Structural studies of hollandite-based radioactive waste forms

Hollandites with compositions Ba1.2-xCSxMg1.2-x/2Ti6.8+x/2 O-16, and Ba1.2-xCsxAl2.4-xTi5.6+xO16 (x=O, 0. 1, 0.25) have been synthesised using a modified alkoxide/acetate precursor route. The samples have been sintered using two procedures; hot isostatic: pressing and sintering at ambient pressure. X-ray powder diffraction has shown samples from both systems to form tetragonal hollandites, with little change when pressed by both methods. Cs-133 MAS NMR spectra have been recorded showing the chemical shift in At containing samples to be similar to250ppm, and in Mg hollandites similar to175ppm and 200ppm, with little change when prepared by both methods.