The initial retentions (at ∼20°C) of (n, γ) activated rare earth bromates were studied using a252Cf fission neutron source with respect to80Br,80mBr and82Br. They lay over the ranges 19–23, 21–23 and 28–32%, respectively. On heating, retention progressively increases and closes
on ∼100% for Sm-bromate while for other systems the optimum values reach <85%. Thus, cation effect becomes more pronounced
during thermal annealing. The isothermal data show that the weight-loss is due to dehydration. The cation effect on retention
is discussed in the light of various parameters like lanthanide contraction, crystal structure, lattice energy, crystal water,
properties of anion and mode of thermal decomposition.