Thermodynamic and High-temperature Recovery Kinetics of Irradiation Defects in Neutron-irradiated 6H-SiC

doi:10.15541/jim20250216

Abstract

Abstract: Silicon carbide (SiC) is a promising material for nuclear reactor structures due to its excellent radiation resistance and high-temperature performance. The behavior of irradiation damage and the mechanisms of high-temperature recovery in SiC directly affect its service performance and longevity in nuclear environments. This study systematically investigated the effects of neutron irradiation on the properties of 6H-SiC, with a particular focus on the high-temperature recovery mechanisms of irradiation-induced defects. Specifically, defect evolution and thermodynamic responses in nitrogen-doped (N_D ≈ 3.0×10¹⁹ cm⁻³) 6H-SiC subjected to neutron irradiation (irradiation temperature~150 ℃, fluence 2.58×10²⁰ n/cm²) followed by isochronal annealing were examined. Integrated techniques and first-principles calculations were employed to comprehensively analyze structural and property evolution. The key findings of our study were as follows: (1) Significant lattice swelling was observed during irradiation, with swelling rates of 0.416% along the a-axis, 0.430% along the c-axis, and a 1.310% increase in the unit cell volume, all while maintaining the integrity of single-crystalline structure. (2) A 14.7% increase in specific heat capacity was recorded, with 375.4 J/g of stored irradiation energy being released during heating from 100 ℃ to 500 ℃. (3) a four-stage defect recovery kinetic model was proposed based on the recovery of lattice parameters and the evolution of Raman spectra: Stage I (RT-600 ℃): This stage is primarily dominated by the close-range recombination of carbon Frenkel pairs, with a migration energy (E_a) of approximately 0.14 eV. Stage II (600-850 ℃): This stage involves the recombination of silicon Frenkel pairs and the migration of carbon interstitials (E_a ≈ 0.26 eV). Stage III (850-1200 ℃): Lattice reconstruction driven by vacancy migration occurs, with a migration energy of approximately 0.65 eV. Stage IV (1200-1500 ℃): This stage is characterized by long-range diffusion of carbon vacancies (V_C) and the dissociation of N_CV_Si complexes, with a migration energy of approximately 1.5 eV. (4) Raman and photoluminescence spectroscopy confirms the presence of nitrogen-stabilized N_CV_Si defect configurations, which exhibit a characteristic emission peak at 826 nm (634 cm⁻¹ Raman shift) when excited with 785 nm light. This study quantitatively reveals the defect recovery pathways and migration energies in neutron-irradiated 6H-SiC, thereby enhancing understanding of its thermodynamic responses and high-temperature recovery kinetics. It provides a critical foundation for evaluating radiation damage, predicting performance, and optimizing annealing processes in nuclear-grade SiC materials.

Key words: irradiation-induced energy storage, specific heat, Raman spectroscopy, defect luminescence, Arrhenius

CLC Number:

ZHU Fei, HAO Xujie, ZHANG Quangui, YAN Xinyue, LIU Hongfei, ZHANG Bo, LI Xin, LIU Defeng, TUO Yayong, ZHANG Shouchao. Thermodynamic and High-temperature Recovery Kinetics of Irradiation Defects in Neutron-irradiated 6H-SiC[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250216.

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