Thermal conductivity of self-ion irradiated nanocrystalline zirconium thin films

Thermomechanical stability and high thermal conductivity are important for nuclear cladding material performance and reliability, which degrade over time under irradiation. The literature suggests nanocrystalline materials as radiation tolerant, but little or no evidence is present from thermal transport perspective. In this study, we irradiated 10 nm grain size zirconium thin films with 800 keV Zr⁺ beam from a 6 MV HVE Tandem accelerator to achieve various doses of 3 × 10¹⁰ to 3.26 × 10¹⁴ ions/cm², corresponding to displacement per atom (dpa) of 2.1 × 10^− 4 to 2.28. Transmission electron microscopy showed significant grain growth, texture evolution and oxidation in addition to the creation of displacement defects due to the irradiation. The specimens were co-fabricated with micro-heaters to establish thermal gradients that were mapped using infrared thermometry. An energy balance approach was used to estimate the thermal conductivity of the specimens, as function of irradiation dosage. Up to 32% reduction of thermal conductivity was measured for the sample exposed to a dose of 2.1 dpa (3 × 10¹⁴ ions/cm²).