Thermal properties of europium nitrate hexahydrate Eu(NO3)3·6H2O

The hexahydrate of europium nitrate hexahydrate Eu(NO3)3·6H2O shows no phase transitions in the range of −40 to 76 °C when it melts in its own water of crystallization. It was shown that the thermal decomposition is a complex step-wise process, which starts with the simultaneous condensation of 6 mol of the initial monomer Eu(NO3)3·6H2O into a cyclic cluster 6[Eu(NO3)3·6H2O]. This hexamer gradually loses water and nitric acid, and a series of intermediate amorphous oxynitrates is formed. The removal of HNO3 azeotrope is essentially a continuous process occurring in the liquid phase. At higher temperatures, oxynitrates undergo further degradation, lose water, nitrogen dioxide, and oxygen, and finally, after having lost lattice water, are transformed into europium oxide. All mass losses are satisfactorily accounted for under the proposed scheme of thermal decomposition.