Heavy ion irradiations on synthetic hollandite-type materials: Ba_1.0Cs_0.3A_2.3Ti_5.7O₁₆ (A=Cr, Fe, Al)

The hollandite supergroup of minerals has received considerable attention as a nuclear waste form for immobilization of Cs. The radiation stability of synthetic hollandite-type compounds described generally as Ba_1.0Cs_0.3A_2.3Ti_5.7O₁₆ (A=Cr, Fe, Al) were evaluated by heavy ion (Kr) irradiations on polycrystalline single phase materials and multiphase materials incorporating the hollandite phases. Ion irradiation damage effects on these samples were examined using grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). Single phase compounds possess tetragonal structure with space group I4/m. GIXRD and TEM observations revealed that 600 keV Kr irradiation-induced amorphization on single phase hollandites compounds occurred at a fluence between 2.5×10¹⁴ Kr/cm² and 5×10¹⁴ Kr/cm². The critical amorphization fluence of single phase hollandite compounds obtained by in situ 1 MeV Kr ion irradiation was around 3.25×10¹⁴ Kr/cm². The hollandite phase exhibited similar amorphization susceptibility under Kr ion irradiation when incorporated into a multiphase system.