Radiation-induced swelling and amorphization in Ca2Nd8(SiO4)6O2

Specimens of Ca₂Nd₈(SiO₄)₆O₂ were doped with 1.2 wt% ²⁴⁴Cm and the effects of self-radiation damage from alpha decay were determined as a function of cumulative dose. The macroscopic volume of the specimens increased exponentially with dose to a limiting (saturation) value of ～8.0%. The initially crystalline material became completely X-ray amorphous at a dose of 11.7 × 10²⁴ alpha decays/m³. The dissolution rate of the amorphous state was about an order of magnitude higher than the crystalline state. The stored energy of the amorphous state was ～130 J/g. Differential thermal analysis along with isochronal and isothermal-step annealing were used to study the kinetics associated with the thermal recovery of the radiation-induced swelling and amorphization. A single recovery stage associated with recrystallization of the amorphous material was observed and the activation energy was determined to be 3.1±0.2 eV.