Radiation Damage and Thermal Annealing in Tunnel Structured Hollandite Materials

Three tunnel structured hollandite samples (Cs 1.33 Ga 1.33 Ti 6.67 O 16 , Cs 1.33 Fe 1.33 Ti 6.67 O 16 , and Cs 1.33 Zn 0.67 Ti 7.33 O 16 ) with demonstrated thermodynamic stability and chemical durability were synthesized and irradiated by a 1 GeV Au ion beam in order to study effects of B-site dopants on radiation stability. The structural changes induced by radiation were analyzed by complementary characterization techniques at different length-scales, such as powder X-ray diffraction, Raman spectroscopy and neutron total scattering. High-temperature oxide melt solution calorimetry was performed to determine the energy landscape before and after radiation. Together, structural and thermodynamic analyses demonstrated distinctly different radiation responses of the hollandite with different B-site dopants. The hypothesized origin of these differences is the structural feature in the binary oxide form of the respective B-site dopants (e.g., Ga 2 O 3 versus ZnO for Ga and Zn dopants, respectively). Moreover, thermal analysis (i.e., differential scanning calorimetry) was conducted to investigate structural changes from the radiation induced damaged states after thermal annealing. Results of thermal analysis revealed that the annealing-induced structural evolution of the radiation damaged hollandite structure is complex and decoupled at different length-scales. The long-range periodic structure (nanometers) was not recovered after thermal annealing and structural changes over a shorter range (≤ ~3 A) occurred in multiple steps during the annealing process.