Investigation of the sintering of barytocalcite with BaCO3 as a secondary phase for immobilizing carbon-14

The effect of a secondary phase (BaCO3) on the sintering of synthetic barytocalcite has been investigated. It was found that this phase impacts the sintering positively by lowering the sintering activation energy from 230 to 160 kJ mol−1, by increasing the shrinkage rate and by reaching higher densities. However, BaCO3, originally dispersed in the powder, was segregated by diffusion during sintering with a large part of it being located at the grain boundaries. The dense pellet is made of both phases barytocalcite and BaCO3, what should be avoided to give the best leaching resistance. Thus the BaCO3 presence should be limited as much as possible by controlling the reactants stoichiometry during the synthesis.