Defect-induced phonon-resonant scattering and its influence on thermal transport of irradiated thorium-dioxide
Saqeeb Adnan, Amey Khanolkar, Zilong Hua, Md Minaruzzaman, Mutaz Alshannaq, Joshua Ferrigno, Timothy A. Prusnick, Miaomiao Jin, J. Matthew Mann, David H. Hurley, Marat Khafizov
Abstract
Thermal transport in proton irradiated thorium-dioxide (ThO2) is investigated. Using a combination of experiments and first-principles computational framework, the role of lattice defects on thermal conductivity is analyzed. A resonant-phonon scattering mechanism beyond the traditionally considered Rayleigh scattering is found to significantly influence low-temperature thermal transport in the presence of irradiation-induced point defects. The existence of localized phonon modes associated with irradiation-induced defects is suggested by the inability of the first-principles based thermal conductivity model—which considers only three-phonon interactions and phonon-defects scattering using the Tamura formalism—to predict the experimental results, unless a resonant scattering mechanism is included. The emergence of additional peaks in the Raman spectra in the proximity of phonon-resonant frequency provides further evidence for the existence of localized modes. Coupled with a microstructure evolution model, this analysis enables more accurate analysis for contrasting the contributions of different phonon scattering mechanisms across all irradiation doses and temperatures.