The thermal decomposition of lanthanum(III), praseodymium(III) and europium(III) nitrates

The thermal decomposition kinetics of some anhydrous lanthanide nitrates were investigated and compared with those of neodymium nitrate. The kinetics of the decomposition reaction of La(NO3)3 and Pr(NO3)3 are described by the contracting area and contracting volume mechanism, respectively. The enthalpy of decomposition amounts to 123.4 and 102.6 kJ mol−1, respectively. No reversible changes were observed for these two nitrates. The decomposition reaction of Eu(NO3)3 is similar to that of Nd(NO3)3 in so far as a reversible change occurs simultaneously with the decomposition reaction, causing a change in the temperature dependence of the rate constant. The enthalpy of decomposition was estimated as 119.6 kJ mol−1. Decreasing ionic size of the metal ions appears to decrease the thermal stability of the nitrate, as manifested by the values of the temperature of initiation of decomposition.