Contribution of Raman Spectroscopy to The Understanding of Defect Formation Mechanisms

Ion accelerators have been used for decades to study radiation damage in nuclear materials, simulating their behavior in reactors. The diversity of irradiation conditions (ions, energy, fluence, temperature, etc.) is a major advantage of ion beams. This allows for systematic studies aimed at better understanding defect formation mechanisms and the resulting microstructural evolution. Additionally, the very short irradiation times and the handling of non-radioactive samples significantly reduce the cost and duration of experiments compared to reactor irradiations. The coupling of multiple ion beams, the use of heated/cooled sample holders, and the implementation of in situ characterization open the way for real-time observation of microstructure evolution under various extreme radiation conditions. Among these techniques, Raman spectroscopy provides a quick and non-destructive means to monitor vibrational mode evolution. Under irradiation, structural bands evolve, indicating the level of stress and the local structural disorder. Some bands may also appear, providing information about the level of damage and the type of defects formed.<br/>The JANNuS Saclay platform is equipped with a Raman spectrometer installed in the triple-beam irradiation chamber [1]. This allows for in situ monitoring of vibrational modes when atomic displacements and/or ionizations and electronic excitations are generated within the structure. Studies have thus highlighted the use of Raman spectroscopy in characterizing amorphization mechanisms or phase changes occurring under irradiation [2-4]. In non-amorphizable systems, in situ measurements provide insights into damage kinetics related to the formation of point defects [5].<br/>This paper will focus on several examples illustrating the use of ion beams coupled with Raman analyses to investigate the radiation resistance of current and future nuclear ceramic materials.<br/>[1] S. Miro et al., J. Raman Spectrosc. 481 (2015) 45.<br/>[2] C. Ciszak et al., JNM 485 (2017) 392.<br/>[3] A. Debelle at al., JAP 132 (2022) 085905.<br/>[4] D. Gosset et al., JNM 476 (2016) 198.<br/>[5] G. Gutierrez et al., J. Eur. Cer. Soc 42 (2022) 6633.