La(NO3)3 and especially LaONO3 appear as stable intermediates.