Rapid synthesis of Pb_5(VO_4)_3I, for the immobilisation of iodine radioisotopes, by microwave dielectric heating

摘要

Rapid synthesis of Pb_5(VO_4)_3I, a potential immobilisation host for iodine radioisotopes, was achieved in an open container by microwave dielectric heating of a mixture of PbO, PbI_2, and V_2O_5 at a power of 800 W for 180 s (at 2.45 GHz). The resulting ceramic bodies exhibited a zoned microstructure, differentiated by inter-granular porosity and phase assemblage, as a consequence of the inverse temperature gradient characteristic of microwave dielectric heating. Liquid PbI_2 within the interior of microwave processed ceramics assisted formation of Pb_5(VO_4)_3I, and reduced inter-granular porosity. In contrast, the exterior of microwave processed ceramics comprised poorly sintered Pb_5(VO_4)_3I with the presence of minor reagent relics. Quantitative microanalysis, electron diffraction and Rietveld analysis, confirmed the synthesis of stoichiometric Pb_5(VO_4)_3I within precision. The crystal structure of Pb_5(VO_4)_3I was found to adopt space group P6_3/m with a = 10.4429(3) and c = 7.4865(2).